Climatology and changes in tropical oceanic rainfall characteristics inferred from Tropical Rainfall Measuring Mission (TRMM) data (1998–2009)

Abstract

[1] This study investigates the climatological and changing characteristics of tropical rain and cloud systems in relation to sea surface temperature (SST) changes using Tropical Rainfall Measuring Mission (TRMM) data (1998–2009). Rainfall and cloud characteristics are determined from probability distribution functions (pdf), derived from daily TRMM Microwave Imager (TMI) and Precipitation Radar (PR) surface rain, Visible and Infrared Scanner (VIRS) brightness temperature (Tb), and PR echo top height (HET). Results show that the top 10% heavy rain is associated with cold cloud tops (Tb 6 km), associated with ice phase rain in the Intertropical Convergence Zone and monsoon regions. The bottom 5% light rain occurs most frequently in the subtropics and also in the warm pool regions with low cloud top (Tb > 273 K) and HET ∼ 1–4 km. Intermediate rain (25th to 75th percentile) is contributed by a wide range of middle clouds and mixed-phase rain centered at Tb ∼ 230–260 K and HET ∼ 4–6 km within the warm pool. The relationships between rainfall and SST depend strongly on rain types. We find that a warmer tropical ocean favors a large increase in annual heavy rain accumulation, a mild reduction in light to moderate rain, and a slight increase in extremely light rain. The annual accumulation of extreme heavy rain increases approximately 80%–90% for every degree rise in SST, much higher than that expected from the Clausius-Clapeyron equation for global water balance. This is possibly because heavy rain is only a component of the tropical water cycle and is strongly associated with ice phase processes and convective dynamics feedback.