Use of meteosat data for validation of the diurnal variation of the outgoing longwave radiation produced by ERBE

Radiative transfer calculations have been performed to demonstrate the usefulness of the Meteosat observations in the relative narrow-band of the water vapour absorption (WV, 5.7-7.1 μm) in addition to the observations in the atmospheric infrared window (IR, 10.5-12.5 μm) to deduce the integrated thermal outgoing longwave radiation (OLR). A statistical analysis of colocated and nearly simultaneous Meteosat and the Earth Radiation Budget Experiment (ERBE) data has yielded regression coefficients for estimating the OLR with Meteosat data during the months of April and July 1985. These results have been used to study the mean diurnal variation of the outgoing longwave radiation. The results show that in some cases, because of inadequate time sampling, the form (and especially the phase) of the longwave (LW) diurnal cycle is incorrectly determined by ERBE, but that Meteosat data can improve the determination. In nearly all cases, such errors have little or no influence on the determination of monthly mean LW flux fields.