The HIRS outgoing longwave radiation product from hybrid polar and geosynchronous satellite observations

Abstract Traditionally, earth radiation budget studies use polar orbiting satellites to estimate the global distribution of outgoing longwave radiation (OLR). However, the two-pass per day per satellite orbit significantly limits the accuracy of the daily mean OLR due to diurnal variations. Geosynchronous satellites, on the other hand, have high temporal resolution but have less spatial coverage. To increase the accuracy of daily mean of the High Resolution Infrared Radiation Sounder (HIRS) OLR, one could blend the OLR from polar orbiters with the diurnal information provided by the geosynchronous satellite observations. We demonstrate a scheme to generate a hybrid OLR product by integrating the HIRS observations on board of the US National Oceanic and Atmospheric Administration polar satellites and the Geostationary Operational Environment Satellite Imager observations. This kind of product can be utilized to avoid the day/night bias that may appear when broadband longwave is derived from spectral subtraction of a SW signal from an unfiltered total channel with errors in calibration of the short wave part of the spectrum. The paper investigated the errors in the HIRS daily mean OLR at averaging domains of various temporal and spatial scales.