Effects of Atmospheric Water Vapor and Clouds on NOAA (National Oceanic and Atmospheric Administration) AVHRR (Advanced Very High Resolution Radiometer) Satellite Data

摘要

The last ten years have seen a revolution in large area surveys of the earth's biomass. Satellite spectral data have made a significant contribution to these surveys by virtue of the fact that various combinations of the data have been found to be sensitive indicators of the presence of green vegetation. Data from two solar reflective channels of the NOAA-7 meteorlogical weather satellite satellite's instantaneous field of view. In numerous instances the information content of this data cen be limited by the varying amounts of atmospheric constituents, by clouds, by view angle and by solar angle. This paper reports on a study which was undertaken to describe the effect of varying amounts of water vapor on the infrared portions of the solar reflected radiances and on the earth emitted, far infrared radiances. By virtue of several data screening processes, it was possible to determine that the change in atmospheric water content over a several day period was responsible for variations in the satellite-derived infrared radiance values. Similar variations were found in the far infrared radiance data. The variation in the near infrared channel was and is a factor in the variability of the vegetative index. A separate but related conclusion of this study is that view angle effects on the solar reflected near infrared channel introduces a larger variability into the data than was previously thought. This effect needs more study.