A comparison of the statistics of daily precipitation over the conterminous United States and South America is carried out using gridded station data, and three generations of reanalysis products in use at the National Centers for Environmental Prediction (NCEP). The reanalysis products are the NCEP/NCAR Reanalysis (Kalnay et al. 1996), the NCEP/DOE Reanalysis (Kanamitsu et al. 2002), and the NCEP Climate Forecast System (CFS) Reanalysis (Saha et al. 2010). Several simple measures are used to characterize relationships between the observations and the reanalysis products, including bias, precipitation probability, variance, and correlation.

It is shown that the CFS Reanalysis represents a clear improvement over the earlier reanalysis products, though significant biases remain. Comparisons of the error patterns in the reanalysis products provide a suitable basis for confident conversion of the Climate Prediction Center (CPC) operational monitoring and prediction products to the new generation of analyses based on CFS.