The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and field operations

R. Wood; C. R. Mechoso; C. S. Bretherton; R. A. Weller; B. Huebert; F. Straneo; B. A. Albrecht; H. Coe; G. Allen; G. Vaughan; P. Daum; C. Fairall; D. Chand; L. Gallardo Klenner; R. Garreaud; C. Grados; D. S. Covert; T. S. Bates; R. Krejci; L. M. Russell; S. de Szoeke; A. Brewer; S. E. Yuter; S. R. Springston; A. Chaigneau; T. Toniazzo; P. Minnis; R. Palikonda; S. J. Abel; W. O. J. Brown; S. Williams; J. Fochesatto; J. Brioude; K. N. Bower

doi:10.5194/acp-11-627-2011

Wood, R.;Mechoso, C. R.;Bretherton, C. S.;Weller, R. A.;Huebert, B.;Straneo, F.;Albrecht, B. A.;Coe, H.;Allen, G.;Vaughan, G.;Daum, P.;Fairall, C.;Chand, D.;Gallardo Klenner, L.;Garreaud, R.;Grados, C.;Covert, D. S.;Bates, T. S.;Krejci, R.;Russell, L. M.;de Szoeke, S.;Brewer, A.;Yuter, S. E.;Springston, S. R.;Chaigneau, A.;Toniazzo, T.;Minnis, P.;Palikonda, R.;Abel, S. J.;Brown, W. O. J.;Williams, S.;Fochesatto, J.;Brioude, J.;Bower, K. N.;

2011-01-21 00:00:00

Atmos. Chem. Phys., 11, 627–654, 2011 Atmospheric www.atmos-chem-phys.net/11/627/2011/ Chemistry doi:10.5194/acp-11-627-2011 © Author(s) 2011. CC Attribution 3.0 License. and Physics The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and ﬁeld operations 1 2 1 3 4 3 5 6 R. Wood , C. R. Mechoso , C. S. Bretherton , R. A. Weller , B. Huebert , F. Straneo , B. A. Albrecht , H. Coe , 6 6 7 8 1,* 9 9 10 G. Allen , G. Vaughan , P. Daum , C. Fairall , D. Chand , L. Gallardo Klenner , R. Garreaud , C. Grados , 1 11 12 13 14 8 15 7 D. S. Covert , T. S. Bates , R. Krejci , L. M. Russell , S. de Szoeke , A. Brewer , S. E. Yuter , S. R. Springston , 17 16 18 23 19 20 20 A. Chaigneau , T. Toniazzo , P. Minnis , R. Palikonda , S. J. Abel , W. O. J. Brown , S. Williams , 21 22,8 6 J. Fochesatto , J. Brioude , and K. N. Bower Department of Atmospheric Sciences, University of Washington, Seattle, USA UCLA, Los Angeles, USA Woods Hole Oceanographic Institution, USA University of Hawai’i, Honolulu, USA Rosenstiel School of Marine and Atmospheric Science, University of Miami, USA School of Earth, Atmospheric and Environmental Sciences, University of Manchester, UK Brookhaven National Laboratory, Upton, USA NOAA Earth System Research Laboratory, Boulder, USA Departamento de Geoﬁsica, Universidad de Chile, Chile Instituto del Mar del Peru, ´ Peru ´ NOAA Paciﬁc Marine Environmental Laboratory, Seattle, USA Dept. of Applied Environmental Science (ITM), Stockholm University, Sweden Scripps Institution of Oceanography, University of California, San Diego, USA Oregon State University, Corvallis, USA North Carolina State University, Raleigh, USA Department of Meteorology, University of Reading, UK L’Institut de Recherche pour le Dev ´ eloppement, Marseille, France NASA Langley Research Center, Hampton, USA The Met Ofﬁce, Exeter, UK National Center for Atmospheric Research, Boulder, USA University of Alaska, Fairbanks, USA Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA Science Systems and Applications, Inc., Hampton, USA currently at: Paciﬁc Northwest National Laboratory, Richland, USA Received: 4 August 2010 – Published in Atmos. Chem. Phys. Discuss.: 1 September 2010 Revised: 21 December 2010 – Accepted: 29 December 2010 – Published: 21 January 2011 Abstract. The VAMOS Ocean-Cloud-Atmosphere-Land cal belt, and is home to the largest subtropical stratocumu- Study Regional Experiment (VOCALS-REx) was an interna- lus deck on Earth. The ﬁeld intensive phase of VOCALS- tional ﬁeld program designed to make observations of poorly REx took place during October and November 2008 and understood but critical components of the coupled climate constitutes a critical part of a broader CLIVAR program system of the southeast Paciﬁc. This region is characterized (VOCALS) designed to develop and promote scientiﬁc ac- by strong coastal upwelling, the coolest SSTs in the tropi- tivities leading to improved understanding, model simula- tions, and predictions of the southeastern Paciﬁc (SEP) cou- pled ocean-atmosphere-land system, on diurnal to interan- nual timescales. The other major components of VOCALS Correspondence to: R. Wood are a modeling program with a model hierarchy ranging from ([email protected]) the local to global scales, and a suite of extended observa- Variability of the American Monsoon Systems, an international tions from regular research cruises, instrumented moorings, CLIVAR program. Published by Copernicus Publications on behalf of the European Geosciences Union. 100 W U S S F UR 628 R. Wood et al.: VOCALS operations and satellites. The two central themes of VOCALS-REx fo- The Southeast Pacific Climate System cus upon (a) links between aerosols, clouds and precipitation and their impacts on marine stratocumulus radiative proper- ties, and (b) physical and chemical couplings between the up- per ocean and the lower atmosphere, including the role that mesoscale ocean eddies play. A set of hypotheses designed aerosol to be tested with the combined ﬁeld, monitoring and model- transport ing work in VOCALS is presented here. A further goal of copper smelters, VOCALS-REx is to provide datasets for the evaluation and urban pollution improvement of large-scale numerical models. VOCALS- cold water transport REx involved ﬁve research aircraft, two ships and two sur- face sites in northern Chile. We describe the instrument pay- loads and key mission strategies for these platforms and give a summary of the missions conducted. 1 Introduction Fig. 1. Key features of the southeast Paciﬁc (SEP) coupled climate 1.1 Scientiﬁc motivation system being explored in the VOCALS Program. Interactions between the South American continent and the Southeast Paciﬁc (SEP) Ocean are extremely important for et al., 1996). The representation of stratocumulus in large both the regional and global climate system. Figure 1 in- scale models over the SEP is improving in some global mod- els, but most models continue to have large biases in the lo- dicates some of the key features associated with these in- cation and albedo of cloud and the boundary layer vertical teractions. The great height and continuity of the Andes structure (Bretherton et al., 2004; Wyant et al., 2010). Ob- Cordillera forms a sharp barrier to zonal ﬂow, resulting in servations are highlighting the importance of drizzle precip- strong winds (coastal jet) parallel to the coasts of Chile and itation to SEP marine stratocumulus (e.g. Bretherton et al., Peru (Garreaud and Munoz ˜ , 2005). This, in turn, drives in- 2004; Caldwell et al., 2005; Comstock et al., 2005), and ob- tense oceanic upwelling along these coasts, bringing cold, servations and models point to a signiﬁcant role for drizzle in deep, nutrient/biota rich waters to the surface. As a result, affecting stratocumulus cloud cover and radiative properties, the coastal SEP sea-surface temperatures (SSTs) are colder in particular in promoting transitions from closed to open along the Chilean and Peruvian coasts than at any compa- mesoscale cellular convection (e.g. Comstock et al., 2007; rable latitude elsewhere. The cold surface, in combination Savic-Jovcic and Stevens, 2008; Wang and Feingold, 2009; with warm, dry air aloft, is ideal for the formation of ma- rine stratocumulus clouds, and supports the largest and most Wang et al., 2010) and the formation of so-called “pockets of persistent subtropical stratocumulus deck in the world (Klein open cells” (POCs) (Bretherton et al., 2004; Stevens et al., and Hartmann, 1993). The presence of this cloud deck has 2005). Physical parameterizations currently used in large a major impact upon the Earth’s radiation budget by reﬂect- scale models do not yet attempt to represent mesoscale in- ing solar radiation. This helps maintain cool SSTs, result- teractions between precipitation and cloud cover. ing in tight couplings between the upper ocean and lower There is evidence that precipitation in marine stratocumu- atmosphere in this region. The unique climate of the SEP lus may be inﬂuenced by anthropogenic aerosols (e.g. Geof- has been very sparsely observed, yet has great economic im- froy et al., 2008; Brenguier and Wood, 2009), which suggests pact, with ﬁshing in the Humboldt Current system represent- a potential role for aerosols to inﬂuence cloud macrostructure ing 18–20% of the worldwide marine ﬁsh catch (source: UN in addition to their microphysics. Aerosol indirect effects on LME report). warm clouds remain poorly treated in large scale numerical It is a challenge for global and regional models to success- models (e.g. Lohmann and Feichter, 2005), chieﬂy because fully simulate the SE Paciﬁc climate system, because of its the overall impact of aerosols on cloud radiative properties sharp horizontal and vertical gradients and the importance depends upon numerous complex small scale and mesoscale of subgridscale and poorly resolve physical processes. Most dynamical responses which result in macrophysical cloud coupled GCMs obtain SSTs that are too warm and have too changes (Stevens and Feingold, 2009). Satellite and research few clouds over the SEP, and show unrealistic features in the cruise data show strong gradients in aerosol and cloud mi- simulation of the warm tropics downstream (deSzoeke and crophysical properties between the near-coastal and more re- Xie, 2008). There are major uncertainties in the representa- mote marine region of the SEP (Wood et al., 2008), making tion of key physical processes in these models, which may this a region where the Twomey effect may be particularly be contributing to these errors (e.g. Mechoso et al., 1995; Ma strong (see e.g. George and Wood, 2010). Since this is also Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ 40 S Warm SST R. Wood et al.: VOCALS operations 629 a region where clouds are prone to drizzle (Bretherton et al., Studies of the upper ocean heat budget offshore of the 2004; Leon et al., 2008), it is also a region potentially well- coastal upwelling zone indicate weak mean advection, ener- suited to the study of aerosol-cloud interactions. getic eddies, and the need for a source of relatively cold, fresh In the SEP region there are important contributions to the water (Colbo and Weller, 2007). This divergence of heat and atmospheric aerosol from both natural and anthropogenic salt is presumably achieved by the interaction of mesoscale sources (Tomlinson et al., 2007; Hawkins et al., 2010). Cloud and submesoscale processes with the surface layer, though droplet effective radii are small off the coast of Northern the precise mechanisms are presently unclear. Candidates in- Chile, implying elevated concentrations of cloud droplets clude oceanic eddies advecting relatively cold, fresh anoma- (Wood et al., 2008; George and Wood, 2010; Painemal and lies westward from the coastal zone and vertical mixing pro- Zuidema, 2010). These elevated concentrations are broadly cesses transporting heat and salt downward, across the base downwind of major copper smelters whose combined sulfur of the oceanic mixed layer. In general, however, little is know −1 emissions total approximately 1 TgS yr , comparable to the about the oceanic eddy processes in the SEP, not only re- entire sulfur emissions from large industrialized nations such garding their role in inﬂuencing the mixed layer properties as Mexico and Germany. Offshore transport events have been but also their potential role in modulating the concentration shown to lead to elevated droplet concentrations offshore of aerosol precursors such as dimethylsulﬁde and complex (Huneeus et al., 2006). However, little is actually known organic species. about the aerosol composition in the region since there have Clouds over the SEP exhibit a much stronger diurnal cycle been very few measurements. We do not yet know the ex- of cloud cover and liquid water path, LWP (Rozendaal et al., tent of the anthropogenic inﬂuence, nor do we fully under- 1995; Wood et al., 2002) than MBL clouds at comparable lat- stand the complex chemistry occurring in the pristine bound- itudes in the Northern Hemisphere. Regional model simula- ary layer further offshore. tions (Garreaud and Munoz ˜ , 2004) suggest that a large-scale In the absence of cloud macrophysical responses, the re- diurnal subsidence wave formed by the interaction of the duced droplet effective radii resulting from increased con- coastal jet along the Chilean coast with dry convective heat- centrations of cloud droplets would increase the reﬂected so- ing over the western Andean slopes travels at least 1000 km lar radiation, and estimates of the component of the reﬂected over the SEP and leads to a strong diurnal cycle of subsidence shortwave radiation due to geographic variability in effective at remote locations. Using improved observations of how this −2 radius alone are ∼10–20 W m or 20–40% of the mean re- wave inﬂuences the diurnal cycle of marine stratocumulus ﬂected shortwave (George and Wood, 2010). The magnitude should be useful for assessing whether the diurnal variations of these estimates is such that the indirect effects of aerosols of clouds in large scale models are well represented. on clouds could lead to signiﬁcant decreases in the amount 1.2 Motivation for the VOCALS regional experiment of solar radiation entering the ocean, with signiﬁcant impli- cations for the ocean heat budget. However, we do not yet The science issues described above are central to VOCALS fully understand the controls on cloud droplet concentration (VAMOS Ocean-Cloud-Atmosphere-Land Study), an inter- in the MBL, and it is possible that meteorological controls national CLIVAR program to develop and promote scientiﬁc (e.g. precipitation