The Relationship of Sea Surface Temperature and Water Vapor Amount to Convection over the Western Tropical Pacific Revealed from Split Window Measurements

[摘要] The local associations between convective activity and sea surface temperature (SST), and also water vapor amount have been investigated over the western tropical Pacific using split window data (11μm, 12μm) from the NOAA-7 Advanced Very High Resolution Radiometer (AVHRR) for the period September 1983 to August 1984. SST and indices of convective activity and water vapor amount are all estimated from the split window data. Monthly means of each variable, determined over 2.5°×2.5°latitude-longitude areas, are used for this study.It is revealed that the mean depth of convection is mostly correlated with water vapor amount while convection becomes more active with the increase of both SST and water vapor amount. The convection is slightly dependent on SST for a fixed water vapor amount, while convective activity is highly related with the increase of water vapor amount at a specific SST. Deep convection areas coincide with larger amounts of water vapor rather than warmer SSTs, and convectively suppressed areas over warmer SST areas are found to have smaller amounts of water vapor.For the same SST and water vapor amount, the convection over region I (20°N-Equator, 130°E170°W) where the intertropical convergence zone (ITCZ) is dominant, is less deep than that over region II (Eq.-20°S, 150°E-170°W) where the south Pacific convergence zone (SPCZ) prevails. Deep convection (cloud tops higher than 10 km) occurs over region I when the brightness temperature difference of the split window data is greater than 2.1°C(2.0°C over region II) and the SST warmer than 28.2°C(27.2°C over region II).

[学科分类] 大气科学