THE DETERMINATION OF SEA-SURFACE TEMPERATURE FROM SATELLITE HIGH RESOLUTION INFRARED WINDOW RADIATION MEASUREMENTS

Abstract

A statistical histogram method is developed to objectively determine sea-surface temperature from satellite high resolution window radiation measurements. The method involves inferring the distribution of surface radiances for the clear atmospheric case from observed histograms of generally cloud-contaminated radiances. The brightness temperature associated with the clear atmosphere modal peak radiance is the statistically most probable surface temperature. The reliability of the inferred surface temperature depends upon the number of cloud-free measurements available to define the clear mode. The method accounts for atmospheric attenuation and instrumental noise and also objectively discriminates cloud-free from cloud-contaminated observations. The statistical histogram method is applied to 3.8 micrometer window radiation data obtained by the High Resolution Infrared Radiometer flown on the Nimbus 2 and Nimbus 3 satellites. Examples of sea temperatures inferred over both small and large areas are presented. Comparisons with conventional ship observations indicate that both bias and random errors of the inferred sea temperatures are less than 1°C. Due to the apparent success of this statistical histogram technique, plans have been made to use it to obtain sea-surface temperatures on a global basis daily from operational high resolution infrared radiation measurements.