sinks) in addition to aerosol sources may activities leading to improved understanding, model simula- play a signiﬁcant role. Further, we are beginning to under- tions, and predictions of the southeastern Paciﬁc (SEP) cou- stand that cloud responses to aerosols are not solely due to pled ocean-atmosphere-land system, on diurnal to interan- the Twomey effect alone, and that fast feedbacks can both nual timescales. VOCALS is ultimately driven by a need enhance and counteract the Twomey effect (e.g. Ackerman for improved numerical model simulations of the coupled et al., 2004; Xue et al., 2008). climate system in both the SEP and over the wider tropics Early estimates of surface heat ﬂuxes from climatologies and subtropics. At the root of VOCALS’s approach to the and numerical weather prediction models showed diverse problem is the premise that its solution requires a synergy conclusions as to whether or not the offshore ocean gained between numerical modeling, ﬁeld studies, and extended ob- from or lost heat to the atmosphere. Observations from de- servations such as buoys and satellites. With this in mind, the ployment of the IMET surface mooring beginning in 2000 VOCALS Regional Experiment (VOCALS-REx) was con- near the location of the annual maximum in stratus cloud −2 ceived. In this manuscript we present an overview of the cover showed that the ocean gains about 40 W m annu- hypotheses, instrumentation, sampling platforms, sampling ally and was subject to over 1 m in evaporation (Colbo and strategies, and missions conducted in pursuit of the science Weller, 2007; deSzoeke et al., 2010). This surface forcing goals. We deliberately do not discuss any scientiﬁc results was applied to a relatively thin ocean surface mixed layer from REx; this paper is intended as a background framework (annual maximum thickness of about 150 m) that lies over a and a supplement to the numerous other papers which present relatively cold, fresh water mass formed to the south. For those results. oceanographers, the challenge is to understand how the shal- low ocean surface layer under the clouds maintains its tem- perature and salinity under this surface forcing. www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 630 R. Wood et al.: VOCALS operations Table 1. The VOCALS Hypotheses. 1. AEROSOL-CLOUD-DRIZZLE HYPOTHESES Variability in the physicochemical properties of aerosols has a measurable impact upon the formation of drizzle in H1a stratocumulus clouds over the SEP. Precipitation is a necessary condition for the formation and maintenance of pockets of open cells (POCs) within H1b stratocumulus clouds. The small effective radii measured from space in the coastal region of over the SEP are primarily controlled by an- H1c thropogenic, rather than natural, aerosol production, and entrainment of polluted air from the lower free-troposphere is an important source of cloud condensation nuclei (CCN). H1d Depletion of aerosols by coalescence scavenging is necessary for the maintenance of POCs. 2. COUPLED OCEAN-ATMOSPHERE HYPOTHESES Improvement of CGCMs performance in the SEP is key to the successful simulation of the ITCZ/SPCZ, complex, which will also beneﬁt simulation of other regions. A signiﬁcant improvement can be achieved through better H2a representing the effects of stratocumulus clouds on the underlying surface ﬂuxes and those of oceanic mesoscale eddies in the transport of heat. Oceanic mesoscale eddies play a major role in the transport of relatively fresh water from the coastal upwelling region and in the production of sea-water and atmospheric DMS in the coastal and offshore regions. Upwelling, by H2b changing the physical and chemical properties of the upper ocean, has a systematic and noticeable effect on aerosol precursor gases and the aerosol size distribution in the MBL over the SEP. The diurnal subsidence wave (“upsidence wave”) originating in northern Chile/southern Peru has an impact upon H2c the diurnal cycle of clouds that is well-represented in numerical models. The entrainment of relatively cool fresh intermediate water from below the surface layer during mixing associated H2d with energetic near-inertial oscillations generated by transients in the magnitude of the trade winds is an important process to maintain heat and salt balance of the surface layer of the ocean in the SEP. In Sect. 6, we will brieﬂy summarize the VOCALS strat- 2 VOCALS-REx study region and dates egy for coordinating modeling work with REx (again, with- VOCALS-REx took place during October and November out presenting results). REx was designed to inform im- 2008, engaging over 150 scientists from 40 institutions in provement of both global and regional climate and chemi- 8 nations. A variety of operations within a limited domain cal transport models and also process-level models such as of the SEP coupled climate system were conducted (Fig. 2). large-eddy simulations of aerosol-cloud interaction. In addi- REx operations took place in the domain 69–86 W, 12– tion, REx made use of real-time output from several models ◦ ◦ 31 S, with a concentration of sampling close to the 20 S for mission planning. latitude line. This parallel was chosen as it transects the VOCALS-REx provided intensive observations of key heart of the SEP stratocumulus sheet (Klein and Hartmann, processes contributing to the climate of the SEP. The obser- 1993; George and Wood, 2010), exhibits strong longitudinal vations are being used to help test a coordinated set of hy- microphysical contrasts (Bennartz, 2007; Wood et al., 2008; potheses presented in Table 1, to evaluate our ability to model George and Wood, 2010; Bretherton et al., 2010), crosses the important physical and chemical processes in the SEP, a region where open cell formation is frequently observed and to help evaluate the performance of satellite retrievals. (Wood et al., 2008), and is impacted by mesoscale ocean ed- The VOCALS-REx hypotheses are organized into two broad dies (e.g. Colbo and Weller, 2007; Toniazzo et al., 2009). themes: (1) the impacts of aerosols upon the microphysical Overall, the VOCALS-REx period was characterized and structural properties of stratocumulus clouds and drizzle by near climatological atmospheric conditions off northern production; (2) the coupled ocean-atmosphere-land system. Chile and southern Peru (Toniazzo et al., 2011). However, signiﬁcant variations in MBL depth occurred during October when midlatitude troughs reached the VOCALS region lead- ing to four episodes (1–2 day long) of mid-tropospheric up- ward motion. In contrast, November exhibited less synoptic Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ 1 km 4 km R. Wood et al.: VOCALS operations 631 craft measurements are designed to critically address several VOCALS-REx OPERATIONS S OUTH of the VOCALS hypotheses (Table 1), particularly those re- A MERIC A lated to aerosol-cloud-drizzle interactions and those involv- ing the sources and sinks of atmospheric aerosols. José Olaya Glider 15 S section POC missions 3.1.1 NSF/NCAR Lockheed C-130 and lagrangian Process Arica studies RHB Leg 1 The NSF/NCAR C-130Q is operated by the Research Avi- IB 20 S surveys DB + Iquique ation Facility (RAF) at the National Center for Atmo- Point oint . . . . . . . . . . . . . . . . Eddy transects RHB Leg 2 Eddy survey Alpha spheric Research (NCAR) in the United States. During REx the C-130 ﬂew missions up to 9 h in duration reach- Paposo ing 1600 km offshore, making it the longest range aircraft used in REx. The C-130 has a large payload and car- 500 km ries instruments and sensors in pods and pylons on both Pollution survey missions wings. Details of the instrumentation payload on the C- aircraft 130 are given in Table 2. The aircraft is ﬂown at an air- 30 S ship −1 speed of approximately 100 m s for boundary layer sam- IB: IMET Buoy pling. Details of the missions ﬂown in REx are given DB: DART Buoy Santiago PACIFIC OCEAN in Table 6. Further information on the instrumentation o o 85W80 75 70 W on the C-130 including data quality can be found on- line at http://www.eol.ucar.edu/about/our-organization/raf/ Fig. 2. VOCALS REx study region showing main sampling plat- data/vocals/vocals-documentation-summary. forms and mission types. The land aerosol/meteorology site at Pa- poso, the sounding station at Iquique, and the instrumented IMET 3.1.2 FAAM BAe-146 and DART buoys are also shown. The Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft is operated by a joint agreement forcing and almost continuous subsidence (Rahn and Gar- between the Met Ofﬁce and the Natural Environment Re- reaud, 2010b; Toniazzo et al., 2011). search Council (NERC) in the United Kingdom. The BAe- In the following sections we ﬁrst discuss the research plat- 146 served as the medium range aircraft operated in REx, forms and the instrumentation used to make observations ﬂying missions of typically 5 hours and sampling up to during VOCALS-REx, followed by the chief mission types 900 km offshore. The BAe-146 has a large payload and and sampling strategy. carries instruments and sensors in pods and pylons on both wings. Details of the instrumentation payload on the BAe- 146 are given in Table 2. The aircraft is ﬂown at an air- 3 Platforms and instrumentation −1 speed of approximately 100 m s for boundary layer sam- pling. Details of the missions ﬂown in REx are given in A total of ﬁve aircraft (NSF/NCAR C-130, the DoE G-1, the Table 7. Further information on the instrumentation on the CIRPAS Twin Otter, the FAAM BAe-146, and the NERC BAe-146 including data quality can be found online at http: Dornier 228, see Table 2) two research vessels (the NOAA //data.cas.manchester.ac.uk/vocals/vocals-uk-summary.pdf. R/V Ronald H. Brown, RHB, and the Peruvian IMARPE Jose ´ Olaya, see Tables 3 and 4 respectively) sampled the 3.1.3 DoE Gulfstream-1 (G-1) lower atmosphere and upper-ocean during REx. These mo- bile platforms were complemented by a number of ground- The Department of Energy Gulfstream-1 (G-1) is operated by based observational sites (Table 5). the Research Aircraft Facility (RAF) at the Paciﬁc Northwest National Laboratory in the United States. The G-1 served as 3.1 Aircraft platforms a medium range aircraft in REx, with sampling out to 800 km from the coast. The aircraft is ﬂown at an airspeed of approx- Three of the aircraft deployed in VOCALS-REx (C-130, −1 imately 100 m s for boundary layer sampling. Details of G-1 and Twin Otter) were operational from 14 October to the instrumentation payload on the G-1 are given in Table 2. 15 November 2008, with the other two aircraft (BAe-146 and Details of the missions ﬂown in REx are given in Table 8. Do-228) operational from 26 October–15 November 2008. Table 2 shows the dates over which missions were ﬂown, and The NERC Dornier-228 is operated by the Airborne Re- Fig. 3 provides a graphical representation of the aircraft sam- search and Survey Facility (ARSF) of the Natural Environ- pling as a function of day and longitude. Tables describing ment Research Council (NERC) in the United Kingdom. Its the speciﬁc aircraft missions are discussed below. The air- main role in VOCALS-REx was remote sensing of clouds out www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 632 R. Wood et al.: VOCALS operations Table 2. Details of the aircraft used in VOCALS-REx. Aircraft Location Dates Measurements Lockheed Arica Oct 15– Atmospheric state: thermodynamics; winds/turbulence; cloud water (King, PVM); cloud and C-130 Nov 15 drizzle microphysics (CDP, 2D-C). Remote sensing: radar reﬂectivity and dopper winds (University of Wyoming Cloud Radar, 95 GHz,nadir/zenith/45 down); cloud base/aerosol scattering (Wyoming Cloud Lidar, zenith); liquid/vapor water path (G-Band Vapor Radiometer, 183 GHz, zenith); broad-band irradiances (nadir and zenith, SW and LW). Aerosols: size distributions from 20 nm to 3 μm (heated/unheated); total CN; refractory CN; ultraﬁne CN; aerosol composition (aerosol mass spectrometer, SP2, single particle analysis); scattering and absorption; CCN spectrum (Static Diffusion (0.1%< S < 1.5%) ; cloud water composition (major anions and cations, formaldehyde, peroxides, soluble Fe and Mn, organic acids, S(IV), total organic carbon). Trace gases: CO; O ; SO /DMS (quadrupole mass spectrometry). 3 2 BAe-146 Arica Oct 26– Atmospheric state: thermodynamics; winds/turbulence; dropsondes (Vaisala RD93 Revision Nov 13 F); cloud water (Johnson-Williams and Nevzorov); cloud and drizzle microphysics (CDP, CIP, FSSP, 2D-C, CAPS). Remote sensing: spectrally-resolved hemispheric shortwave irradiances (SHIMS); hyperspectral IR radiance (ARIES); SW broad-band irradiances. IR upwelling brightness temperature (Heimann), liquid/water vapor path (89–183 GHz, MARSS, scanning). Aerosols: size distributions from 50 nm to 3 μm; total CN; aerosol composition (aerosol mass spectrometer, impactors, single particle analysis); scattering and absorption; wet nephelometer (RH-scanning); CCN (variable supersaturations); volatility. Trace gases: CO, O , NO , PAN, SO (Teco, low sensitivity). 