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A Census of Precipitation Features in the Tropics Using TRMM: Radar, Ice Scattering, and Lightning Observations

A Census of Precipitation Features in the Tropics Using TRMM: Radar, Ice Scattering, and... An algorithm has been developed to identify precipitation features (≥≥75 km 2 in size) in two land and two ocean regions during August, September, and October 1998. It uses data from two instruments on the Tropical Rainfall Measuring Mission (TRMM) satellite: near-surface precipitation radar (PR) reflectivities, and TRMM Microwave Imager (TMI) 85.5-GHz polarization corrected temperatures (PCTs). These features were classified by size and intensity criteria to identify mesoscale convective systems (MCSs), precipitation with PCTs below 250 K, and other features without PCTs below 250 K. By using this technique, several hypotheses about the convective intensity and rainfall distributions of tropical precipitation systems can be evaluated. It was shown that features over land were much more intense than similar oceanic features as measured by their minimum PCTs, maximum heights of the 30-dB Z contour, and 6-km reflectivities. The diurnal cycle of precipitation features showed a strong afternoon maximum over land and a rather flat distribution over the ocean, quite similar to those found by others using infrared satellite techniques. Precipitation features with MCSs over the ocean contained significantly more rain outside the 250-K PCT isotherm than land systems, and in general, a significant portion (10%%––15%%) of rainfall in the Tropics falls in systems containing no PCTs less than 250 K. Volumetric rainfall and lightning characteristics (as observed by the Lightning Imaging Sensor aboard TRMM) from the systems were classified by feature intensity; similar rain amounts but highly differing lightning flash rates were found among the regions. Oceanic storms have a bimodal contribution of rainfall from two types of systems: very weak systems with little ice scattering and moderately strong systems that do not produce high lightning flash rates. Continental systems that produce the bulk of the rainfall (as sampled) are likely to have higher lightning flash rates, which are shown to be linked to stronger radar and ice-scattering intensities. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Climate American Meteorological Society

A Census of Precipitation Features in the Tropics Using TRMM: Radar, Ice Scattering, and Lightning Observations

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Publisher
American Meteorological Society
Copyright
Copyright © 1999 American Meteorological Society
ISSN
1520-0442
DOI
10.1175/1520-0442(2000)013<4087:ACOPFI>2.0.CO;2
Publisher site
See Article on Publisher Site

Abstract

An algorithm has been developed to identify precipitation features (≥≥75 km 2 in size) in two land and two ocean regions during August, September, and October 1998. It uses data from two instruments on the Tropical Rainfall Measuring Mission (TRMM) satellite: near-surface precipitation radar (PR) reflectivities, and TRMM Microwave Imager (TMI) 85.5-GHz polarization corrected temperatures (PCTs). These features were classified by size and intensity criteria to identify mesoscale convective systems (MCSs), precipitation with PCTs below 250 K, and other features without PCTs below 250 K. By using this technique, several hypotheses about the convective intensity and rainfall distributions of tropical precipitation systems can be evaluated. It was shown that features over land were much more intense than similar oceanic features as measured by their minimum PCTs, maximum heights of the 30-dB Z contour, and 6-km reflectivities. The diurnal cycle of precipitation features showed a strong afternoon maximum over land and a rather flat distribution over the ocean, quite similar to those found by others using infrared satellite techniques. Precipitation features with MCSs over the ocean contained significantly more rain outside the 250-K PCT isotherm than land systems, and in general, a significant portion (10%%––15%%) of rainfall in the Tropics falls in systems containing no PCTs less than 250 K. Volumetric rainfall and lightning characteristics (as observed by the Lightning Imaging Sensor aboard TRMM) from the systems were classified by feature intensity; similar rain amounts but highly differing lightning flash rates were found among the regions. Oceanic storms have a bimodal contribution of rainfall from two types of systems: very weak systems with little ice scattering and moderately strong systems that do not produce high lightning flash rates. Continental systems that produce the bulk of the rainfall (as sampled) are likely to have higher lightning flash rates, which are shown to be linked to stronger radar and ice-scattering intensities.

Journal

Journal of Climate – American Meteorological Society

Published: Aug 5, 1999

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