Comparison between Nimbus-7 SMMR and ECMWF Model Analyses: The Problem of the Surface Latent Heat Flux

Abstract

Nimbus-7 SMMR data of sea surface temperature, surface wind and precipitable water are compared to the ECMWF model daily analyzes for the first Special Observing Period of the FGGE Period (January-February 1979). The comparison of these fields shows some SMMR instrumental problems that were not resolved in the available geophysical data (SST and surface wind fields), but are still in discussion. Problems with analyzed fields are also revealed, particularly concerning the humidity field. The conclusion is that SMMR could not have been directly used for model assimilation, but there is a need for wind and humidity data assimilation. Scatterometers will be necessary for obtaining surface wind, but water vapor from microwave radiometers could help in testing the model hydrological cycle. The surface latent heat flux computed at the first guess of the ECMWF model is also compared to the flux obtained by applying Liu's method from Nimbus-7 SMMR data. Important quantitative differences between the two flux estimates are observed. Liu's method is tested by applying it to the model mean fields. The importance of the humidity field is shown by computing the latent heat flux using the model surface fields and the SMMR precipitable water field.