3 x 2 Gulfstream-1 Arica Oct 14– Atmospheric state: temperature, humidity, winds/turbulence/turbulence dissipation, cloud (G-1) Nov 13 and drizzle microphysics (FSSP at 200 Hz, CAPS probe in particle-by-particle mode) Remote sensing: UV zenith/nadir Aerosols: size distributions from 16–3000 nm (TSEMS, FIMS, PCASP), total CN (> 10 nm and > 2.5 nm), CCN (3 supersaturations, 0.18%, 0.26%, and 0.35%), aerosol composition (aerosol mass spectrometer, particle into liquid sampler, TRAC), scattering and absorption (3-wavelength nephelometer, 3-wavelength PSAP, Photo-thermal interferometer, Single particle soot photometer) Trace gases: O (UV absorbance), O (5 Hz), CO (VUV-Fluorescence), SO (TEI, high 3 3 2 sensitivity), organics (PTRMS). Dornier-228 Arica Oct 26– Atmospheric state: temperature, humidity, winds/turbulence, cloud microphysics (FSSP) (Do-228) Nov 14 Remote sensing: Visible/near IR hyperspectral imagery (Specim AISA Eagle and Hawk); aerosol backscattering and cloud top height (Leosphere lidar, 355 nm, nadir); full-Stokes polarimeter (AMSSP); Aerosols: size distributions from 0.2–30 μm. Twin Otter Iquique Oct 16– Atmospheric state: thermodynamics; winds/turbulence; cloud water; cloud and drizzle Nov 13 microphysics (CDP, 2D-C). Remote sensing: radar reﬂectivity and Doppler winds (ProSensing 95 GHz FMCW radar pointing horizontally from starboard wing); nadir/zenith brightness temperature (Heimann). Aerosols: size distributions from 20 nm to 3 μm (heated); total CN; ultraﬁne CN; CCN (2 supersaturations, 0.2 and 0.4%). See map, Fig. 2. Operated by the National Center for Atmospheric Research and funded by the US National Science Foundation. Operated by the Facility for Airborne Atmospheric Measurements (FAAM), funded jointly by The Met Ofﬁce and the Natural Environment Research Council in the UK. Operated by the Research Aircraft Facility at the Paciﬁc Northwest National Laboratory and supported by the US Department of Energy (DoE). Operated by the Airborne Remote Sensing facility of the Natural Environment Research Council, UK. Operated by the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) and supported by the US Ofﬁce of Naval Research (ONR). to 76 W, using lidar, a hyperspectral imager and polarime- given in Table 9. Most ﬂights took place at an altitude of ter. Details of the instrumentation payload on the Do-228 are 4–5 km, with the remainder proﬁling the free troposphere to given in Table 2. Details of the missions ﬂown in REx are measure in-situ aerosol concentration. Typically, the Dornier Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ R. Wood et al.: VOCALS operations 633 Table 3. Details of the Ronald H. Brown (RHB) measurements in VOCALS-REx. Location /Dates Measurements Atmospheric state: temperature, humidity, winds (ﬂux tower), cloud observations and photography R/V Ronald H. Brown Upper air: 6×daily radiosonde (Vaisala RS92) launches. See map Fig. 9 Oct 25 –Dec 2 Remote sensing: C-band radar reﬂectivity and Doppler winds within drizzle (3-d volumetric and range-height scans every 3 min, 60 km range); W-band radar reﬂectivity proﬁles and Doppler velocity for cloud/drizzle (vertically pointing 95 GHz cloud radar); cloud base and drizzle backscatter (lidar ceilometer); volumetric lidar backscatter and winds (scanning High Resolution Doppler Lidar, also operated in vertically pointing mode, 6 km range); liquid water path and water vapor path (23/31/90/183 GHz microwave radiometers); broad band irradiances. Aerosols: size distributions from 20 nm to 10 μm diameter; CN (> 12nm); ultraﬁne CN (> 3nm), aerosol mass and composition (Aerosol Mass Spectroscopy 80–800 nm, super- and sub-micron impactors for ion and gravimetric mass analysis, 7-stage impactor for ion composition, single particle analysis, submicron FTIR for organic functional groups and mass, single particle STXM-NEXAFS and SEM-EDX analysis); super- and sub-micron scattering and absorption coefﬁcients at three visible wavelengths; CCN spectrum (5 supersaturations, 0.1 0.15, 0.2, and 0.3, and 0.6%); aerosol volatility at 230 C for 20–800 nm size interval; aerosol proﬁling (differential absorption spectroscopy, MAX-DOAS) Trace gases: Radon ( Rn); O ; atmospheric DMS (quadrupole mass spectrometry); seawater DMS/DMSP, chlorophyll-a, and dissolved CO ; reactive trace gases (differential absorption spectroscopy, MAX-DOAS) Oceanography: 438 Underway CTD proﬁles (temperature, conductivity, pressure) to between 200 and 800 m depth, horizontal spacing from 1–30 km; 35 CTD proﬁles to 2500 m in and outside of eddies/fronts with associated water sampling for the collection of nutrients, salinity and oxygen samples; 10 SOLO proﬁling ﬂoats deployed with dissolved oxygen sensors; underway sea-surface salinity/temperature measurements; 19 surface drifters; 15 Vertical microstructure proﬁles (high resolution temperature, conductivity, velocity, pressure). See map, Fig. 2. Operated and funded by the US National Oceanographic and Atmospheric Administration (NOAA), with additional support for shipborne sampling from the National Science Foundation. overﬂew the ﬂight path of the FAAM BAe146 with a similar 17 October 2008. Figure 3 provides a graphical represen- −1 airspeed (∼ 100 m s ) and/or C-130 especially during the tation of the ship sampling as a function of day and longi- 20 S missions (see below). tude. Figures describing the speciﬁc ship sampling strategies are disussed below. The ship measurements are designed to 3.1.4 CIRPAS Twin Otter critically address several of the VOCALS hypotheses (Ta- ble 1), particularly those related to the upper ocean, aerosol- The Twin Otter operated by the Center for Interdisciplinary cloud-drizzle interactions, the physical and chemical inter- Remotely Piloted Aircraft Studies (CIRPAS) was instru- actions between the upper ocean and the lower atmosphere, mented to make turbulence, cloud microphysics, and aerosol and those involving the sources and sinks of atmospheric measurements (Table 2) in the near coastal region of the VO- aerosols. ◦ ◦ CALS domain at 20 S, 72 W (a location termed here as Point Alpha, see Fig. 2). This relatively slow-moving air- 3.2.1 NOAA R/V Ronald H. Brown −1 craft (∼60 m s ) made 5 h ﬂights originating from Iquique Chile that allowed for 3 h of sampling at Point Alpha on 18 The R/V Ronald H. Brown is operated by the National ﬂights (Table 10). Oceanographic and Atmospheric Administration (NOAA), and served as the primary shipborne sampling platform for 3.2 Ship platforms measurements in the vicinity of 20 S from the coast out The two ships in VOCALS-REx sampled different locations to 85 W. The RHB also provided the means to deploy and at different times. The R/V Ronald H. Brown was opera- recover moorings, drifters, and proﬁling ﬂoats during VO- tional for two phases, the ﬁrst from 25 October to 2 Novem- CALS REx. The RHB payload was designed to sample both ber 2008 and the second from 10 November to 2 Decem- the upper ocean and the lower atmosphere during REx, and ber 2008. The Peruvian R/V Jose ´ Olaya operated from 2– details are given in Table 3. The multi-week RHB cruises www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 634 R. Wood et al.: VOCALS operations Longitude [ W] 85 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 Campaign Day 1 1 C-130 (1st Oct = 1) 2 G-1 BAe-146 4 4 5 Do-228 Twin Otter 7 7 RHB José Olaya 10 [12-17 S] 10 Iquique 13 13 and Paposo land sites 16 16 19 19 IMET Buoy 22 22 25 25 26 26 28 28 29 29 31 31 1 32 32 1 Day in Nov 2 33 2 3 34 34 3 4 35 35 4 5 36 5 6 37 37 6 7 38 38 7 8 39 8 9 40 40 9 10 41 41 10 11 42 11 12 43 43 12 13 44 44 13 14 45 14 15 46 46 15 16 47 47 16 85 84 83 82 81 80 79 78 77 76 75 74 73 72 71 17 48 17 18 49 49 18 19 50 50 19 20 51 20 21 52 52 21 22 53 53 22 23 54 23 24 55 55 24 25 56 56 25 26 57 26 27 58 58 27 28 59 59 28 29 60 29 30 61 61 30 62 62 85 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 Longitude [ W] Fig. 3. Operations summary showing platform longitude against time during VOCALS-REx. with 6 daily upper air soundings and continuous measure- 3.2.2 Peruvian R/V Jose ´ Olaya ments by most sensors are able to capture details of the MBL diurnal variations and aerosol-cloud-drizzle evolution in a The Jose ´ Olaya is surveyed by the Instituto del Mar del Peru ´ way that the aircraft platforms cannot. The paper by de (IMARPE) and operated in Peruvian near-coastal waters to Szoeke et al. (2010) documents meteorology, surface ﬂux, provide extensive sampling of the upper ocean, with addi- and cloud remote sensing measurements from the RHB. tional atmospheric measurements (Table 4). The sampling Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ R. Wood et al.: VOCALS operations 635 Table 4. Details of the R/V Jose ´ Olaya Balandra measurements in VOCALS-REx. Location /Dates Measurements Atmospheric state: temperature, humidity, winds, cloud observations, photography. R/V Jose ´ Olaya Balandra Upper air: regular radiosonde launches predominately within an area about 200 km off the Pisco-San Juan See map Fig. 8 region (see Fig. 8). Oct 2-17 Oceanography: 113 CTD proﬁles (temperature, conductivity, pressure) to 1000 m depth in the coastal upwelling off southern Peru extending from the coast to 80–320 km, horizontal spacing from 19 km (nearshore) to 32–45 km (offshore). The CTD was deployed with dissolved oxygen and ﬂuorescence sensors. Continuous records of VM-ADCP data (bin size 8 m, ping rate 0.3 s-1); underway sea surface temperature/salinity; 8 surface drifters. Collection of water samples for determination of oxygen, nutrients (phosphate, silicate, nitrate, nitrite), ph and chlorophyll-a concentrations in 78 stations. Underway measurements of partial pressure of carbon dioxide (pCO ) complemented the biogeochemical observations. Glider mission: continuous physical and biogeochemical data (temperature, salinity, dissolved oxygen, ﬂuorescence and turbidity) were collected by a repeating section between 10 km and 100 km from the coast off Pisco. Observations every 24 s, 5 m along the vertical over the upper 200 m depth started in 3 October to 14 November 2008. Biology: 37 Standard and 35 WP-2 net sampling for phytoplankton and zooplankton qualitative analysis, respectively; 17 Hensen net samples for zooplankton vertical distribution; 153 samples at depths 0–75 m (Niskin bottles) for phytoplankton quantitative analysis); 313 samples collected underway at 20 min interval with the Continuous Underway Fish Egg Sampler (CUFES). Fishery hydroacoustics: continuous records of echosounder EK60 at frequencies 38, 120 and 200 kHz to document ﬁsh (in particular anchovy) abundance and patterns of distributions for the upper 500 m on the vertical. Data averaged each 1 Basic Sample Unit (1 nm) horizontally. See map, Fig. 2. Operated and funded by the Instituto del Mar del Peru ´ (IMARPE), with additional support for upper air measurements and ship mobility from the National Science Foundation, Institut de Recherche pour le Dev ´ eloppement and Institut National des Sciences de l’Univers for the glider mission. strategy (see below) was designed to examine the coastal up- 3.3 Fixed location sites welling region off Pisco-San Juan and extended from the Pe- ruvian coast to 100–300 km offshore. The upper and lower 3.3.1 Paposo atmosphere, the upper ocean property distribution and circu- lation, the biogeochemical characteristics, the plankton com- Extensive aerosol and meteorological measurements were munity structure as well as ﬁshery responses were measured ◦ 0 ◦ 0 made at two sites near Paposo (25 01 S, 70 28 W) on the in a comprehensive, multidisciplinary basis. Details on the Northern Chilean coast (see map Figs. 2 and 4). In terms of instrumentation onboard the Olaya are provided in Table 4. the ﬂow in the MBL, Paposo sits upwind of the primary fo- The National Center for Atmospheric Research (NCAR) cus area along the 20 S parallel and the measurements are Earth Observing Laboratory (EOL) deployed a GAUS (GPS designed to help constrain the physical and aerosol proper- Advanced Upper-air Sounding systems) radiosonde station ties of airmasses leaving the continent to be advected over on the Jose ´ Olaya during VOCALS with sondes launched by the broader SE Paciﬁc region. Two sites were used near IMARPE and IGP (Instituto Geof´ ısico del Peru) ´ and IRD (In- Paposo (Table 5) on the Northern Chilean coast. In-situ stitut pour le Recherche ´ et Developpement) ´ scientists. A to- aerosol physical and chemical measurements, and meteoro- tal of 133 soundings were launched at varying intervals from logical sampling, were conducted at an elevated (upper) site 30 September to 17 October 2008. The launch sites were ◦ 0 00 ◦ 0 00 (25 00 22.55 S, 70 27 02.01 W, 690 m a.s.l.) in the coastal predominately within an area about 200 km off the coast of range immediately adjacent to the ocean (1.7 km east of the the Ica region of southern Peru. Vaisala RS92G radiosondes shore). Lidar proﬁles and soundings were made from a lower were used throughout. ◦ 0 00 site near sea-level in the village of Paposo (25 00 34.41 S, ◦ 0 00 70 27 53.64 W, 20 m a.s.l.) situated 100 m from the shore and 1.5 km to the WSW of the elevated site. The elevated Paposo site is close to the peak of the hill in the coastal range in which it is situated (Fig. 4). www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 636 R. Wood et al.: VOCALS operations Table 5. Details of the surface sites used in VOCALS-REx. ◦ 0 Paposo (upper site) 25 00 S, Oct 15 Atmospheric state: temperature, humidity, winds, pressure (weather station), ◦ 0 70 27 W, –Nov 15 downwelling shortwave and net (LW+SW) radiation (July 23–Nov 15). 