High-resolution subtropical summer precipitation derived from dynamical downscaling of the NCEP/DOE reanalysis: how much small-scale information is added by a regional model?
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This study assesses the regional-scale summer precipitation produced by the dynamical downscaling of analyzed large-scale fields. The main goal of this study is to investigate how much the regional model adds smaller scale precipitation information that the large-scale fields do not resolve. The modeling region for this study covers the southeastern United States (Florida, Georgia, Alabama, South Carolina, and North Carolina) where the summer climate is subtropical in nature, with a heavy influence of regional-scale convection. The coarse resolution (2.5° latitude/longitude) large-scale atmospheric variables from the National Center for Environmental Prediction (NCEP)/DOE reanalysis (R2) are downscaled using the NCEP/Environmental Climate Prediction Center regional spectral model (RSM) to produce precipitation at 20 km resolution for 16 summer seasons (1990–2005). The RSM produces realistic details in the regional summer precipitation at 20 km resolution. Compared to R2, the RSM-produced monthly precipitation shows better agreement with observations. There is a reduced wet bias and a more realistic spatial pattern of the precipitation climatology compared with the interpolated R2 values. The root mean square errors of the monthly R2 precipitation are reduced over 93% (1,697) of all the grid points in the five states (1,821). The temporal correlation also improves over 92% (1,675) of all grid points such that the domain-averaged correlation increases from 0.38 (R2) to 0.55 (RSM). The RSM accurately reproduces the first two observed eigenmodes, compared with the R2 product for which the second mode is not properly reproduced. The spatial patterns for wet versus dry summer years are also successfully simulated in RSM. For shorter time scales, the RSM resolves heavy rainfall events and their frequency better than R2. Correlation and categorical classification (above/near/below average) for the monthly frequency of heavy precipitation days is also significantly improved by the RSM.
KeywordsRoot Mean Square Error Grid Point Root Mean Square Heavy Rainfall Summer Precipitation
- Castro CL, Pielke RA Sr, Leoncini G (2005) Dynamical downscaling: assessment of value retained and added using the regional atmospheric modeling system (RAMS). J Geophys Res 110:D05108. doi: 10.1029/2004JD004721
- Diaconescu EM, Laprise R, Sushama L (2007) The impact of lateral boundary data errors on the simulated climate of a nested regional climate model. Clim Dyn 28(4). doi: 10.1007/s00382-006-0189-6
- Dickinson RE, Erroco RM, Giorgi F, Bates T (1989) A regional climate model for the western United States. Clim Change 15:383–422Google Scholar
- Fiorino M (2004) A multi-decadal daily sea surface temperature and sea ice concentration data set for the ERA-40 reanalysis. ECMWF ERA-40 Project Rep. Series 12, 16 ppGoogle Scholar
- Jolliffe IT, Stephenson DB (2003) Forecast verification: a practitioner’s guide in atmospheric science. Wiley, Hoboken, 240 ppGoogle Scholar
- Kanamitsu M, Kanamaru H, Cui Y, Juang H (2005) Parallel implementation of the regional spectral atmospheric model. PIER Project Rep. CEC-500-2005-014, 23 pp. http://www.climatechange.ca.gov/documents/pier_gcc_reports.html
- Lim YK, Cocke S, Shin DW, Schoof JT, LaRow TE, O’Brien JJ (2009) Downscaling large-scale NCEP CFS to resolve fine-scale seasonal precipitation and extremes for the crop growing seasons over the southeastern United States. Clim Dyn. doi: 10.1007/s00382-009-0671-z
- Mearns LO, Giorgi F, McDaniel L, Shields C (2003) Climate scenarios for the southeastern U.S. based on GCM and regional model simulations. Clim Change 60(1–2). doi: 10.1023/A:1026033732707
- Mearns LO, Gutowski W, Jones R, Leung R, McGinnis S, Nunes A, Qian Y (2009) A regional climate change assessment program for North America. EOS, Trans Am Geophys Union 90:311. doi: 10.1029/2009EO360002
- Rockel B, Castro CL, Pielke Sr RA, von Storch H, Leoncini G (2008) Dynamical downscaling: assessment of model system dependent retained and added variability for two different regional climate models. J Geophys Res 113:D21107. doi: 10.1029/2007JD009461
- Rossa A, Nurmi P, Ebert E (2008) Overview of methods for the verification of quantitative precipitation forecasts. In: Precipitation: advances in measurement, estimation and prediction. Springer, Berlin, pp 419–452. doi: 10.1007/978-3-540-77655-0_16
- Taylor KE, Williamson D, Zwiers F (2000) The sea surface temperature and sea-ice concentration boundary conditions of AMIP II simulations. PCMDI Rep. 60, 20 ppGoogle Scholar