An assessment of NIMBUS 7 ERB Shortwave Scanner data by correlative analysis with narrowband CZCS data

Abstract

As a check on calibration adjustment factors, the broadband ERB shortwave scanning channel data from NIMBUS 7 were compared with independent narrowband satellite measurements. This check required the establishment of appropriate broadband‐narrowband radiance relationships, which also become the basis for generating or evaluating radiation budget parameters in either spectral range from data in the other. As a theoretical basis for comparison both broadband and narrowband radiances were simulated from the DAVE dataset of radiative transfer model computations for a variety of angles through several model atmospheres. Spectrally varying reflectances for five basic surface types (vegetations, desert, cloud, water, snow) were introduced along with spectral response functions for narrowband intervals. Linear regression relationships were developed for individual surface types and for the combination of all surface types under identical illumination‐viewing conditions. Empirical relationships were generated from actual matchups of earth radiation budget (ERB) scanner data with coincident data from CZCS channel 5 (0.7–0.8 μm) over a variety of scenes. Since each of the four scanning channels of ERB was compared separately with narrowband data from the same sensor, relative differences were accurately determined from the empirical data. Previously established calibration adjustment factors for the ERB shortwave scanning channels verified, in a relative sense, regardless of surface type, to within 2%.