Evaluation of precipitation variability over northern South America based on CMIP5 historical model simulations

Abstract:

Northern South America is identified as one of the most vulnerable regions to be affected by climate change. Furthermore, recent extreme wet seasons over the region have caused diverse socio-economic consequences. Hence, the evaluation of the representation of local climate of rainfall simulations at intra-annual seasonal and inter-annual time scales by the CMIP5 models is urgently required, in order to identify and analyze projections of regional and local climate under a global climate change scenario. Here, we evaluate the ability of seven of the CMIP5 models (selected based on literature review) to represent the seasonal mean precipitation and its inter-annual variability over northern South America. Our results suggest that it is easier for models to reproduce rainfall distribution during boreal summer and fall over both oceans and land, since during these seasons, not only incoming radiation, but also ocean-atmosphere feedbacks over Atlantic and Pacific oceans, locate the ITCZ on the Northern Hemisphere. Conversely, models exhibit the worse simulations of the seasonal mean precipitation during boreal winter and spring, when these processes have opposite effects locating the ITCZ. Our results suggest that the models with a better representation of the oceanic ITCZ and the local low-level jets over northern South America, such as the Choco low-level jet, are able to realistically simulate the main features of seasonal precipitation pattern over northern South America.