Comparing nudging techniques with increasing horizontal resolution in regional climate models

The WRF model is used as a regional climate model to downscale outputs from the CCSM3 global climate model forced by the A1B future emissions scenario from IPCC-AR4. Using a tool that creates WPS intermediate files for ICs and BCs into WRF, CCSM 6-hourly outputs are downscaled to 108, 36, and 12 km resolutions for two climate periods consisting of the years 2001-2003 and 2048-2050. In one set of simulations, WRF utilizes analysis nudging of the GCM in the outermost 108 km domain, while in another set of simulations spectral nudging is applied to all three domains.

We employ a hybrid airmass classification scheme called the Spatial Synoptic Classification (SSC) which uses surface parameters to assign daily weather type classifications for any particular point. The SSC is run for all three WRF resolutions, as well as the CCSM itself, for the two climate periods. We explore the impact of increasing horizontal grid resolution and different nudging techniques on the airmass classifications at various locations in the modeling domain.