Precipitation Intensity Spectrum Analysis for Regional Climate Model Simulations over the Central United States

Trends in extreme precipitation frequency were evaluated for RegCM4.4 nested regional climate model simulations over the CORDEX-North American Domain with 50 and 25 kilometer grid spacings and three different convection schemes. HadGEM2-ES and GFDL-ESM2M AOGCMs (for RCP8.5 emissions scenarios) were used for the initial and lateral boundary conditions to simulate present and future climate (1951-2098).

We replicated findings from Groisman et al. (2012) in the RegCM4.4 model runs, although results vary due to differences caused by convection schemes and lateral boundary conditions. To gain further insight into these extreme precipitation events we are analyzing the precipitation intensity spectrum. From previous analysis using fixed thresholds, there are indications of increased frequency of extreme precipitation events in the recent past and a greater increase in frequency for the warm season precipitation events. We examine precipitation intensity spectrum for both entire year records throughout the time period and the warm and cold season months of these same years. Results are compared to the precipitation intensity spectrum from daily rain gauge data to evaluate the accuracy of these extreme precipitation events.