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Downscaling with a nested regional climate model in near‐surface fields over the contiguous United States
Author(s) -
Wang Jiali,
Kotamarthi Veerabhadra R.
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2014jd021696
Subject(s) - downscaling , weather research and forecasting model , climatology , precipitation , environmental science , climate model , meteorology , atmospheric model , nested set model , climate change , atmospheric sciences , geography , geology , computer science , oceanography , database , relational database
The Weather Research and Forecasting (WRF) model is used for dynamic downscaling of 2.5‐degree National Centers for Environmental Prediction‐U.S. Department of Energy Reanalysis II (NCEP‐R2) data for 1980–2010 at 12 km resolution over most of North America. The model's performance for surface air temperature and precipitation is evaluated by comparison with high‐resolution observational data sets. The model's ability to add value is investigated by comparison with NCEP‐R2 data and a 50 km regional climate simulation. The causes for major model bias are studied through additional sensitivity experiments with various model setup/integration approaches and physics representations. The WRF captures the main features of the spatial patterns and annual cycles of air temperature and precipitation over most of the contiguous United States. However, simulated air temperatures over the south central region and precipitation over the Great Plains and the Southwest have significant biases. Allowing longer spin‐up time, reducing the nudging strength, or replacing the WRF Single‐Moment six‐class microphysics with Morrison microphysics reduces the bias over some subregions. However, replacing the Grell‐Devenyi cumulus parameterization with Kain‐Fritsch shows no improvement. The 12 km simulation does add value above the NCEP‐R2 data and the 50 km simulation over mountainous and coastal zones.