Changing characteristics of extreme precipitation over tropical ocean and land in warmer climates

 

Prof. William K. M. Lau 

University of Maryland, USA

 

邀請人/報告會主持人 ： 吳國雄 院士

 

2023年8月4日（星期五）15:00

3號樓第三會議室

 

報告摘要:

In this talk, results are reported on the changing nature of tropical climatic extreme precipitation-cloud regimes based on Atmospheric Model Intercomparison Project (AMIP)-type simulations driven by a) uniform global SST increase by 4K (P4K), and b) SST anomalies derived from CMIP6 coupled models, forced by 4xCO2 radiative forcing. We find that as the surface warms, there is increasing fractional contribution of stratiform rain as a function of precipitation intensity, with the most extreme but rare events occurring preferentially over land more than ocean. Extreme precipitation is facilitated by increased precipitation efficiency, reflecting accelerated rates of recycling of precipitation-cloud water.  Changes in vertical profiles of clouds, condensation heating and vertical motions indicate that large-scale surface warming of the ocean (P4K) is the primary cause contributing to organization structure resembling the well-known Mesoscale Convective System (MCS) for increased extreme precipitation on hourly and daily time scales. Additional 4xCO2 atmospheric radiative heating, and dynamically consistent anomalous SSTA further amplify the MCS organization.  Analyses of the surface moist static energy and relative humidity distributions show that rare “record-breaking” precipitation events tend to occur over land due to convective inhibition (CIN), resulting in delaying triggering of deep convection, and releasing of surplus stored CAPE stored during CIN.  

 

報告人簡介:

William K. M. Lau received his B. Sc. (Mathematics and Physics) in 1972, and B. Sc. Special (Applied Mathematics) in 1973 from University of Hong Kong, his PhD in Atmospheric Sciences in 1978, from the University of Washington, Seattle, Washington, U.S.  He was assistant professor at the Naval Postgraduate School (1978-1980) before joining the NASA Goddard Space Flight Center (GSFC) in 1981.  He served as the Head of the Climate and Radiation Branch (1991-2000), Chief, the Laboratory for Atmospheres (2001-2010), and the Deputy Director for Science, Earth Science Division, NASA/GSFC (2011-2014).  Currently, Dr. Lau is a senior scientist at the Earth System Science Interdisciplinary Center (ESSIC), and adjunct professor of the Department of Atmospheric and Oceanic Sciences, University of Maryland. His research spans over 4 decades covering a wide range of topics in climate dynamics, tropical and monsoon meteorology, ocean-atmosphere interaction, aerosol-water cycle interaction, climate variability and change. Over the years, Dr. Lau frequently visited international research and academic institutions in Southeast Asia, North and South America, and Europe presenting invited lectures, and keynote speeches in scientific meetings to promote research collaboration and awareness in regional impacts of climate variability and change.