A Multispectral Technique to Determine Sea Surface Temperature Using Nimbus 2 Data

Abstract

Three channels of the Nimbus 2 five-channel Medium Resolution Infrared Radiometer (MRIR) have been employed in the development of a technique to determine sea surface temperature. Two of the channelsin the 0.2-4.0 and 6.4-6.9 μm spectral regions are used to indicate a cloud-free line of slight and the third, a high signal-to-noise window channel (10-11 μm), measures the equivalent blackbody temperature (TBB) which is a function of the thermal emission from the sea surface and the intervening atmosphere. Equivalent blackbody temperatures and normalized reflectance thresholds were established using frequency distributions from the 6.4-6.9 and 0.2-4.0 μm channels, respectively, to determine the existence of cloud-free conditions. The window TBB's were compared with ship ocean temperature measurements for a one-month period over the western North Atlantic. This comparison revealed a ±1.5K dispersion about the mean difference between the ship temperatures and window TBB's between 31-34N. An empirical method has been developed to correct for the atmospheric contribution to the observed window TBB's that considers the measurements from the other two channels and the viewing angle from the radiometer to the ocean surface.