Resolution of the Nimbus High Resolution Infrared Radiometer

Abstract

For the purpose of evaluating the resolution of the High Resolution Infrared Radiometer (HRIR) flown on board the Nimbus I meteorological satellite, three cloud-free regions in the western United States?the Grand Canyon, Death Valley, and Sierra Nevada?were selected. Enlarged HRIR pictures and the analog frequency traces of the scan lines in the pictures were examined in an attempt to investigate the types of noise superimposed on the signals. Two types of noise which appear in periodic and oscillatory fashions were found. The latter can be eliminated by taking running-mean values at one-degree scan angle intervals. The equivalent blackbody temperatures thus obtained were analysed over these three regions, leading to the determination of the apparent temperature lapse rate inside the Grand Canyon atmosphere and of the temperature of Lake Tahoe and other lakes in the Sierra Nevadas. Death Valley was found to be about 10C warmer than the surrounding desert area 5000 ft high. An attempt was also made to produce an HRIR picture with isoneph contours similar to the iso-echo presentation of radar pictures.