Statistical Specification of the 500-mb Height Fields Using Smoothed Medium-Resolution Radiometric Fields of Nimbus II

Abstract

Over an area spanning the North American Continent from tropical to polar latitudes, and between 40W and 135W, four consecutive days of the NIMBUS II Medium Resolution Infrared (MRIR) five-channel equivalent blackbody temperatures and of 1000-mb geopotential fields were used to specify the 500-mb field of geopotential. Three of the four days were reserved for dependent data, the fourth day being reserved for independent test-case data. The data samples were stratified into ?extratropical? and subtropical-tropical areas, and then pooled three-day stepwise, with screening regression equations being developed by areas. In the lower latitude stratifications, the 500-mb regression equations were only of marginal significance, but in the extratropical zone (latitudes 32?64N), the regressions have 500-mb height specifications with multiple correlation coefficients of 0.95. Moreover, in the independent-data test case, no shrinkage of explained variances occurred in these extratropical latitudes. Here the most important predictors for Z5(I, J) were the equivalent blackbody temperatures (TBB) in the 14?16 ? and 10?11 ? channels, the 1000-mb geopotential, and finally an effective TBB associated with the solar-reflectance channel.