Analysis and interpretation of TIROS-N AVHRR infrared imagery, western Gulf of Mexico

Abstract

The early morning (0300 local time) 5 December 1978 TIROS-N overpass across the Gulf of Mexico coincided with the mild cold-air outbreak of 4–6 December. In the dry cloud-free region behind the cold front, the channel 4 data (thermal infrared 10.5–11.5 μm) of the TIROS-N Advanced Very High Resolution Radiometer (AVHRR) provided excellent radiometric data on the sea-surface temperature patterns. An AVHRR data calibration program has been developed to convert the thermal data to temperature in degrees Celsius and data from visible radiation channels into percent albedo. Digital interactive analysis of the calibrated channel 4 data in the cloud-free region behind the front revealed a series of oceanographic features in the sea-surface temperature patterns. Temperature differences of 6–8°C occurred between the inner shelf and deep Gulf waters. Estuarine discharge plumes 2°C cooler than shelf waters and a large cyclonic eddy with isothermal core are discernible in the enhanced 0.25°C thermal resolution, 1.1-km spatial resolution imagery. The radiometric sea-surface temperatures are 2°C below surface measurements made by two NOAA data buoys anchored along the 26°N parallel in the deep Gulf. Under these atmospheric and oceanic conditions, the satellite data available from the digital archives of the National Climatic Center are a valuable record of continental shelf and near-surface deep-ocean processes.