NCEP/NCAR reanalysis and the use of satellite data

The impact of satellite data on atmospheric analysis was examined using the NCEP/NCAR reanalysis system. Focus was placed on satellite temperature retrievals, cloud motion vectors, sea surface temperature (SST) analysis and direct use of radiances. Several experimental one-month analyses were produced and compared with the corresponding control analyses. The satellite data was very important for analyses over extreme data sparse areas over eastern Oceans in the Southern Hemisphere and in the stratosphere. Fortunately, current analysis systems effectively utilized available observations so that reasonably accurate analyses could be obtained in most of the Southern Hemisphere without satellite data. It was found that the impact of SST analysis on the atmospheric analysis was significant in the tropics. The difference in the SST produced difference in the precipitation in the forecast. The change in the initial guess divergent circulation associated with the changes in precipitation was large enough to impact the resulting analysis of winds as well as temperature. Finally, the use of radiance in the analysis has a very large impact on the analysis. The radiance analysis tends to enhance horizontal temperature gradients and disturbance intensity where other observations are not available.