VALIDATION OF A TECHNIQUE FOR ESTIMATING OUTGOING LONGWAVE RADIATION FROM HIRS RADIANCE OBSERVATIONS

Simultaneous observations by the Earth Radiation Budget Experiment (ER BE) scanning radiometer and the High-Resolution Infrared Sounder (HIRS ) on board the NOAA-9 spacecraft have been used to validate a multispe ctral technique for estimating the outgoing longwave radiation (OLR) f rom the earth-atmosphere system. Results from approximately 100 000 co llocated observations show that the HIRS technique provides instanteou s OLR estimates that agree with the ERBE observations just as well as different ERBE scanners agree with each other-about 5 W m-2 rms. Altho ugh there are differences between the HIRS and ERBE estimates that dep end upon the scene type and time of day, the HIRS technique explained more than 99% of the variance of the ERBE observations for both day an d night observations. The results suggest that the HIRS OLR technique is a suitable replacement for the Advanced Very High Resolution Radiom eter technique now used by the National Oceanic and Atmospheric Admini stration for operational estimates of the OLR.