Satellite Observed Atmospheric Variability over the Life Cycle of Tropical Convective Systems

In this study the dynamic and thermodynamic variability associated with tropical convective development is explored from satellite observations. While convective clouds are detected by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR), environmental parameters such as atmospheric temperature and moisture are obtained from Aqua Atmospheric Infrared Sounder (AIRS) and other sun-synchronous satellite instruments. The environmental parameters are projected onto a temporal sequence composited with respect to the lag in local overpass time before or after the TRMM detects convection. Such a compositing technique allows one to statistically examine the evolution of ambient dynamic and thermodynamic perturbations toward and following the convective occurrence.

Notable findings include 1) a systematic moisture increase in the free troposphere and an abrupt ventilation of the atmospheric boundary layer are evident in association with deep convection, 2) a bipolar temperature anomaly with a lower tropospheric cooling and an upper tropospheric warming emerges as convection develops, and 3) the ratio of precipitation to the moisture source (moisture convergence plus surface evaporation) stays nearly constant around 0.8 during convection is developing, while the ratio begins to vary and diverge as the convection matures and decays. This paper will outline these findings and conduct a simple thermodynamic budget analysis to discuss the physical implications for the interactions between convection and the large-scale environment.