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.[1] From analysis of TRMM data, we find that warm rain accounts for 31% of the total rain amount and 72% of the total rain area in the tropics, and plays an important role in regulating the moisture content of the tropical atmosphere. There is a substantial increase in precipitation efficiency of light warm rain as the sea surface temperature increases, but precipitation efficiency of heavy rain associated with deep convection is independent of sea surface temperature. This implies that in a warmer climate, there may be more warm rain, at the expense of less cloud water available for middle and high level clouds.

[1] In this study, we find from analyses of projections of 14 CMIP5 models a robust, canonical global response in rainfall characteristics to a warming climate. Under a scenario of 1% increase per year of CO 2 emission, the model ensemble projects globally more heavy precipitation (+7 AE 2.4%K À1 ), less moderate precipitation (À2.5 AE 0.6% K À1 ), more light precipitation (+1.8 AE 1.3%K À1 ), and increased length of dry (no-rain) periods (+4.7 AE 2.1%K À1 ). Regionally, a majority of the models project a consistent response with more heavy precipitation over climatologically wet regions of the deep tropics, especially the equatorial Pacific Ocean and the Asian monsoon regions, and more dry periods over the land areas of the subtropics and the tropical marginal convective zones. Our results suggest that increased CO 2 emissions induce a global adjustment in circulation and moisture availability manifested in basic changes in global precipitation characteristics, including increasing risks of severe floods and droughts in preferred geographic locations worldwide. Citation: Lau, W. K.-M., H.-T. Wu, and K.-M. Kim (2013), A canonical response of precipitation characteristics to global warming from CMIP5 models,

Abstract:Analyses of two state-of-the-art, blended space-based and ground-based global rainfall data sets from the Global Precipitation Climatology Project (GPCP) and the Climate Prediction Center Merged Analysis Product (CMAP) reveal that there was a significant shift in the probability distribution functions of tropical rainfall during the period 1979-2003. This shift features a positive trend in the occurrence of heavy (top 10% by rain amount) and light (bottom 5%) rain events in the tropics during 1979-2003 and a negative trend in moderate (25-75%) rain events. These trends are consistent in both data sets and are in overall agreement with the Climate Research Unit's (CRU) gauge-only rainfall data over land. The relationships among the trends and the possible long-term changes in rainfall characteristics are discussed. Published in