P2.92 Changes of tropical rain and associated Precipitation efficiency in tropical oceans in response to climate warming

Thursday, 13 May 2010
Arizona Ballroom 7 (JW MArriott Starr Pass Resort)
Chung-Hsiung Sui, National Taiwan Univ., Taipei, Taiwan

Studies using rainfall station data in various regions and merged satellite rain over tropical oceans found a shift of rainfall frequency distribution with climate warming. Because of the regional differences in the spectral rainfall changes found by these studies, and uncertainties in rainfall estimate, especially over oceans, we need to analyze these different data sources in a consistent way along with satellite measurements to address some obvious questions about the rainfall spectral changes, namely, whether the changes show any consistent trends ? if the changes are regime dependent, what are the responsible environmental factors? like land surface vs oceanic surface, broadscale ascending vs descending motion ? aerosol effect ? In addition, such features also need to be interpreted. In the recent study, we address the problem about how convection, warm and deep clouds/rain change in response to climate warming. We discuss the problem through an analysis of precipitation efficiency (PE) as a function of SST in different regimes of rainrate and ascending motion, and find that PE increases more significantly with increasing SST in strong ascending regime. Based on this result along with relevant studies, we are working to substantiate a working hypothesis that a warming climate leads to more frequent heavy rain events (i.e. higher precipitation efficiency for heavier rain) with strong updrafts that drive the compensating subsidence, through broad-scale overturning circulation. The broad-scale subsidence regulated by radiative cooling controls the intermediate and light raining events.
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