The objective of the Regional Reanalysis (RR) project is to develop a long-term set of consistent climate data at a regional scales. Given the success of NCEP’s Meso Eta Model to produce reliable water and energy cycles, a long term series of analyses prepared with a stable model and data assimilation system should have multiple uses for climate and hydrological purposes. Besides the advanced regional model, the analyses will have several additional sources of data not used in the production of the global reanalyses, like observed precipitation, clouds, and direct analysis of satellite radiances with 3DVAR. RR pilot runs at 80-km grid spacing were tested for 1998.

In order to evaluate the quality of the first guess fields of these packages, and to gain insight into the usefulness of the products in diagnostic studies involving hydrological variables in the water balance equation, a series of comparisons were performed. The products from the RR products were compared to satellite observations, Eta model operational runs and Global Reanalysis for a winter month (Jan1998) and a summer month (Jul 1998). Due to the fact that precipitation was included in the assimilation process, the RR runs were in overall better agreement with observed and satellite-estimated precipitation than the other model estimates. Excessive model forecast precipitation during summer was visible in the global reanalysis, and to a lesser degree in the operational Eta forecasts. On the other hand, the RR runs had this bias much reduced or eliminated. Similarly, a dry bias during January in all other datasets was reduced in the RR runs.

The water balance equation during July estimated from the RR products depicts a marked reduction in the magnitude of the residual with respect to the operational products. This is true even though the computation is for one month average. The results for January do not show the same measure of improvement, but this may be due to the smaller amplitude of the water cycle components during winter. Finally, the surface temperature is critical for the surface energy balance; this is another area of improvement for the regional reanalysis, since during July the surface temperature shows an increase of several degrees over Texas, which is much closer to the observations.