690 m (Jul 23 Aerosols: aerosol size distribution (20 nm–5 μm, SMPS/OPC); total CN (CPC, a.s.l. –Nov 15 Nov 4–15 only), aerosol composition (submicron impactors for ion and for met. gravimetric analysis); light scattering (Oct 27–Nov 15, Radiance Research and nephelometer, single wavelength); absorption (PSAP, Nov 4–15 only); black radiation) carbon (aethelometer, Nov 4–15 only); Cloud droplet residuals (Nov 4–18 only, Counterﬂow virtual impactor with instrumentation as at Paranal [see below] behind, plus liquid water content); Trace gases: O . ◦ 0 Paposo (lower site) 25 01 S, Oct 15 Atmospheric state: temperature, humidity, winds, pressure (weather station), ◦ 0 70 27 W, –Nov 15 downwelling shortwave and net (LW+SW) radiation (July 23–Nov 15). Upper 31 m air: multiple daily radiosonde launches (2×daily at 00/12 UTC, Oct 17–23; a.s.l. 3×daily at 00/12/21 UTC, Oct 24–Nov 9; 4×daily at 00/06/18/21 UTC, Nov 11–12; 5×daily at 00/06/12/18/21, Nov 13–15), Vaisala RS80-15G sondes Remote sensing: lidar backscatter from aerosols and clouds, polarized (mostly vertical pointing, but some slant path scans, 1.574 μm wavelength, 1.5 m maximum vertical resolution, linear and circular polarizations) ◦ 0 Paranal 24 38 S, Oct 17 Aerosols: Aerosol total concentration (TSI 3010 CPC, >10 nm); Aerosol size ◦ 0 70 24 W, –Nov 4 distributions (DMPS 20–300 nm, unheated/heated to 50–400 C; OPC 2635 m 0.26–2.2 μm); Volatility TDMA (not continuous, only occasionally range a.s.l. 20–300 nm); Aerosol scattering (nephelometer) and light absorption (PSAP and Aethelometer); Samples for single particle analysis. ◦ 0 Iquique 20 16 S, Oct 15 Upper air: 6×daily radiosonde launches (00, 04, 08,...UTC) ◦ 0 70 08 W, –Nov 15 15 m a.s.l. ◦ 0 IMET Buoy 19 43 S, Entire Atmospheric state: Winds (propeller/vane), temperature, pressure, humidity ◦ 0 a 85 35 W period (capacitance), precipitation (tipping bucket); Radiation: downwelling longwave and shortwave irradiance. Oceanography: upper ocean temperature, salinity and currents, with depth sampling varying over time. ◦ 0 DART/SHOA Buoy 19 34 S, Oct 31 Atmospheric state: winds (propeller/vane), temperature, pressure (from 31 Oct ◦ 0 b 73 47 W –end 2008 only), humidity (capacitance, from 31 Oct 2008 only); Radiation: downwelling longwave and shortwave irradiance. Oceanography: temperature and salinity at 14 depths from 10–310 m The IMET buoy has been providing data nearly continuously since October 2000. Data are available from the VOCALS data archive. A detailed description of the meteorological instruments and their performance can be found in Colbo and Weller (2009). Oceanographic measurements are detailed at http://uop.whoi.edu. The DART/SHOA buoy was operational 31 October 2008–3 Jan 2010. Data are available from the VOCALS data archive. Meteorological measurements from an automatic weather (< 1 μm diameter) aerosols on ﬁlters for chemical analysis. station at the upper Paposo site were started on 24 July 2008 Aerosol ﬁlter measurements are described further in Chand and continued through the end of November 2008. During et al. (2010). Meteorological and radiation measurements the period of intensive REx sampling at Paposo (17 October– at the upper site were made by the University of Chile, and 15 November 2008), the upper site was almost continually these measurements are described further in (Munoz ˜ et al., within the marine boundary layer (MBL), although earlier 2011). in the season the inversion was occasionally lower which al- At the lower Paposo site, an eye-safe 1.574 μm lidar, a lowed sampling above the MBL. Table 5 details the measure- weather station, and a sounding system were installed at the ments made at the upper Paposo site. Aerosol sampling was Paposo foothill site near the coast (Table 5 and map Fig. 4). carried out using a custom-made multidirectional aerosol in- The lidar was primarily vertically-pointing but some slant let and a multiport sampling conﬁguration (see Fig. 4), with path scans were also performed. An identical set of mete- additional sampling lines for aerosols during 4–15 Novem- orological parameters to that measured at the upper site was ber. The primary sampling line was used to connect with the measured at the lower site. Multiple soundings per day were scanning mobility particle spectrometer (SMPS), optical par- made from the site (Table 5 provides details of the launch ticle counter (OPC), nephelometers, aethalometer and ozone times). analyzer, and the same line was used to sample submicron Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ R. Wood et al.: VOCALS operations 637 Table 6. Details of C-130 aircraft missions conducted in the VOCALS Regional Experiment. Flight Date Times [UTC] Mission/Location Notes T/O Land ◦ ◦ ◦ RF01 Oct 15 16:49 20:11 Partial 20 S to 20 S, 75 W Day mission, solid cloud deck RF02 Oct 18 13:04 21:27 20 S/POC Drift Day mission, solid cloud deck, polluted with little drizzle. POC sampling of rift-like feature RF03 Oct 21 06:02 14:22 20 S Night mission, solid cloud deck, signiﬁcant microphysical gradient; notably shallow MBL RF04 Oct 23 06:01 14:20 20 S Night mission, broken/open cells at far west RF05 Oct 25 06:32 15:25 20 S Overﬂight of RHB RF06 Oct 28 06:20 15:10 POC Drift Night mission, very clear POC edge sampled RF07 Oct 31 06:03 14:58 POC Drift/20 S Night mission, RF08 Nov 2 06:00 15:20 POC Drift Night mission, overﬂight of RHB RF09 Nov 4 06:02 14:54 POC Drift/20 S Night mission, POC sampling RF10 Nov 6 06:10 14:19 20 S Night mission, overcast with breaks and drizzling large mesoscale cells at west RF11 Nov 9 12:59 21:34 Pollution Survey to 30 S Day mission, Variable cloud morphology along coast, pollution plumes RF12 Nov 11 12:56 21:44 Pollution Survey to 30 S Day mission, Overcast cloud, overﬂight of RHB RF13 Nov 13 13:00 21:55 POC/20 S Day mission, Extensive clearing near coast, then thick cloud with POC RF14 Nov 15 13:00 22:00 POC Drift Day mission, rift/clearing sampled, high SO just above MBL at 80 W 3.3.2 Paranal term record of both the surface meteorology/radiation, and the upper ocean thermodynamic and dynamic structure. The A suite of aerosol measurements (see Table 5) in the free- meteorological and radiation measurements (Table 5) on the troposphere were also made for just under three weeks IMET buoy are described and their performance evaluated in (17 October to 4 November) at the high altitude Eu- Colbo and Weller (2009). The upper ocean measurements ◦ 0 00 ropean Southern Observatory at Paranal (24 37 39.00 S, include temperature proﬁles, sea-surface temperature, salin- ◦ 0 00 70 24 17.85 W, 2625 m a.s.l.), see map Fig. 4. ity and currents. Further details can be found on the WHOI Upper Ocean Processes website (Table 5). 3.3.3 Iquique 3.5 DART/SHOA Buoy The National Center for Atmospheric Research (NCAR) Earth Observing Laboratory (EOL) deployed a GAUS (GPS The Deep-ocean Assessment and Reporting of Advanced Upper-air Sounding systems) radiosonde station ´ ´ Tsunamis/Servicio Hidrograﬁco y Oceanograﬁco de la located in Iquique at the Universidad Arturo Prat Marine Sci- Armada de Chile (DART/SHOA) moored buoy at approxi- ◦ 0 00 ◦ 0 00 ◦ ◦ ences Campus (20 16 15 S, 70 07 52 W, 15 m a.s.l.). The mately 19.5 S, 74 W (see Table 5 for precise location) has stations was operated with the assistance of staff and students been instrumented with meteorological and oceanographic (see map Fig. 4). The launch site was on a steep slope, ap- measurements from October 2006 through January 2010. proximately 100 m inland and 20 m above the shoreline. A Meteorological measurements similar to those on the IMET total of 192 radiosondes were launched at 4 hourly intervals buoy (Colbo and Weller, 2009) were made during much of from 15 October to 15 November 2008. Weather conditions this period. Upper ocean measurements of temperature and at the site were generally clear and calm, with light sea (day- salinity at 14 depths were also made from 2006 onwards. time) and land (nighttime) breezes. Vaisala RS92G radioson- des were used throughout. 4 Sampling strategies 3.4 IMET Buoy 4.1 Matching sampling strategy to the VOCALS The Improved Meteorology (IMET) moored buoy is situated hypotheses ◦ ◦ at approximately 20 S, 85 W (see Table 5 for precise lo- cation) at the western end of the sampling conducted dur- The REx sampling strategy was carefully designed and coor- ing VOCALS-REx. The mooring has been operational since dinated between platforms to test key VOCALS hypotheses October 2000 and has provided an excellent intermediate- listed in Table 1. Approximately half way through the ﬁeld www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 638 R. Wood et al.: VOCALS operations Table 7. Details of BAe-146 aircraft missions conducted in the VOCALS Regional Experiment. Flight Date Times [UTC] Mission/Location Notes T/O Land ◦ ◦ B408 Oct 26 10:05 21:27 20 S XS Proﬁling up to 1500 m out to 79.5 W with saw-tooth proﬁle to 4800 m at west-most point. Reciprocal return. Increasing cloud base and tops with distance offshore B409 Oct 27 19:59 00:29 POC Drift Sampled open cellular (POC) region at ∼78 W at dusk. Very low CN in POC.C-130 sampled same advected airmass 12 h later B410 Oct 29 09:59 15:16 20 S XS Detour to rendezvous with DART buoy on outbound leg only. Proﬁling to 1600 m with deep proﬁle to 4600 m at west-most point. B411 Oct 30 10:25 15:48 RHB cosampling RHB on station near the DART Buoy. Cloud and MBL proﬁles en route. Several 20-min back and forth legs (parallel to mean wind) over RHB ◦ ◦ B412 Oct 31 09:47 14:52 20 S XS Proﬁling up to 1500 m out to 79.5 W. High level return with ◦ ◦ 7 dropsondes, every degree from 78 W to 72 W. B413 Nov 3 11:03 16:05 Ilo pollution survey Proﬁling from Arica to DART buoy to study coastal gradient in pollution, followed by coastal ﬂy-by aligned to mean wind direction to study potential pollution from the Ilo smelter. No evidence of fresh pollution due to smelter down-time. 4 dropsondes ◦ ◦ B414 Nov 4 09:44 15:04 20 S XS Proﬁling up to 1500 m out to 79.5 W. High level return with ◦ ◦ 7 dropsondes, every degree from 78 W to 72 W B415 Nov 5 09:12 14:33 POC Drift Sampled open cellular (POC) region at ∼78 W. Very low CN observed in POC. High-level return to base with 10 dropsondes released. B416 Nov 7 10:32 15:27 POC Drift Sampled open cellular (POC) region at ∼78 W. Very low CN observed in POC. High-level return to base with 11 dropsondes released (2 into POC) B417 Nov 9 09:58 21:34 20 S XS Proﬁling to 1600 m with deep proﬁle to 3200 m at west-most point. Reciprocal return. Transition in wind dynamics (coastal jet) observed at 75 W. B418a Nov 11 11:31 16:13 Coastal pollution Fly-by along coast (100 km offshore) in straight line from Arica to Survey south from Antofagasta, with MBL and cloud saw-tooth proﬁling. Refuel at Arica Antofagasta. B418b Nov 11 17:49 21:17 Return to Arica with legs directed offshore and parallel to mean wind to study land source Lagrangians. Several point sources noted. B419 Nov 12 11:29 16:51 RHB Cosampling Straight run from Arica to Ron Brown whilst on station near the DART Buoy performing cloud and MBL proﬁles en route. Several 20-min reciprocal legs (parallel to mean wind) performed, centred on Ron Brown, with cloud, MBL and deep proﬁles to 3.2 km ◦ ◦ B420 Nov 13 09:58 15:13 20 S XS/POC proﬁling up to 1500 m out to 81 W with a high level return and 10 sonde drops at 1 intervals. POC sampled brieﬂy at western point with 2 sondes dropped into cloud-clearing on return. phase, when the RHB was in between its two cruise legs, In the REx region, both repeated surveying and sampling an “all-hands” meeting was held in Arica to discuss progress of speciﬁc features are useful for testing these hypotheses. and strategize about the needs for sampling during the re- Repeated sampling of the persistent gradients in aerosols, mainder of the campaign. Some important adjustments to clouds and precipitation between nearshore and offshore the sampling strategy were made at this point. regimes allows robust features of the gradient region to stand out and can be used to study correlations among aerosols, Brieﬂy, the VOCALS aerosol-cloud-drizzle hypotheses cloud macrostructure, and meteorology present on individ- can be paraphrased as ual days. POCs present extreme examples (typically POCs – H1a: aerosol variations signiﬁcantly affect drizzle for- are among the very cleanest and most strongly drizzling of mation. airmasses in the SEP) that challenge our physical under- standing of cloud-aerosol-precipitation interaction. Thus, an – H1b/d: drizzle-induced aerosol scavenging is required aircraft sampling strategy mainly focused on repeated sam- for POC formation and maintenance. pling across the aerosol gradient region (with a few missions at the end parallel to the coast to characterize the offshore – H1c: cloud droplet radii are smaller near the coast due aerosol distribution upwind of the main VOCALS-REx study to anthropogenic aerosol emissions from South Amer- region), interspersed by opportunistic sampling of any POCs ica. Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ R. Wood et al.: VOCALS operations 639 km 5.0 Arica 4.5 Iquique Antofagasta 4.0 3.5 3.0 2.5 Paranal 2.0 1.5 Paposo 1.0 0.5 Santiago 0.0 (a) (b) o o o o o o 74 W 72 W 70 W 71 W 70 W 69 W Paposo sites View from upper site to SE (c) aerosol inlet weather station View from upper site to NNW aerosol inlet North 1 km Fig. 4. (a) Map showing location of ground sites used in VOCALS-REx, with (b) a zoomed in map for the red boxed area in (a). Panel (c) shows a Google Earth terrain image showing the Paposo sites looking approximately northward, together with photographs from the upper (elevated) Paposo site. within range. Because of the desire for repeated sampling – H2b/d: the offshore ocean mixed layer SST and salin- strategies, the aircraft favored particular times of day and ity are decreased by ocean mesoscale eddy transports did not attempt to characterize the diurnal variability of the and entrainment from below. Oceanic DMS affects the cloud-topped boundary layer. The ship, mooring, and land- boundary layer aerosol both in the upwelling zone and based sampling was aimed at complementing the aircraft far offshore. through a better characterization of diurnal variability along – H2c: a subsidence wave driven by slope heating on the 20 S (particularly with the RHB and the Iquique sounding Andes measurably affects the diurnal cycle of stratocu- site) and of the upstream anthropogenic aerosol sources (the mulus. Paposo and Paranal land sites). The observational VOCALS coupled ocean-atmosphere VOCALS-REx tackled these hypotheses mainly with a ship- hypotheses in Table 1 can be summarized: based strategy (RHB and Jose ´ Olaya), through sampling of clouds and atmospheric proﬁles through the diurnal cycle for H2c and survey-style sampling for H2b/d. www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 o o o o o 35 S 30 S 25 S 20 S 15 S o o o o 26 S 25 S 24 S 23 S -1 100 m s -1 100 m s -1 100 m s o -1 = 3.44 lon hr = 0.29 hr per lon -1 160 m s 640 R. Wood et al.: VOCALS operations C-130 OUTBOUND 85 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 o free troposphere 2 km C-130 Co-sampling with RHB 2 km MBL IMET Buoy R/V westernmost point o o Arica, Chile 20 S, 85 W o S.E. PACIFIC OCEAN Ronald H Brown o o [82-85 W] 18 S, 70 W OTHER A/C and C-130 RETURN Return leg 7-8 km BAe-146 free troposphere Do-228 2 km C-130 2 km MBL IMET Buoy R/V westernmost point o o Arica, Chile 20 S, 85 W o Ronald H Brown S.E. PACIFIC OCEAN o o [82-85 W] 18 S, 70 W 12pm along 20 S Aircraft altitude 8 11am > 6 km 4-6 km 7 10am < 4 km profile Do-228 6 9am C-130 8am BAe-146 4 7am 3 6am o o 1 longitude = 104.4 km at 20 S RHB +41 min Co-sampling 2 5am 4am Oct 19-24 Oct 28 - Nov 2 Nov 7-28 0 3am 85 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 Longitude [ W] Fig. 5. Cross Section mission ﬂight plan. Up to three aircraft (BAe-146, C-130, Do 228) were used in this mission, but in a number of cases ◦ ◦ ◦ only a single aircraft was used. In all cases, the aircraft ﬂew from Arica to 20 S, 72 W and then ﬂew westward along the 20 S parallel. The schematic shown here is for all three aircraft - the upper two panels show longitude-height diagrams while the lower panel shows a time- longitude plot color coded with altitude range. The C-130 ﬂew 60 km (10 min) straight and level legs near the surface (150 m altitude), in the cloud (typically 800–1300 m altitude) and above cloud (300 m above cloud top), interspersed with proﬁles up to 3000–4000 m. The C-130 ◦ ◦ typically reached 85 W. The BAe-146 ﬂew similar outbound legs, out to 79–80 W but then ﬂew the return leg at high altitude releasing dropsondes and making radiation measurements when working in concert with the C-130. When operating alone the BAe-146 repeated the in-situ sampling on the return leg. The Do-228, when employed in this mission, ﬂew legs at approximately 4000 m altitude using the nadir-viewing lidar and hyperspectral imagers to characterize clouds and aerosols below. There was a concerted effort for the three aircraft to sample the same location as closely in time as possible on the return leg (see bottom panel). For both sets of hypotheses, IMET/DART mooring obser- 4.2 Aircraft missions vations, satellite observations, and modeling on a range of The following aircraft mission strategies were used during scales are envisioned as vital complements to the in-situ ob- VOCALS-REx: servations. Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ -1 160 m s -1 100 m s ES ES Time after C-130 T/O [hr] Arica Approx. local time [assuming 3am C-130 T/O] R. Wood et al.: VOCALS operations 641 20 South Cross-Section Missions - All Platforms LONGITUDE West [on 20S] Mission Date Aircraft Mission# Times for 20S data 85 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 Time Time Time Key [local] [UTC] C-130 OUT RF02 13:04-16:09 3-4 6-7 Oct 18th C-130 RET No return 20S component RF02 N/A 5-6 8-9 7-8 10-11 C-130 OUT RF03 06:03-10:03 9-10 12-13 Oct 21st C-130 RET RF03 10:03-14:08 11-12 14-15 13-14 16-17 C-130 OUT RF04 05:53-09:50 15-16 18-19 Oct 23rd C-130 RET RF04 09:50-14:20 C-130 OUT R RF05 06:32-10:58 Oct 25th C-130 RET RF05 11:00-15:25 BAe-146 OUT R B408 10:05 - 12:50 Oct 26th BAe-146 RET B408 12:52 -15:05 BAe-146 OUT R B410 09:59 - 12:28 F Oct 29th BAe-146 RET B410 12:30 -15:16 C-130 OUT No outbound 20S component RF07 N/A BAe-146 OUT B412 09:47-12:59 Do-228 OUT VA04 11:30-13:39 Oct 31st C-130 RET RF07 12:16-14:58 BAe-146 RET B412 13:00 -14:52 Do-228 RET VA04 13:43-15:26 C-130 OUT No outbound 20S component RF09 N/A BAe-146 OUT B414 09:44 - 12:54 Do-228 OUT VA07 11:31-13:46 Nov 4th C-130 RET RF09 12:24-15:19 BAe-146 RET B414 12:55-15:04 Do-228 RET VA07 13:52-15:43 C-130 OUT RF10 06:10-10:09 Nov 6th C-130 RET RF10 10:09-14:19 BAe-146 OUT R B417 09:58-12:49 Do-228 OUT VA10 13:39-15:47 J Nov 9th BAe-146 RET B417 12:50-15:23 Do-228 RET VA10 15:51-17:52 C-130 OUT RF13 13:00-15:44 BAe-146 OUT B420 09:58-12:59 Do-228 OUT VA14 12:45-14:44 K Nov 13th C-130 RET No return 20S component RF13 N/A BAe-146 RET B420 13:00-15:13 Do-228 RET VA14 14:47-16:48 C-130 OUT RF14 13:00-15:48 L Nov 15th C-130 RET No return 20S component RF14 N/A Fig. 6. Cross Section missions summary as a function of date and longitude along 20 S. Color coding shows the approximate local/UTC time of sampling. Times for which Cross-Section mission data is available are provided at right. Individual aircraft ﬂight numbers are also given. Missions with missing outbound or return legs indicate that the aircraft was involved in a different mission for part of its ﬂight. 1. Cross-Section (XS) missions along 20 S latitude (or latitudes (especially by the G-1 aircraft, see Table 8). other proximal latitudes) from the coast to close to the Emphasis in these missions was on good sampling IMET buoy at 85 W (mission plan shown in Fig. 5) within the MBL and the air in the lowermost part of aimed to sample longitudinal gradients in clouds, the the free troposphere that would be entrained into the MBL, and aerosols. A total of 12 Cross-Section mis- MBL, but proﬁle measurements were also made up to sions were ﬂown along 20 S during REx (mission de- 3–4 km to capture aerosol layers and the vertical ther- tails shown in Fig. 6), with more ﬂown along nearby modynamic structure aloft. The BAe-146 missions also www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 642 R. Wood et al.: VOCALS operations Table 8. Details of G-1 aircraft missions conducted in the VOCALS Regional Experiment. Flight Date Times [UTC] Mission/Location Notes T/O Land 081014a Oct 15:54 18:26 19 S XS Solid clouds, repeated transects at different altitudes, below, in 14 and above clouds ◦ ◦ ◦ 081017a Oct 13:00 16:50 19 S XS Solid clouds, repeated transects between 73 and 74 W, 17 vertical proﬁle 081018a Oct 13:07 15:16 19 S XS Solid clouds, ﬂight aborted 081022a Oct 16:32 19:57 19 S XS Solid clouds, repeated transects at different altitudes, below, in 22 and above clouds, strong longitudinal gradient cloud and aerosol properties 081023a Oct 12:49 16:35 SW to Point Alpha Broken clouds, C130 intercomparison, repeated transects at 23 different altitudes, below, in and above clouds 081025a Oct 13:03 17:07 SW to Point Alpha Broken clouds, repeated transects at different altitudes, below, 25 in and above clouds, strong longitudinal gradient cloud and aerosol properties 081026a Oct 13:01 16:36 SW to Point Alpha, then Broken clouds, Twin Otter intercomparison, repeated transects 26 20 XS at different altitudes, below, in and above clouds, longitudinal gradient cloud properties 081028a Oct 12:58 17:16 18.5 S XS Clouds thicker to west, single transect below, in and above 28 clouds, strong longitudinal gradient in physical, cloud and aerosol properties 081029a Oct 15:58 19:33 Coastal pollution survey to Broken clouds, constant altitude to south, below, in and above 29 23 S clouds on return 081101a Nov 1 12:57 16:57 18.5 S XS Variable cloud structures, below, in and above clouds to west, constant altitude on return, strong longitudinal gradient in physical, cloud and aerosol properties ◦ ◦ 081103a Nov 3 12:58 16:51 18.5 S XS Clear-air near coast and at 72 W, repeated transects below, in, and above clouds ◦ ◦ ◦ 081104a Nov 4 11:57 16:02 SW to 19.5 S, 72 W Clear air near coast and at 72 W, C-130 intercomparison, repeated transects below, in and above clouds 081106a Nov 6 11:57 16:21 18.5 S XS Solid clouds, below, in and above clouds to west, constant altitude on return, strong longitudinal gradient in cloud and aerosol properties 081108a Nov 8 12:55 16:31 18.5 S XS Broken clouds, longitudinal gradient in cloud and aerosol properties ◦ ◦ 081110a Nov 13:02 16:50 SW to 20 S, 75 W Clear near coast, variable clouds to SW, below, in and above 10 clouds, short transects at SW terminus, strong longitudinal gradient in cloud and aerosol properties ◦ ◦ 081112a Nov 13:20 16:55 18.5 S XS Broken clouds at 73.5 W, solid elsewhere, below, in and above 12 clouds, short transects at W terminus, longitudinal gradient in cloud and aerosol properties 081113a Nov 12:54 16:41 18.5 S XS Mostly clear, below, in and above clouds to west, constant 13 altitude on return, longitudinal gradient cloud and aerosol properties included a return leg at an altitude of 5–7 km from 2. POC-drift missions which target either existing pock- which dropsondes were launched and nadir radiometers ets of open cells (POCs) within overcast stratocumulus, were operated. Three XS missions were conducted in or areas prone to POC development, and track these which three aircraft (C-130, BAe-146 and Do-228) all as they advect with the ﬂow. Focus in these missions conducted near-simultaneous cosampling, with the C- was on characterizing the marine boundary layer and the 130 sampling in the MBL, and the Do-228 and BAe- lowermost part of the free troposphere. A typical ﬂight 146 ﬂying in the free troposphere and serving as remote- plan is shown in Fig. 7, and a summary of the POC sam- sensing/dropsonde platforms; pling from the various platforms is given in Table 11. Some sawtooth runs provided additional vertical infor- mation without compromising too severely the number of straight and level ﬂight legs. On one occasion (27/28 Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ profile mean MBL wind profile R. Wood et al.: VOCALS operations 643 C-130 RF08, 2 Nov 2008 (a) (b) o o o 80 W 75 W 70 W Arica 20 S POC OVERCAST Stratocumulus OPEN CELLS 4-level stacks overcast drifting with stratocumulus the wind GOES Visible image, 13:15UTC OPEN CELL REGION OVERCAST STRATOCUMULUS REGION (c) free troposphere above-cloud leg cloud leg upper MBL cloud-base leg 1.5 km LCL surface mixed layer subcloud leg 150-250 km Fig. 7. POC-Drift mission ﬂight plan. (a) schematic of plan view; (b) example POC-Drift misson ﬂight track from C-130 Research Flight RF08 on 2 Nov 2008; (c) schematic cross section of boundary between open and closed cell regions showing sampling using long straight and level runs 150–250 km in length, proﬁles, and sawtooth sampling through the upper part of the MBL and lower troposphere. Due to its reduced range the BAe-146 sampled a subset of the C-130 ﬂight plan when sampling POCs. October 2008) it was possible to sample the same ad- within the MBL and in the lower free troposphere, but vected POC with two aircraft missions spaced approxi- occasional proﬁles up to 3–4 km altitude were also em- mately 12 h apart; ployed. Figure 2 shows the typical locations of these ﬂights. The BAe-146 and C-130 aircraft performed the 3. Stacked cloud and/or radiation missions in which one bulk of the pollution survey sampling, with six ﬂights or two aircraft sample a cloudy boundary layer air- dedicated to this mission type; mass, typically using stacked legs 50–100 km in length. 5. Intercomparison ﬂights, either aircraft-aircraft (at sev- For two-aircraft missions, the upper aircraft primarily eral different ﬂight levels both in and above the MBL) served as a radiation/remote sensing platform and ﬂew or to compare aircraft and ship measurements (with the in the free troposphere. All the aircraft other than the aircraft ﬂying at its lowest possible ﬂight level, typ- C-130 carried out missions of this type. All Twin Otter ically 150 m). The summary of intercomparisons is missions were of this type, and additionally were car- given in Table 12. ried out at the same location (at so-called “Point Alpha”, ◦ ◦ 20 S, 72 W); Tables 6, 7, 8, 9, and 10 present the speciﬁc missions ﬂown by the C-130, BAe-146, G-1, Do228, and Twin Otter respec- 4. Pollution Survey missions in which aircraft sampled tively. within a few hundred km of the Peruvian and Chilean coasts, with the aim of characterizing the lower at- 4.3 Ship sampling mosphere in the vicinity of pollution source regions. These missions replaced the polluted Lagrangian mis- 4.3.1 Peruvian R/V Jose ´ Olaya sions which had been originally planned for VOCALS- REx, because it became clear that Lagrangian missions Figure 8 shows the track of the R/V Jose ´ Olaya during starting around 20–25 S would not sample sufﬁciently the VOCALS REx cruise (2–17 October 2008). A total of close to the major pollution sources to capture the ag- 133 radiosonde soundings were acquired at varying spatio- ing process. Emphasis was placed on sampling both temporal intervals from 30 September to 17 October 2008. www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 Flight Track ~150-250 km l 644 R. Wood et al.: VOCALS operations Table 9. Details of Do-228 aircraft missions conducted in the VOCALS Regional Experiment. Flight Date Times [UTC] Mission/Location Notes T/O Land VA01 Oct 26 14:16 17:27 Test ﬂight VA02 Oct 28 12:49 14:30 Test ﬂight VA03 Oct 30 11:38 15:48 Overﬂy RHB at 19 35.5’S, Stacked cloud/radiation over RHB and FAAM BAe146 74 46.9’W ◦ ◦ VA04 Oct 31 11:30 15:26 20 S cross-section To point alpha at 4800 m then west to 76 W, retracing path ◦ ◦ VA05 Nov 2 11:54 15:11 Proﬁling, to 19.5 S, 74.5 W Six vertical proﬁles, cloud top–4800 m, followed by spiral descent and return to Arica at 3400 m VA06 Nov 3 13:00 16:36 Coastal pollution gradient Flew to Peruvian border at 4000 m, then followed same path as FAAM BAe146 to DART buoy; back at 3300 m VA07 Nov 4 11:31 15:43 20 S cross-section As VA04 except return leg at 3400 and 3200 m VA08 Nov 5 13:00 16:11 Proﬁling ﬂight south to Proﬁling coastal pollution between cloud top and 4800 m ◦ 0 ◦ 0 22 39 S, 71 10 W VA09 Nov 6 18:35 20:14 Lidar test Flew to point alpha and back between 4000 and 5000 m VA10 Nov 9 13:39 17:52 20 S cross-section as VA04 VA11 Nov 10 11:23 15:23 Loop south to 22.4 S 4800 m; overﬂight of FAAM BAe146 VA12 Nov 12 11:35 12:19 Flight aborted Problem with aircraft VA13 Nov 13 10:05 11:45 Intercomparison with BAe-146 Legs at 200 m–3 km altitude VA14 Nov 13 12:45 16:48 20 S cross-section As VA04 except return leg at 4200 m VA15 Nov 14 13:15 16:51 Vertical proﬁling to 22.5 S 8 vertical proﬁles, 100–4800 m characterize the physical properties of the upwelling plume VOCALS Peru and the associated thermal front. A cluster of 8 surface 12 S Callao 02−17 October, 2008 drifters were deployed across the upwelling front in order to study the advective and diffusive processes inside this fea- 13 S Cerro Azul ture. The glider (autonomous underwater vehicle) mission was designed to examine the high-resolution structure and Tambo de Mora Pisco dynamics of the upwelling plume and thermal front off Pisco o 70 14 S between 10 km and 100 km from the coast. The distribu- Bahia Independencia 60 tion of biogeochemical and biological parameters as well as ﬁsh abundance were also sampled to study the feedback of o Punta Caballas 15 S ocean/atmosphere interactions on biological and ﬁshery ac- San Juan tivity. 