The Environmental Fluid Dynamics Lecture Series Presents a Seminar

1. The Environmental Fluid Dynamics Lecture Series Presents a Seminar Dr. V. RaoKotamarthi Head, Climate Research Station Environmental Science Division Argonne National Laboratory Tuesday, March 4 Dean’s Boardroom, 258 Fitzpatrick 11am-12noon Does Improving Model Resolution Lead to Higher Fidelity Climate Simulations? Evaluation of regional scale climate models is aimed at testing the ability of the model for capturing regional and local phenomena on climate scales. Climate variability on smaller spatial and temporal scales is a primary target, followed by extreme event climatology in space and time. Model simulations from 1980 to 2010 over a domain that covers much of North America (600 × 516 grid cells over longitude and latitude) at 12 km resolution using the Nested Regional Climate Model (WRF V3.3.1) were used as one of our regional climate models (RCMs) and observational data included PRISM monthly dataset, CPC daily dataset, as well as NARR 3 hourly dataset. The effects of high-resolution on the ability of the model were investigated through comparison with North American Regional Climate Change Program (NARCCAP) 50-km results and NCEP-R2. The causes for major model biases were studied through supplementary sensitivity experiments with various physics representations, nudging approaches, and spin-up times. Comparison with the NARCCAP results showed that the NRCM improved downscaling skills for the geographic distribution and seasonal variation of air temperature over all the subregions except the South Central (SC), and of precipitation over all the subregions except the Great Plains (GP). The NRCM also showed better downscaling skill in simulating the probability distribution function of daily precipitation and temperature, with stronger similarity to the observation than the NARCCAP. The NRCM generates a slow diurnal propagation and a persistent rainfall system over GP in the warm season. Shortening the nudging duration and allowing longer spin-up time can partly address this problem, and weakening nudging strength was also helpful.