A Preliminary Study of the Applicability of Nimbus 6 ESMR to Sea-Surface Wind Speed Estimates.

Abstract : The utility of the Nimbus 6 ESMR for sea-surface wind determination is explored in this study by: (1) analysis of wind equations derived from theoretical calculations of brightness temperatures above model atmospheres and assumptions of linear increases in sea-surface emissivities with wind, and (2) actual analysis of Nimbus 6 ESMR brightness temperatures in areas of known wind. Unfortunately a calibration problem in the Nimbus 6 ESMR prevented quantitative comparisons of brightness temperatures and wind, and the derivation of a sound empirical relationship between wind and sea-surface emissivities needed to estimate winds from satellite-measured brightness temperatures. Notwithstanding the erroneous calibration, analyses of ESMR brightness temperatures maps do show definite increases in horizontally and vertically polarized brightness temperatures with wind. Such increases are dramatically brought out in a Mistral occurrence over the Mediterranean Sea. An error analysis on derived wind equations establishes the accuracy of wind speed determination from Nimbus 6 ESMR under various conditions.