The Diurnal Variation of Deep Convection and Inferred Precipitation in the Central Tropical Pacific During January–February 1979

Abstract

Abstract Infrared satellite data are used to determine the diurnal variation of deep convection and inferred rainfall in the central tropical Pacific during January-February 1979. The parameter employed to characterize the convection is the percent coverage of 1.5° latitude-longitude squares by clouds with tops colder than various specified equivalent blackbody temperatures. Rainfall estimates are based on an empirical relationship between precipitation rate and fractional coverage by cold clouds derived from measurements taken during the GARP Atlantic Tropical Experiment (GATE). In addition, the diurnal variation of vertical motion, determined kinematically from level III-b gridded wind analyses of the European Centre for Medium Range Weather Forecasts, is examined. Principal conclusions are: A pronounced diurnal variation of deep convection occurred throughout the region of study. At certain hours fractional coverage by clouds colder than −36°C deviated by as much as 40% from the daily mean. The variati...