Climate parameters from satellite spectral measurements. Part I: Collocated AVHRR and HIRS/2 observations of spectral greenhouse parameter

Abstract An automated method of monitoring various climate parameters using collocated Advanced Very High Resolution Radiometer (AVHRR) and High-Resolution Infrared Sounder-2 (HIRS/2) observations has been developed. The method, referred to as CHAPS (collocated HIRS/2 and AVHRR products) was implemented during the months of July 1993 and January and July 1994. This paper presents the oceanic cloud screening method and analysis of the spectral greenhouse parameter (gλ) for July 1993 and January 1994. In addition, the CHAPS derived clear-sky parameters are compared to the NESDIS historical dataset. There is agreement between NESDIS and CHAPS for the g6.7 and g7.3. The NESDIS 8.2-µm data appears to be cloud contaminated. Through comparison with CHAPS, it is suggested that the mode, rather than the mean, provides the better estimate of the central tendency of the NESDIS clear-sky 8.2-µm radiance distribution, particularly for regions with extensive low-level cloud cover. It is shown that the spectral greenhou...