16 S 4.3.2 NOAA R/V Ronald H. Brown Glider section CTD casts (0−1000m) 17 S Radiosondes Figure 9 shows the track of the NOAA R/V Ronald H. Brown Multi-disciplinary casts (RHB) during the VOCALS REx cruise (25 October to 2 De- o o o o o o o 80 W 79 W 78 W 77 W 76 W 75 W 74 W cember 2008). The cruise was planned and carried out as two legs: Leg 1 took place between 29 September to 3 Novem- Fig. 8. Cruise track (black, with white for transit legs) and sam- ber 2008 (arriving in the VOCALS-REx domain on 24 Oc- pling from the IMARPE R/V Jose ´ Olaya during the VOCALS Peru tober 2008) and the RHB spent the majority of the time sta- cruise (2–17 October 2008). The color contours show the October- mean (1997–2004) daytime clear sky fraction determined using the tioned at the IMET and DART mooring where recovery and SeaWIFS cloud clearing algorithm. redeployment of the moorings took place; Leg 2 took place between 9 November and 2 December 2008 and involved mapping the structure of the upper ocean and observing the atmosphere exclusively in the VOCALS-REx domain. Launch sites were predominately within the upwelling zone, about 200 km from the coast of the Pisco-San Juan upwelling After the RHB arrived in the VOCALS-REx domain, all ◦ ◦ region. Temperature, salinity and currents were measured to of the sampling took place between 18 S and 22 S. Both Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ clear sky occurrence [%] R. Wood et al.: VOCALS operations 645 Table 10. Details of Twin Otter aircraft missions conducted in the VOCALS Regional Experiment. Flight Date Times [UTC] Mission/Location Notes T/O Land ◦ ◦ 01 Oct 16 14:16 17:27 Stacked turbulence/aerosol/cloud At Point Alpha (20 S, 72 W) 15:10–17:50 02 Oct 18 12:49 14:30 Stacked turbulence/aerosol/cloud At Point Alpha 12:15–15:00 03 Oct 19 11:38 15:48 Stacked turbulence/aerosol/cloud At Point Alpha 12:05–14:40 04 Oct 21 11:30 15:26 Stacked turbulence/aerosol/cloud At Point Alpha 12:10–14:50 05 Oct 22 11:54 15:11 Stacked turbulence/aerosol/cloud At Point Alpha 12:00–14:40 06 Oct 24 13:00 16:36 Stacked turbulence/aerosol/cloud At Point Alpha 12:15–15:00 07 Oct 26 11:31 15:43 Stacked turbulence/aerosol/cloud At Point Alpha 12:00–15:00 08 Oct 27 13:00 16:11 Stacked turbulence/aerosol/cloud At Point Alpha 15:55–19:00 09 Oct 29 18:35 20:14 Stacked turbulence/aerosol/cloud At Point Alpha 11:50–15:00 10 Oct 30 13:39 17:52 Stacked turbulence/aerosol/cloud At Point Alpha 11:50–15:00 11 Nov 1 11:23 15:23 Stacked turbulence/aerosol/cloud At Point Alpha 12:05–15:05 12 Nov 2 11:35 12:19 Stacked turbulence/aerosol/cloud At Point Alpha 11:55–15:00 13 Nov 4 10:05 11:45 Stacked turbulence/aerosol/cloud At Point Alpha 11:50–14:40 14 Nov 5 10:00 16:50 Stacked turbulence/aerosol/cloud At Point Alpha 11:50–15:00. Cloud/aerosol probe data failed 15 Nov 8 12:45 16:48 Stacked turbulence/aerosol/cloud At Point Alpha 11:50–15:00 16 Nov 9 13:15 16:51 Stacked turbulence/aerosol/cloud At Point Alpha 11:50–15:05 17 Nov 10 13:15 16:51 Stacked turbulence/aerosol/cloud At Point Alpha 14:45–18:00 18 Nov 12 13:15 16:51 Stacked turbulence/aerosol/cloud At Point Alpha 11:50–15:15 19 Nov 13 13:15 16:51 Stacked turbulence/aerosol/cloud At Point Alpha 12:00–14:50 Legs 1 and 2 involved studies of the ocean, the atmosphere, a greater range of statistical variability, more chemical de- and their coupling as part of VOCALS-REx. Leg 1 focused tail (such as organic functional groups, see Hawkins et al., primarily upon measurements at the IMET and SHOA buoys, 2010), and highly accurate standards as references (such as while Leg 2 involved more surveying of mesoscale ocean ion chromatography) that are complementary to the aircraft- features. The sampling strategy for Leg 2 was optimized dur- based data sets. In addition, the measurement of radon on the ing the “all-hands” meeting in Arica between legs, the adjust- RHB permits an assessment of the time that airmasses have ments being necessary because operational delays reduced spent over the ocean. The RHB studies of aerosol properties the Leg 1 sampling by almost 10 days which compromised provide a comprehensive basis for addressing the variabil- the mesoscale surveying during Leg 1. Coordinated sam- ity in physicochemical properties. These measurements also pling with research aircraft working from Arica and Iquique serve as the basis for comparison of the sources and compo- took place during both cruises, with the majority of coordi- sition of the aerosol particles, providing comprehensive in- nated sampling taking place during Leg 2 (see Tables 6 to 9 formation with which to compare to satellite-retrieved prop- for details of RHB-aircraft cosampling. erties. A total of 210 radiosondes were obtained at 4 h intervals The main objectives of the oceanographic ﬁeld work con- within the marine stratocumulus region. The ship sampled ducted from the R/V Ron Brown (Legs 1 and 2) were: (i) to multiple times across relatively sharp transitions of cloud map the mean and eddy (mesoscale/submesoscale) tempera- coverage including clear to broken to overcast stratocumu- ture, salinity and velocity distribution within the SEP’s upper lus cloud conditions. It was overcast approximately 80% ocean during VOCALS-REx; (ii) to deploy Lagrangian ﬂoats of the time. Drizzle was prevalent: drizzle-containing cells and drifters within the SEP; (iii) to recover and re-deploy with signiﬁcant radar reﬂectivity (Z > 0 dBZ) were observed the STRATUS and DART moorings. The synoptic survey within a 60 km radius of the ship roughly half the time. The across the SEP region included the collection of 35 CTD RHB research cruise for VOCALS-Rex was designed to ad- (Conductivity, Temperature, Depth proﬁles) up to 2000 m dress important aspects of both (1) aerosol-cloud-drizzle hy- depth, and of 438 UCTD (Underway CTD) proﬁles, rang- potheses and (2) coupled ocean-atmosphere hypotheses. ing between 200 and 800 m deep, to map the meridional Aerosol-cloud-drizzle interactions vary in both space and distribution of properties across the SEP along three dis- time at a multitude of scales. The ship provided a platform tinct latitude lines (Fig. 9). During the surveys, spatial and to investigate in detail aerosol distributions and composition, temporal sampling was increased to resolve a number of including diurnal patterns during slow transects over much oceanic fronts and eddies, including 4 cyclones, 2 anticy- smaller regions of the marine boundary layer than is covered clones, the coastal currents and upwelling front at 21.5 S. by the aircraft in a single hour. For this reason, the nearly Microstructure proﬁles to quantify mixing rates were ob- 60-day cruise provided measurements of marine aerosol with tained using a Vertical Microstructure Proﬁler (VMP) at 15 www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 646 R. Wood et al.: VOCALS operations Table 11. Details of POC sampling/missions conducted in the VOCALS Regional Experiment. Aicraft Flight Date Times [UTC] Details T/O Land ◦ ◦ C-130 RF02 Oct 18 13:04 21:27 Daytime mission. Sampling of rift-like feature at 21 S, 82.5 W ◦ ◦ BAe-146 B409 Oct 27 19:59 00:29 Late afternoon mission. POC edge sampled at 21 S, 77.5 W . First ﬂight of POC Lagrangian mission with C-130 ﬂight RF06 ◦ ◦ C-130 RF06 Oct 28 06:20 15:10 Night mission. Very clear POC edge sampled at 18 S, 80 W. Second ﬂight of POC Lagrangian mission with BAe-146 ﬂight B409 ◦ ◦ C-130 RF07 Oct 31 06:03 14:58 Night mission. Sampling of recently-formed POC at 21.5 S, 80 W which was growing and spreading to the north. C-130 RF08 Nov 2 06:00 15:20 Night mission. Sampling of a pronounced microphysical boundary at ◦ ◦ 22 S, 80 W between a polluted tongue of stratocumulus and a very clean airrmass with precipitating open cells to south. Pronounced difference in MBL height across boundary. C-130 RF09 Nov 4 06:02 14:54 Night mission. POC sampling across a boundary between polluted ◦ ◦ stratocumulus tongue and very clean airmass at 22 S, 80 W. Boundary less well-pronounced than in other cases and overcast stratocumulus appeared to be breaking up during ﬂight. BAe-146 B415 Nov 5 09:12 14:33 Early morning mission. Open cellular region sampled at ∼78 W. BAe-146 B416 Nov 7 10:32 15:27 Morning mission. Open cellular region sampled at ∼78 W. BAe-146 B420 Nov 13 09:58 15:13 Morning mission. POC sampled brieﬂy at western point at ∼81 W. C-130 RF13 Nov 13 13:00 21:55 Day mission, Extensive clearing near coast, then thick cloud with ◦ ◦ recently-formed POC at 19 S, 78 W ◦ ◦ C-130 RF14 Nov 15 13:00 22:00 Day mission, rift/clearing sampled, high SO just above MBL at 21 S, 80 W Table 12. Details of the intercomparisons conducted VOCALS-REx. Platform BAe-146 G-1 Twin Otter Do-228 RHB Paposo 1. 10/25 (RF05, 1. 10/31 IMET Buoy) 1. 11/9 (RF11, 1. 10/23 (RF04) (RF07/B412) 2. 11/02 (RF08, along 73W) C-130 None None 2. 11/04 (RF09) 2. 11/04 SHOA Buoy) 2. 11/11 (RF12, (RF09/B414) 3. 11/11 (RF12, along 73W) near SHOA buoy) 1. 10/30 (near 1. ground SHOA Buoy) 11/13 BAe-146 – None None comparison 2. 11/12 (near (B420/VA13) 2. 11/12 (B419) SHOA buoy) G-1 – – 10/26 None None None 11/10 (near Twin Otter – – – None None SHOA buoy) Do-228 – – – – 10/30 VA03 None RHB – – – – – None different locations that included the centers and margins of viding direct observations of the velocity ﬁeld within the ed- several of the eddies/fronts. The velocity structure of the up- dies, fronts and boundary currents to complement the prop- per 300–500 m, along the ship track, was observed by the erty measurements. In addition to the synoptic measure- ship’s Acoustic Doppler Current Proﬁler (ADCP) – thus pro- ments conducted during VOCALS-REx, the deployment of Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ R. Wood et al.: VOCALS operations 647 Leg 1 Split-window Technique (VISST). At night, cloud properties IMET or DART/SHOA Mooring Ronald H Brown Leg 2 were retrieved using the Shortwave-infrared Infrared Split- Argo (SOLO) float release CTD Surface drifter release CTD+VMP window Technique (SIST). The methods are described in de- 16 17 18 19 20 21 tail for application to MODerate-resolution Imaging Spectro- -4 cm +4 cm SST [C] SSH contours radiometer (MODIS) data by Minnis et al. (2008, 2010). The −18 VISST uses the 0.65, 3.9, 10.8, and 12.0 μm channels, while −18.5 C3 A2 C2 the SIST uses the same channels minus the 0.65 μm data. The −19 GOES-10 0.65 μm channel was calibrated against the Terra C1 −19.5 MODIS 0.64 μm channel using the technique of Minnis et al. (2002). The available derived parameters and means of ac- −20 cessing the data are similar to those described by (Palikonda −20.5 et al., 2006). Both pixel-level and 0.5 × 0.5 averages are −21 available each hour in image and digital form . The VISST A3 −21.5 and SIST assume that only single-layer clouds are in a given C4 −22 pixel. In addition to the standard approach described by Min- −86 −84 −82 −80 −78 −76 −74 −72 −70 nis et al. (2010), cloud-top height and pressure were also re- trieved using the method described by Zuidema et al. (2009). Fig. 9. Cruise tracks for Legs 1 and 2 of the NOAA R/V Ron Brown One additional parameter, a multilayer cloud identiﬁer was during VOCALS-Rex superimposed on the sea-surface tempera- ture (SST) and sea-surface height (SSH) from November 18th 2008 computed for each pixel using the approach of Pavolonis and (middle of Leg 2; courtesy of P. Gaube and D. Chelton, OSU). Heidinger (2004). In addition to the cloud properties, spec- The 438 underway CTDs (UCTD) are overlaid as white dots on tral radiances and estimates of the top-of-atmosphere short- the two tracks. Also shown are the locations of the 35 CTDs and wave albedo and outgoing longwave radiation are included. 