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Understanding the Importance of Microphysics and Macrophysics for Warm Rain in Marine Low Clouds. Part I: Satellite Observations

Understanding the Importance of Microphysics and Macrophysics for Warm Rain in Marine Low Clouds.... The importance of macrophysical variables cloud thickness, liquid water path (LWP) and microphysical variables (effective radius r e , effective droplet concentration N eff ) on warm drizzle intensity and frequency across the tropics and subtropics is studied. In this first part of a two-part study, Moderate Resolution Imaging Spectroradiometer (MODIS) optical and CloudSat cloud radar data are used to understand warm rain in marine clouds. Part II uses simple heuristic models. Cloud-top height and LWP substantially increase as drizzle intensity increases. Droplet radius estimated from MODIS also increases with cloud radar reflectivity (dB Z ) but levels off as dB Z > 0, except where the influence of continental pollution is present, in which case a monotonic increase of r e with drizzle intensity occurs. Off the Asian coast and over the Gulf of Mexico, r e values are smaller (by several μ m) and N eff values are larger compared to more remote marine regions. For heavy drizzle intensity, both r e and N eff values off the Asian coast and over the Gulf of Mexico approach r e and N eff values in more remote marine regions. Drizzle frequency , defined as profiles in which maximum dB Z > −15, increases dramatically and nearly uniformly when cloud tops grow from 1 to 2 km. Drizzle frequencies exceed 90% in all regions when LWPs exceed 250 g m −2 and N eff values are below 50 cm −3 , even in regions where drizzle occurs infrequently on the whole. The fact that the relationship among drizzle frequency, LWP, and N eff is essentially the same for all regions suggests a near universality among tropical and subtropical regions. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of the Atmospheric Sciences American Meteorological Society

Understanding the Importance of Microphysics and Macrophysics for Warm Rain in Marine Low Clouds. Part I: Satellite Observations

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Publisher
American Meteorological Society
Copyright
Copyright © 2009 American Meteorological Society
ISSN
1520-0469
DOI
10.1175/2009JAS3071.1
Publisher site
See Article on Publisher Site

Abstract

The importance of macrophysical variables cloud thickness, liquid water path (LWP) and microphysical variables (effective radius r e , effective droplet concentration N eff ) on warm drizzle intensity and frequency across the tropics and subtropics is studied. In this first part of a two-part study, Moderate Resolution Imaging Spectroradiometer (MODIS) optical and CloudSat cloud radar data are used to understand warm rain in marine clouds. Part II uses simple heuristic models. Cloud-top height and LWP substantially increase as drizzle intensity increases. Droplet radius estimated from MODIS also increases with cloud radar reflectivity (dB Z ) but levels off as dB Z > 0, except where the influence of continental pollution is present, in which case a monotonic increase of r e with drizzle intensity occurs. Off the Asian coast and over the Gulf of Mexico, r e values are smaller (by several μ m) and N eff values are larger compared to more remote marine regions. For heavy drizzle intensity, both r e and N eff values off the Asian coast and over the Gulf of Mexico approach r e and N eff values in more remote marine regions. Drizzle frequency , defined as profiles in which maximum dB Z > −15, increases dramatically and nearly uniformly when cloud tops grow from 1 to 2 km. Drizzle frequencies exceed 90% in all regions when LWPs exceed 250 g m −2 and N eff values are below 50 cm −3 , even in regions where drizzle occurs infrequently on the whole. The fact that the relationship among drizzle frequency, LWP, and N eff is essentially the same for all regions suggests a near universality among tropical and subtropical regions.

Journal

Journal of the Atmospheric Sciences – American Meteorological Society

Published: Jan 9, 2009

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