Physical Processes that determine Daily Extreme Precipitation over Southern Alaska given by CMIP5 GCMs Using SOMs

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Sunday, 2 February 2014
Hall C3 (The Georgia World Congress Center )
Kevin Smalley, Iowa State University, Ames, IA; and W. Gutowski

Self Organizing Maps (SOMs) in conjunction with Phase 5 of the Coupled Model Intercomparison Project (CMIP5) Global Climate Models (GCMs) will be used to better understand physical processes leading to daily extreme precipitation events in Southern Alaska from 1986 - 2005. GCMs have been scaled to 0.56 degree spatial resolution, or the spatial resolution of the MIROC4h, in order to define a widespread extreme daily precipitation event for individual models. Thus, widespread daily extreme precipitation events easily are compared between different models; with a widespread extreme being as the top 1% of daily precipitation occurring on at least 50 grid points. The CMIP5 models and observations are then regridded to a 0.5 degree common grid. Thus considering GCMs are coarser in spatial resolution, a common grid effectively creates clarity in determining the physical processes that lead to daily extreme precipitation. The Master SOM is then created through mapping the synoptic circulation depicted by each model. Widespread extremes are then mapped onto the Master SOM. This analysis technique allows for the differentiation of large-scale circulations conducive for extreme events, and the physical processes that lead to them. Two main questions that will be addressed by this research are: 1) What are the most important physical processes leading to extreme daily precipitation in the Arctic? 2) How do the models predict these physical processes leading to extreme precipitation? Courser GCMs are not able to detect small scale physical processes leading to extreme events. Leading to a hypothesis of, CMIP5 GCMs with higher spatial resolution will better depict physical processes leading to widespread extreme daily precipitation events in southern Alaska.