An evaluation of dynamical downscaling of Central Plains summer precipitation using a WRF‐based regional climate model at a convection‐permitting 4 km resolution. Issue 23 (2nd December 2016)

• Record Type: Journal Article
• Authors: Sun, Xuguang; Xue, Ming; Brotzge, Jerald; McPherson, Renee A.; Hu, Xiao‐Ming; Yang, Xiu‐Qun
• Is Part Of: Journal of geophysical research. Volume 121:Issue 23(2016)
• Page Start: 13, 801
• Page End: 13, 825
• Publication Date: 2016-12-02
• Subjects: dynamical downscaling -- regional climate simulation -- convection‐permitting resolution -- Great Plains MJJA precipitation -- low‐level jet; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2016JD024796
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: A significant challenge with dynamical downscaling of climate simulations is the ability to accurately represent convection and precipitation. The use of convection‐permitting resolutions avoids cumulus parameterization, which is known to be a large source of uncertainty. A regional climate model (RCM) based on the Weather Research and Forecasting model is configured with a 4 km grid spacing and applied to the U.S. Great Plains, a region characterized by many forms of weather and climate extremes. The 4 km RCM is evaluated by running it in a hindcast mode over the central U.S. region for a 10 year period, forced at the boundary by the 32 km North America Regional Reanalysis. The model is also run at a 25 km grid spacing, but with cumulus parameterization turned on for comparison. The 4 km run more successfully reproduces certain observed features of the Great Plains May‐through‐August precipitation. In particular, the magnitude of extreme precipitation and the diurnal cycle of precipitation over the Great Plains are better simulated. The 4 km run more realistically simulates the low‐level jet and related atmospheric circulations that transport and redistribute moisture from Gulf of Mexico. The convection‐permitting RCM may therefore produce better dynamical downscaling of future climate when nested within global model climate projections, especially for extreme precipitation magnitudes. The 4 km and 25 km simulations do share similar precipitation biases, including low biases over the central Great Plains and high biases over the Rockies. These biases appear linked to circulation biases in the simulations, but determining of the exact causes will require extensive, separate studies. Key Points: Ten‐year regional climate simulations at convection‐permitting 4 km and convection‐parameterizing 25 km grid spacings are performed The 4 km simulation better reproduced the magnitude of extreme precipitation, the diurnal cycle of precipitation, and the Great Plains LLJ Both simulations have similar precipitation low bias over the Great Plains and high bias over the Rockies consistent with circulation bias