The Improvement of Clear Column Radiance Determination with a Supplementary 3.8 Micrometer Window Channel

摘要

Uner cloudy conditions relatively large errors in calculated clear column radiances for Infrared Temperature Profile Radiometer (ITPR) scan elements can arise where the cloud height is highly variable and where the cloud emissivity varies with wavelength. A method for detecting such cloud conditions using supplementary 3.8 microns window observations was developed and tested using simulated ITPR observations deduced from Nimbus II High Resolution Infrared Radiometer (HRIR) data. The clear column radiances derived with the aid of the 3.8 microns observations are much more precise than those calculated without this supplementary data. With 3.8 microns observations it appears possible to obtain more accurate clear column radiances for smaller areas and in regions of extremely high (but less than 100%) cloud cover. This knowledge should enable more accurate temperature soundings, down to the earth's surface, to be derived close to the centers of weather activity. (Author)