In the NCEP global forecasts (MRF), the initial soil moisture is based on the previously forecasted precipitation and evaporation. A positive precipitation-soil moisture feedback, however, can amplify errors in the forecast precipitation. Consequently the NCEP/DOE Reanalysis, (R-2, Kanamitsu et al, 2000; Ebisuzaki et al, 1999) used observed precipitation to drive the soil moisture. This and other changes resulted in R-2's soil moisture having more realistic variability (compared with Illinois measurements) than the earlier NCEP/NCAR Reanalysis (Kalnay et al, 1996), which used forecast precipitation as the current operational system.

In this study, we will examine the effects of the R-2 soil moisture on the longer lead forecasts (up to 30 days). To be consistent with the R-2 soil moisture, we will be using the R-2 analyses and R-2 model. The latter is a T62 version of the MRF. We will be emphasizing soil moisture effects on the forecasts in the Northern hemisphere warm season.

Kalnay, E. et al., 1996: The NCEP/NCAR 40 Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77, 437-471.

Kanamitsu, M., W. Ebisuzaki, J. Woolen, J. Potter, and M. Fiorino, 2000: An overview of NCEP/DOE Reanalysis-2. Proc. 2nd Intl. Conf. On Reanalyses, Reading, England, 23-27 Aug. 1999. WCRP-109 (WMO/TD-985) WMO, Geneva, 1-4.

Ebisuzaki, W., M. Kanamitsu, J. Potter, M. Fiorino, 1999: An Overview of Reanalysis-2, Proceedings of the 23rd Annual Climate Diagnostics Workshop, Miami, Florida (Oct 26-30, 1998), 119-122.