21st Century Precipitation Extremes in the CMIP5 Climate Projections

Grid-based daily and sub-daily precipitation from multiple Global Climate Models (GCMs) from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) are used to assess the changes in precipitation extremes over the 21st century. Our study covers 1960-2005 in the historical period and 2010-2100 in the future period under the Representative Concentration Pathway (RCP) 8.5. We perform extreme value analysis by fitting a Generalized Extreme Value (GEV) distribution on annual maximum precipitation under several durations (from 3 to 240 hours) and by finding rainfall quantiles of low exceedance probabilities. Subsequently, regional intensity-duration-frequency (IDF) curves are plotted for both historic and future periods for several return periods to understand the changing relationship among the different characteristics of precipitation extremes. We analyze the performance of the GCMs through comparison to observational-based dataset in the historical period, and also assess the changes of these extremes in the future period. A statistical bias-correction technique that uses quantile-mapping is then applied to the GCMs precipitation data and we assess the improvement in precipitation extreme simulation. Additionally, we test the robustness of the future change across the GCMs, and before and after bias-correction, by quantifying the uncertainty in the simulation of wet extremes. Overall, this study informs the effort to correctly use GCM data in simulating extremes and provides an outlook of these extremes in the future.