15 VMP (microstructure) proﬁles as well as those where 19 surface Figure 10 shows an example of three parameters for a drifters and 10 proﬁling SOLO ﬂoats were deployed. Several of GOES-10 image taken at 15:45 UTC, 27 October 2010. The the sampled cyclones and anticyclones are indicated by a C and A, pseudo-color RGB image (Fig. 10a) shows low clouds in respectively, followed by a sequential number. the orange and peach shades with high cirrus clouds appear- ing white, gray, and magenta. The effective cloud tempera- tures T are displayed in Fig. 10b for an abbreviated range 10 proﬁling Lagrangian ﬂoats (SOLO ﬂoats, equipped with of 273 K < T <300 K to better show variations in stratocu- an oxygen sensor) and 19 surface drifters – some in ed- mulus cloud temperatures. Temperatures less than 273 K dies and some throughout the SEP – were designed to pro- are indicated in the maroon shade. For this case, T ranges vide long-term context to the synoptic measurements – to- from 274 K to 284 K for the marine stratocumulus clouds. gether with the instruments recovered and re-deployed on the Smaller values are evident where thin cirrus clouds occur IMET/STRATUS and DART buoys. over the low clouds. Cloud optical depths (Fig. 10c) range from less than 1 at some cloud edges to more than 40 near ◦ ◦ 18 S, 78 W. The VISST-derived droplet effective radius, re, 5 Satellite datasets produced speciﬁcally for (Fig. 10d) varies from about 7 to 25 μm across the scene VOCALS-REx with most of the largest values occurring around the edges of the POCs. The smallest droplets are mostly near the coast. 5.1 Geostationary Operational Environmental The pixel-level products, exempliﬁed in Fig. 10a–d, are used Satellites, GOES-10 to produce 0.5 × 0.5 regional means at each half hour for 5.1.1 Visible Infrared Solar-Infrared Split Window many of the cloud and radiation parameters (Palikonda et al., Technique (VISST) 2006). Examples of 0.5 × 0.5 regionally-averaged cloud top-height Z and liquid water path (LWP) are shown in Cloud and radiation parameters at 4-km resolution were Fig. 10e, f. The Z values estimated as in Minnis et al. (2010) derived from the tenth Geostationary Operational Environ- range from less than 1 km up to more than 3 km in the south- mental Satellite imager (GOES-10), located at 60 W, us- western portion of the domain. Higher clouds near the cen- ing techniques developed at NASA Langley Research Cen- ter of the domain correspond to the thin cirrus clouds over ter (LaRC). The GOES-10 data were analyzed every half the stratocumulus deck. The heights based on the Zuidema ◦ ◦ ◦ hour for the region bounded by 10 S, 30 S, 65 W, and et al. (2009) technique are generally lower (not shown). The −2 90 W for the period between 11 September and 1 Decem- cloud LWP ranges from less than 50 g m along the coast −2 ber 2008 and provided in near-real time for mission planning to over 200 g m near the center of the domain. The LaRC and analysis. Clouds were detected using the method of Min- nis et al. (2008) and cloud properties were retrieved during Available from http://www-angler.larc.nasa.gov/cgi-bin/site/ the daytime using the Visible Infrared Shortwave-infrared showdoc?mnemonic=VOCALS www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 648 R. Wood et al.: VOCALS operations Fig. 10. GOES-10 imagery and retrieved cloud parameters, 15:45 UTC, 27 October 2008: (a) pseudocolor RGB image; (b) cloud effective temperature [K]; (c) cloud optical depth; (d) cloud liquid water droplet effective radius [μm]. Regional (0.5 × 0.5 ) average cloud properties, (e) cloud top height, and (f) cloud liquid water path for the same time. cloud properties are based on near-real time retrievals. A re- the VOCALS-REx period. The GOES-10 data were ana- ﬁned dataset using the latest GOES-10 calibrations, a higher lyzed between 1 October and 8 December 2008 in a re- ◦ ◦ resolution sea surface temperature dataset, and algorithm up- gion from 3.5–31.5 S and 68.5–96.5 W. Note that this is dates is being generated to provide a more accurate set of a more extensive region than for the VISST GOES-10 prod- cloud properties for stratocumulus research and for compari- ucts described above. Clouds are classiﬁed on all available son with the other experiment measurements to better deﬁne GOES-10 scans (typically every 15 to 30 min) at a horizon- the uncertainties in the satellite products. tal resolution of 4 km, and cloud cover fractions are gridded at 0.25 × 0.25 resolution. Further details are given in Abel et al. (2010), and the dataset is available on the VOCALS 5.1.2 Gridded cloud cover product from the University archive, described below. of Manchester/Met Ofﬁce 5.2 MODIS subset Thermal infrared data from GOES-10 (Channel 4, 10.7 μm), converted to netCDF format and archived on the VOCALS data archive (see Sect. 8), have been used to generate a A dedicated subset of MODIS imagery from NASA’s Terra dataset documenting the variability in cloud amount during and Aqua satellites for the VOCALS-REx study region is Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ R. Wood et al.: VOCALS operations 649 available for browsing on the MODIS Rapidﬁre website with a broader group of coupled ocean-atmosphere mod- http://rapidﬁre.sci.gsfc.nasa.gov/subsets/?subset=VOCALS. els. All aircraft included cloud physics, turbulence and aerosol/chemical composition measurements for testing the representation of aerosol/cloud interaction in models; the 6 Coordinated modeling for VOCALS-REx Wyoming Cloud Radar on the C-130 also added precipita- tion proﬁles into this dataset. This integrated suite of mea- 6.1 Overview of the VOCALS modeling program surements provides a strong constraint on simulations of SEP clouds and aerosols. Synthesis papers by Bretherton et al. An overarching goal of VOCALS is to improve model sim- (2010) (boundary layer and physical cloud properties) and ulations of key climate processes using the SEP as a testbed, Allen et al. (2011) (aerosol and chemical composition) sum- particularly in coupled models that are used for climate marize the results of the REx 20 S measurements in multi- change projection and ENSO forecasting. Hence, REx was platform 20 S synthesis datasets that will be part of the EOL developed in close coordination with the VOCALS modeling VOCALS data archive and are designed to be convenient program, whose main goals are: for comparison with large-scale models. Modeling studies by Rahn and Garreaud (2010a,b) and Abel et al. (2010) fo- 1. Understanding and reducing the warm SEP SST bias cus on comparison with REx 20 S measurements. The VO- near the coast and excessive interhemispheric symme- CALS assessment (see Sect. 6.3) was also conceived as an try in the eastern tropical Paciﬁc present in most cou- integrated part of REx, and will make use of the REx 20 S pled climate models. synthesis datasets. 2. Using the SEP as a testbed for better simulation of The REx POC missions were designed for comparison boundary layer cloud processes and aerosol-cloud inter- with large-domain LES of cloud-aerosol-precipitation inter- action, including the relative roles of natural and anthro- action, and modeling papers utilizing these REx datasets are pogenic aerosol sources and their impact on cloud opti- already emerging, e.g. Wang et al. (2010). cal properties (coverage, thickness, and droplet size). REx ship-based sampling of mesoscale ocean eddies was also envisioned to complement and test a regional eddy- 3. Improving the understanding and simulation of oceanic resolving (5 km resolution) ocean model run in data assim- budgets of heat, salinity, and nutrients in the SEP and ilation mode; such modeling efforts are underway. their feedbacks on the regional climate. 6.2 Real-time modeling during REx 4. Elucidating interactions between the SEP and other parts of Earth’s climate system, including the South Several modeling groups supported VOCALS-REx mission American continent, the Paciﬁc circulation and ENSO. planning and ﬁeld data interpretation through provision of The VOCALS modeling vision is based on the concept plots from real-time forecasts. This also provided those of a multiscale hierarchy of models, both in time and space. groups a good opportunity to evaluate their models in the This is motivated by the multiscale nature of processes in the ﬁeld. These forecast products are archived in the VOCALS- SEP and the multiscale hierarchy of VOCALS observations, REx Field Data Catalog ; they remain a useful “quick-look” including REx, extended in-situ and satellite data. In this resource. They include plots of simulated regional meteoro- spirit, one VOCALS modeling goal is to test models used for logical ﬁelds, vertical proﬁles, trajectories and cross-sections long-term climate projection as rigorously as possible by ap- of selected ﬁelds and chemical constituents, especially along plying them on a different timescale, namely the short period 20 S, and some regional zonal cross-sections through the up- of intensive data gathering during REx, by testing them in per ocean. a weather forecasting mode. Another goal is to compare ob- A synopsis of contributed and archived real-time products servations with models of various horizontal and vertical res- follows. olutions, e.g. higher-resolution regional models vs. coarser- resolution global models. A third goal is to test and apply 6.2.1 UKMO small-scale process models, e.g. large-eddy simulation (LES) models of the cloud-topped boundary layer, which can in- The UK Met Ofﬁce (UKMO) submitted 20 S cross-sections form our physical understanding and help guide the develop- and horizontal maps of a variety of ﬁelds from their opera- ment of parameterizations for larger-scale models. tional weather forecast model, the Uniﬁed Model (UM), run Many aspects of REx were designed to facilitate these at 40 km resolution globally, and from a 17 km resolution re- modeling goals. The atmospheric observation strategy gional version of the UM nested inside their global model. included repeated airborne and ship-based measurements In addition they contributed real-time forecasts from their along one transect, 20 S, to facilitate comparison with global Numerical Atmospheric Dispersion Modeling Environment and regional atmospheric models used in forecast mode and to provide a rough climatology that could be compared Available at http://catalog.eol.ucar.edu/vocals/ www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 650 R. Wood et al.: VOCALS operations (NAME) dispersion/chemical transport model, also run at simulation after 10 days. The resulting tracer concentrations 17 km horizontal resolution. should be regarded as excesses above any background asso- ciated with other more broadly based SO emission. 6.2.2 ECMWF 6.2.8 Ocean state The European Center for Medium-Range Weather Forecasts Both ECMWF and NCEP also provided selected zonal cross- (ECMWF) global forecast system, run at T399 and T799 res- sections of upper ocean temperature and salinity from their olution, provided selected ﬁelds along 20 S and a regional operational coupled modeling systems. cloud analysis. High resolution analyses are available for the REx period through the Year of Tropical Convection (YoTC) 6.3 Model intercomparison studies for Rex project . Two model intercomparison studies have been organized in 6.2.3 NCEP coordination with REx. The ﬁrst was the Pre-VOCALS As- sessment or PreVOCA (Wyant et al., 2010). It was designed A variety of ﬁelds were archived from short-range opera- to assess the skill of current global and regional atmospheric tional global weather forecasts by the US National Centers models in forecasting subtropical South East Paciﬁc cloud for Environmental Prediction (NCEP), run at approximately and marine boundary layer (MBL) characteristics in prepa- 50 km resolution. ration for REx. The 15 participating models represented 6.2.4 NRL the state of the art in simulation of the SE Paciﬁc and other boundary-layer cloud regimes. They simulated the month of The Naval Research Laboratory (NRL) contributed real-time October 2006 and were compared in the region from 40 S to ◦ ◦ forecasts with their COAMPS (Coupled Ocean Atmosphere the equator and from 110 W–70 W. Satellite datasets and Mesoscale Prediction System) regional model using three rawinsondes from research cruises in the region were used nested grids (with resolutions of 45, 15 and 5 km, with the for validation. Each model was run in some form of “fore- 15 km domain extending over the entire REx region). Plots cast mode”. Global models were initialized using a global include cloud and lower-tropospheric meteorological ﬁelds. analysis and compared based on short-range forecasts, while regional models were continuously forced at their boundaries 6.2.5 U. Chile using reanalysis data. A few models showed considerable skill in reproducing the monthly mean, day-to-day variabil- The University of Chile contributed plots of cloud and ity and diurnal cycle of cloud cover and MBL structure across boundary layer ﬁelds from short-range forecasts with their the region, though all models had a low bias in MBL inver- version of the Weather Research and Forecasting (WRF) re- sion height near the Chilean coast. gional model run at 25 km resolution. PreVOCA was designed to prepare VOCALS modeling groups for a more ambitious followon, the VOCALS assess- 6.2.6 UW trajectories ment or VOCA based on the REx period of 15 October–15 November 2008. This assessment, which is ongoing, makes Rhea George of the University of Washington plotted a va- use of the extensive in-situ data (especially along 20S) to test riety of short-range forward and back isobaric and three- chemical transport, aerosol and drizzle processes in simu- dimensional trajectories from selected points and altitudes lations of the SE Paciﬁc regions, as well as evaluating the along the 20 S line, based on NCEP GFS wind analyses and time-varying