Assessment of Precipitation Simulation by NARCCAP Regional Climate Models and the Relationship with Large-Scale Circulation Bias

It is known that climate change is likely to have many effects on nature and society. To investigate the uncertainties in regional-scale climate projections of future climate the North American Regional Climate Change Assessment Program (NARCCAP) produced high resolution climate change simulations. Given the desire to use this dataset for impact assessments and the lack of the comparison between its different model outputs, the goal of this research is to assess the precipitation simulation by NARCCAP regional climate models and to figure out some questions. Are certain RCM model outputs more appropriate for assessing the precipitation in some certain regional areas?  Why the models do well in some regions and less well in others? The research comparing the Stage IV precipitation data and NCEP-DOE Reanalysis2 data with simulation results suggests that nudging RCMs in NARCCAP tend to have better ability in capturing the large-scale circulation than the non-nudging ones, which is very important for the simulation of precipitation. It is shown that the non-nudging group produce much intense dry bias in the great plain areas, which very likely due to its simulation of weaker Low level jet and negative bias in low level humidity.  These analyses can help us better understand the sources of errors in the regional climate models.