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Advanced Taiwan Ocean Prediction System

Tseng, Tsu-Lun - ALL News | 2018-08-22 | Count:217


Title: Understanding Rainfall and Circulation Changes under Global Warming: The Role of Ocean


As the climate warms, most of the global climate models project more wettening in the climatological wet region and more drying in the climatological dry region. The so-called “wet-gets-wetter” phenomenon is related with the thermodynamic theory of increasing water vapor in a warmer atmosphere. On the other hand, some changes in rainfall patterns associated with changes of circulation are expected. In this talk, we will discuss two of the robust features of precipitation pattern changes projected by global climate models: (1) the tropical rain belt shifting toward the equator (2) more significant drying trend in the Southern Hemisphere comparing with the Northern Hemisphere. Through analyzing outputs from Coupled Model Intercomparison Project Phase 5 (CMIP5) and performing idealized experiments, we will show that the former is related with less evaporated cooling and enhanced warming at the equatorial region, and the later is associated with more significant warming trend in the Northern Hemisphere comparing to the Southern Hemisphere. Both features could be traced back to the climatological oceanic circulation – the equatorial cold tongue inhibits evaporation and climatological upwelling in the Southern Ocean slows down surface warming – shedding lights on predictability. We will end the talk by demonstrating the diverse transient evolutions of the two patterns, using the historical and RCP8.5 scenario CESM large ensemble simulations. The results further emphasize the complex temporal evolution of tropical precipitation patterns originated from the nonlinearity of high latitude ocean.


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