cloud and MBL structure. Both global and re- short-range forecasts. gional climate models with chemical transport capabilities are participating. Global models each use their own chem- 6.2.7 FLEXPART particle dispersion model ical emissions inventory; a custom-designed regional emis- sions inventory was developed by Dr. Scott Spak of U. Iowa The FLEXPART Lagrangian particle dispersion model for use in regional models. Of particular interest is whether (Stohl et al., 2005), with a horizontal resolution of 0.5 × 0.5 , such models can simulate the observed offshore gradients of and 26 vertical levels, was driven by GFS forecast winds. accumulation model aerosol concentration and cloud droplet Millions of passive tracer particles in FLEXPART were con- concentration in the boundary layer. This is timely, since tinuously released, corresponding to point and distributed many global climate models have recently implemented rep- sources of South American anthropogenic and volcanic SO resentations of aerosol indirect effects on cloud properties. transported both by the resolved GFS winds and parame- terized subgrid motions, until they were removed from the See http://www.ucar.edu/yotc/ 5 6 Available at http://www.esrl.noaa.gov/csd/metproducts/ See http://www.atmos.washington.edu/ mwyant/vocals/ ﬂexpart/ model/VOCA Model Spec.htm Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ R. Wood et al.: VOCALS operations 651 CCN Cloud Condensation Nuclei, particles that 7 VOCALS data management nucleate at a given instrumental water vapor supersaturation, generally a fraction up to a The NCAR/EOL provided data management support, coor- few percent supersaturation. dination, and a long-term archive for VOCALS datasets. De- CLIVAR Climate Variability and Predictability, component of World Climate Research tails regarding VOCALS Data Management can be found on Programme the VOCALS Project web page . This web page contains CN Condensation Nuclei, particle concentration the VOCALS data policy, instructions for data submission, larger than given diameter, ca. 10 nm. relevant documentation, links to related projects data, and Ultraﬁne CN Condensation Nuclei, particle concentration larger than given diameter, ca. 3 nm. access to the distributed VOCALS long-term archive [i.e. CPC Condensation Particle Counter, instrument to Master List (ML) of VOCALS International Datasets]. The measure CN ML contains direct access to all datasets organized by data CTD Conductivity, Temperature, Depth category and data source site with associated dataset doc- measurement CUpEx Chilean Upwelling Experiment umentation. In addition, the VOCALS-Rex Field Catalog DART/DB Deep-ocean Assessment and Reporting of used during the ﬁeld phase to provide operations and mis- Tsunamis, buoy site sion/scientiﬁc reports, operational and preliminary research DMS Dimethyl sulﬁde DMSP Dimethylsulfonium propionate imagery/products is available as a browse tool for use by re- Do-228 NERC Dornier, DO-228 research aircraft searchers in the post-ﬁeld analysis phase and is included as DOE Department of Energy part of the archive. EDGAR Emission Database for Global Atmospheric Research FAAM Facility for Airborne Atmospheric 8 Conclusions Measurements (United Kingdom) FIMS Fast Integrated Mobility Spectrometer G-1 DoE Gulfstream-1 research aircraft The VOCALS Regional Experiment (VOCALS-REx) was an IMARPE Instituto del Mar del Per international ﬁeld experiment designed to examine critical IMET/STRATUS/ Improved Meteorology buoy aspects of the coupled climate system of the Southeast Pa- IB ciﬁc region. VOCALS-REx took place during October and MAX-DOAS Multi-Axis Differential Optical Absorption ◦ ◦ November 2008 in a domain 69–86 W, 12–31 S. Sampling Spectroscopy MBL Marine Boundary Layer with a variety of platforms including two ship, ﬁve research NCAR EOL National Center for Atmospheric Research aircraft, land sites and two instrument moorings will ensure Earth Observation Laboratory that researchers have a number of different observational an- NERC Natural Environment Research Council gles with which to test the VOCALS hypotheses. The pur- OPC Optical Particle Counter pose of this paper is to bring together in one document the PAN Peroxy acetylnitrate PCASP Passive Cavity Aerosol Spectrometer Probe scientiﬁc goals, the platforms and instrumentation, and the POC Pocket of Open Cells sampling strategies employed during the program. It is hoped PSAP Particle Soot Absorption Photometer that this will serve the VOCALS research community by pro- PTRMS Proton transfer reaction mass spectroscopy viding a central location that describes the essence of the ﬁeld RHB NOAA Research Vessel Ronald H. Brown program. Perhaps more importantly, we hope that it will help SEM-EDX Scanning Electron Microscopy Energy to provide an important legacy that will be available to re- Dispersive X-ray SEP South East Paciﬁc searchers over the coming years. SHOA Servicio Hidrogﬁco y Oceanogrﬁco de la Armada de Chile buoy SMPS, DMPS Scanning Mobility Particle Sizer or Appendix A Differential Mobility Particle Sizer SP2 Single Particle Soot Photometer SST Sea Surface Temperature Acronyms used in this manuscript STXM-NEXAFS Scanning Transmission X-ray Microscopy AMS Aerosol Mass Spectrometer Near Edge X-ray Absorption Fine Structure TDMA, TSEMS Tandem Differential Mobility Analyzer, BAe-146 FAAM British Aerospace BAe-146 research Tandem Scanning Electrical Mobility System aircraft C-130 NSF/NCAR Lockheed C-130Q research TRAC Time Resolved Aerosol Sampler aircraft UCTD Underway Conductivity, temperature, depth CAPS Cloud Aerosol And Precipitation measurement Spectrometer VAMOS Variability of the American Monsoon Systems VM-ADCP Vessel Mounted Acoustic Doppler Current Proﬁler VOCALS VAMOS Ocean-Cloud-Atmosphere-Land Study Available at http://www.eol.ucar.edu/projects/vocals/dm/index. WHOI Woods Hole Oceanographic Institute html Located at http://catalog.eol.ucar.edu/vocals/ www.atmos-chem-phys.net/11/627/2011/ Atmos. Chem. Phys., 11, 627–654, 2011 652 R. Wood et al.: VOCALS operations Acknowledgements. It is practically impossible to acknowledge all FONDECYT grants 1109004 and 1090412; the Swedish Research the people who have contributed to VOCALS, but we can try to pay Council for Environment, Agricultural Sciences and Spatial tribute to the various groups that have dedicated their resources, ef- Planning grant 2007-1008; The Met Ofﬁce (UK); the UK Nat- forts, sweat and tears to the planning and execution of the program. ural Environment Research Council grants NE/F019874/1 and First, we need to thank the teams led by Bob Weller at WHOI that NE/F018592/1; NSF-NCAR Cooperative Agreement: 0301213 deployed and maintained with annual cruises the IMET buoy which Amendment 64 funded VOCALS Field Support; Meteo France. has provided almost a decade of high quality meteorological, ra- diation and oceanographic measurements. Thanks to Chris Fairall Edited by: G. Feingold and coworkers at ESRL, and the scientists involved in the EPIC Stratocumulus cruise, these ship-borne data have led to a wealth of scientiﬁc data. We are extremely grateful to the support staff, crew References and scientists who helped make the VOCALS-REx a success. These include the PIs, support scientists and crews of the six aircraft plat- Abel, S. J., Walters, D. N., and Allen, G.: Evaluation of stra- forms (the NSF/NCAR C-130, the UK FAAM BAe-146, the DoE tocumulus cloud prediction in the Met Ofﬁce forecast model G-1, the CIRPAS Twin Otter, the UK NERC Dornier 228, and, in during VOCALS-REx, Atmos. Chem. Phys., 10, 10541–10559, the 2010 CUpEx phase, the Chilean DGAC King Air), the two ships doi:10.5194/acp-10-10541-2010, 2010. (the NOAA Ronald H. Brown, and the Peruvian IMARPE Jose ´ Ackerman, A. S., Kirkpatrick, M. P., Stevens, D. E., and Toon, Olaya), and the land stations at Iquique and Paposo. The NCAR O. B.: The impact of humidity above stratiform clouds on in- Earth Observing Laboratory is thanked for their dedication to coor- direct aerosol climate forcing, Nature, 432, 1014–1017, 2004. dinating and executing ﬁeld logistics and data archive support for Allen, G., Coe, H., Clarke, A., Bretherton, C., Wood, R., Abel, S. J., VOCALS REx. The cooperation of hosts and collaborators in Chile Barrett, P., Brown, P., George, R., Freitag, S., McNaughton, C., and Peru who provided various critical facilities and support during Howell, S., Shank, L., Kapustin, V., Brekhovskikh, V., Klein- REx is gratefully acknowledged. These include dedicated staff from man, L., Lee, Y.-N., Springston, S., Toniazzo, T., Krejci, R., the Chilean Weather Service (DMC), Ana Maria Cordova at Univer- Fochesatto, J., Shaw, G., Krecl, P., Brooks, B., McKeeking, G., sidad de Valparaiso, Ricardo Munoz, ˜ Jose ´ Rutllant and fellow stu- Bower, K. N., Williams, P. I., Crosier, J., Crawford, I., Con- dents at Universidad de Chile, Rosalino Fuenzalida, and fellow staff nolly, P., Covert, D., and Bandy, A. R.: Southeast Paciﬁc at- and students at Universidad Arturo Prat, Iquique, Chile; Yamina mospheric composition and variability sampled along 20 S dur- Silva at Instituto Geof´ ısico del Peru, ´ Lima and Boris Dewitte at Lab- ing VOCALS-REx, Atmos. Chem. Phys. Discuss., 11, 681–744, oratoire d’Etudes en Geoph ´ ysique et Oceanographie ´ Spatiales (LE- doi:10.5194/acpd-11-681-2011, 2011. GOS), Toulouse, France. Sounding operations were led by Tim Lim Andreae, M. O. and Merlet, P.: Emission of trace gases and aerosols and quality control by Kate Young, both of NCAR/EOL. We also from biomass burning, Global Biogeochem. Cy., 15, 955–966, thank the Natural Environment Research Council, UK, for support- ing the UK University contribution to VOCALS, and to FAAM, Di- Avey, L., Garrett, T. ., and Stohl, A.: Evaluation of the aerosol indi- rectﬂight Ltd., Avalon Engineering Ltd, and ARSF, for providing rect effect using satellite, tracer transport model, and aircraft data the BAe146 and Dornier-228 aircraft respectively. Without the un- from the International Consortium for Atmospheric Research on tiring efforts of the staff of these Facilities the science objectives Transport and Transformation,, J. Geophys. Res., 112, D10S33, of VOCALS would not have been met. The European Southern doi:10.1029/2006JD007581, 2007. Observatory (ESO) are thanked for their help and support for mea- Bennartz, R.: Global assessment of marine boundary layer cloud surements at Paranal. The NASA Langley GOES-10 analyses were droplet number concentration from satellite, J. Geophys. Res., supported by the NASA Modeling, Analysis, and Prediction Pro- 112, D02201, doi:10.1029/2006JD007547, 2007. gram and the DoE Atmospheric Radiation Measurement Program Brenguier, J.-L. and Wood, R.: Observational strategies from the Agreement DE-AI02-07ER64546. micro to meso scale, in: Perturbed clouds in the climate system, It is also a great pleasure to acknowledge the program managers in MIT Press, 2009. the US, particularly Walter Robinson from NSF and Jin Huang from Bretherton, C. S., Uttal, T., Fairall, C. W., Yuter, S. E., Weller, R. A., NOAA whose support and guidance has been invaluable through- Baumgardner, D., Comstock, K., and Wood, R.: The EPIC 2001 out. stratocumulus study, B. Am. Meteor. Soc., 85, 967–977, 2004. Funding for VOCALS-REx was provided through the following Bretherton, C. S., Wood, R., George, R. C., Leon, D., Allen, G., grants: US National Science Foundation grants OCE07-44245, and Zheng, X.: Southeast Paciﬁc stratocumulus clouds, precip- ATM-0934275, ATM0748012, ATM-0749011, ATM-0746685, itation and boundary layer structure sampled along 20 S dur- AGS-0745337, ATM-0744636, ATM-0839872, ATM-0749088, ing VOCALS-REx, Atmos. Chem. Phys., 10, 10639–10654, ATM-0745702, ATM-0745986, OCE-0744245 and OCE-0741917; doi:10.5194/acp-10-10639-2010, 2010. US National Oceanic and Atmospheric Administration grants Brioude, J., Cooper, O. R., Feingold, G., Trainer, M., Freitas, S. R., NA08OAR4320899, NA09OAR4310206, NA070AR4310282, Kowal, D., Ayers, J. K., Prins, E., Minnis, P., McKeen, S. A., NA08OAR4310597, NA08OAR4310566, and GC08-252b; Frost, G. J., and Hsie, E.-Y.: Effect of biomass burning on ma- cooperative agreements between NOAA and NSF to fund rine stratocumulus clouds off the California coast, Atmos. Chem. logistics, operations and data archiving funded through Phys., 9, 8841–8856, doi:10.5194/acp-9-8841-2009, 2009. NOAA grants NA07OAR4310267, NA06OAR4310119, and Caldwell, P., Wood, R., and Bretherton, C. S.: Mixed-layer budget NA07OAR4310248; the US Ofﬁce of Naval Research grants PE analysis of the diurnal cycle of entrainment in SE Paciﬁc stra- 0602435, N000140810437, and N000140810465; the Chilean tocumulus, J. Atmos. Sci., 62, 3775–3791, 2005. Atmos. Chem. Phys., 11, 627–654, 2011 www.atmos-chem-phys.net/11/627/2011/ R. Wood et al.: VOCALS operations 653 Chand, D., Hegg, D. A., Wood, R., Shaw, G. E., Wallace, D., pled ocean-atmosphere GCM study, J. Climate, 9, 1635–1645, and Covert, D. S.: Source attribution of climatically important 1996. aerosol properties measured at Paposo (Chile) during VOCALS, Mechoso, C. R., Robertson, A. W., Barth, N., Davey, M. K., Atmos. Chem. Phys., 10, 10789–10801, doi:10.5194/acp-10- Delecluse, P., Gent, P. 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The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and field operations

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The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and field operations

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The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and field operations

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