Comparison of Scanner and Wide-field-of-view Emitted Radiation Measurements from ERBE NOAA 9 Satellite

Abstract

The Earth Radiation Budget Experiment (ERBE) uses narrow-field-of-view (NFOV) scanning radiometer instruments and wide-field-of-view (WFOV) instruments to measure reflected shortwave and emitted longwave radiation (OLR) of the earth. On a regional basis, the measurements are displayed in 2.5, 5, and 10 degree regions. The scanner has the highest resolution. The WFOV measurements, enhanced with a numerical filter technique, has the next best resolution, and the WFOV measurements from the shape factor technique has the lowest resolution with no enhancing or smoothing. To see how well the scanner gridded measurements of OLR agrees with numerical-filter and shape-factor measurements of OLR, difference maps were made using measurements from the instruments aboard the NOAA 9 ERBE satellite. The scanner measurements were combined from 2.5 degree to 5 degree regions to be compatable with the 5 degree numerical-filter results. Many regions had large differences, from –30 to +30 watts per square meter. These large differences at 5 degree grid regions are due in part to temporal sampling, and one way to get around the temporal sampling problem is to combine grids to lower resolution consistent with the WFOV instrument. Scanner measurements were combined to 10 degree resolution regions and compared with the shape-factor results (shape-factor is limited to 10 degree regions). These differences had less structure and variability and are an improvement over the numerical-filter 5 degree results. The third comparison gave the best results when looking at differences. In this comparison, the scanner minus numerical filtered measurements were combined to 10 degree regions. The differences were more uniform, with differences mostly in the range from –5 to +5 watts per square meter. Thus, for comparing scanner and nonscanner measurements, 10 degree grids and numerical-filter data from the WFOV instrument may give optimum results for comparing with scanner measurements.