Surface water and energy budgets in the NCEP regional spectral model

Abstract

Characteristics of the U.S. surface water and energy budgets in the National Centers for Environmental Prediction (NCEP) regional spectral model (RSM) and the driving NCEP/NCAR (NCEPR) reanalysis are compared. The RSM is similar to the global spectral model (GSM) used in the reanalyses except that it has higher resolution over a limited area. There are, however, other important differences. Besides minor parameterization differences the RSM does not have an artificial water source to maintain the surface moisture (unlike the NCEPR), and the RSM surface water dries. Although the much larger wintertime surface water difference has only a small effect on the evaporation differences and other components of the wintertime water and energy cycles, summertime effects are greater. Relative to the NCEPR the RSM develops a consistent summertime pattern of decreased surface water, precipitation, evaporation, increased sensible heating, outgoing longwave radiation, incoming solar radiation and temperature over the western Mississippi River basin and the Gulf of Mexico, south and eastern coasts. Opposite features occur over the eastern Mississippi River basin and the U.S. West in the RSM. These hydrologically and energetically consistent RSM and NCEPR spatial differences extend to interannual variations in RSM water and energy budgets, which appear to be more strongly influenced by larger interannual surface water variations than might be discerned from the NCEPR.