Review of Recent Climate Conditions and Forecasts
Abstract

Abstract Author: V. E. Kousky, V. B. S. Silva, and R. W. Higgins

Abstract Title: Intercomparison of Daily Precipitation Statistics for the United States in Observations, the NCEP/NCAR Reanalysis, and the NCEP/DOE Reanalysis

Abstract: An intercomparison of the statistics of daily precipitation within seasonal climate over the conterminous United States is carried out using gridded station data, the NCEP/NCAR Reanalysis (referred to as R1; Kalnay et al. 1996) and a follow-on NCEP/DOE Reanalysis that uses an updated forecast model and data assimilation system (referred to as R2; Kanamitsu et al. 2002). Differences in the occurrence and intensity of daily precipitation between the observations and the reanalysis products are examined, with emphasis on the frequencies of wet and dry spells in each product. These comparisons expose details of the regional and seasonal dependence of the bias in the reanalysis products over the conterminous United States. The comparison also motivates additional synoptic studies aimed at improved understanding of the linkage between daily precipitation and related circulation features.

These comparisons are carried out in advance of a comprehensive evaluation of a new reanalysis product under development at NCEP using the coupled Climate Forecast System (CFSR, Saha et al 2008). If the evaluation reveals that CFSR is an improvement over R1 and R2, then CFSR will replace R1 and R2 in CPC operational real-time monitoring activities. Thus, a comprehensive evaluation of the quality of daily precipitation statistics in R1 and R2 is an important first step in advance of the comparison to CFSR.

Kalnay, E., and co-authors 1996: The NMC.NCAR Reanalysis Project, Bull. Amer. Meteor. Soc., 77, 437-471.

Kanamitsu, M, W. Ebisuzaki, J. Woollen,S.-K. Yang, J. J. Hnilo , M. Fiorino , and G. L. Potter: The NCEP-DOE AMIP-II Reanalysis (R2), 2002: Bull Amer.Met.Soc, 83, 1631-1643