Modulation of Precipitation under Future Warm Climate over the CONUS

Extreme precipitation intensities have increased in all regions of the Contiguous United States (CONUS) and are expected to further increase with warming at scaling rates of about 7% per degree Celsius. This increase in precipitation intensities could significantly increase flash flood hazards due to climate change.

In the present work, we use the Pseudo Global Warming (PGW) method to create forcing data representative of the future climate of 2070-2090 period (under RCP8.5) scenario. A current climate simulation for the ten-year period (2005-2014) is performed using forcing data from Global Forecast System (GFS). We perturb the lateral boundary conditions of GFS data with high-end scenario (RCP8.5) CCSM4 data (http://rda.ucar.edu/datasets/ds316.1/). The PGW method, in combination with spectral nudging, avoids the introduction of internal climate variability that could otherwise substantially influence climate change analyses of decadal-long simulations, but still allows the model to adjust for potential inconsistencies from domain internal climate change forcing.

We perform all simulations with the Weather Research and Forecasting (WRF) model using a horizontal grid spacing of 12 km over CONUS. The WRF capability will be extended to include a sophisticated land surface model, Noah-MP, which has been demonstrated to significantly improve the simulation of atmosphere-surface interaction when compared to existing land surface models. The modulation of precipitation over CONUS from the current climate to the future climate time periods is analyzed and presented.