Geographical and seasonal distribution of tropical tropopause thin clouds and their relation to deep convection and water vapor viewed from satellite measurements

Abstract

The climatologies of deep convection, thin clouds, and water vapor measurements from four independent satellites are compared in this study. Deep convection reaching the tropical tropopause layer (TTL) is indicated by the area of the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) 20 dBZ reflectivity reaching 14 km and the area of the TRMM visible and infrared scanner (VIRS) brightness temperature at 10.8 μm (TB11) < 210 K. TTL clouds are identified by 17 years of Stratospheric Aerosol and Gas Experiment (SAGE) II measurements and by 1 year of Earth Observing System (EOS) Microwave Limb Sounder (MLS) ice water content in 2005. TTL water vapor is estimated from 2005 EOS MLS retrievals. Results suggest that TTL clouds are geographically and seasonally correlated with deep convection as inferred from the area of TB11 < 210 K. Patterns of regional differences of seasonal variations of deep convection are also related to the regional differences of seasonal variations of TTL clouds. By grouping the Ice Cloud and Land Elevation Satellite/Geoscience Laser Altimeter System (ICESat/GLAS) layer cloud products, we find that there is a general spatial correlation between the largest, thickest TTL layer clouds with the highest optical depth and the regions with the most intense deep convection. MLS CO and water vapor at 146 hPa have similar geographical and seasonal variations as deep convection and TTL clouds. EOS MLS 100 hPa water vapor is low over the west Pacific Ocean at the same location and time as more TTL clouds are observed.