Methodology to obtain accurate sea surface temperature from locally received NOAA-14 data in the Canary-Azores-Gibraltar area

Abstract

A methodology to obtain the sea surface temperature (SST) in the Canary-Azores-Gibraltar area has beendeveloped. The final accuracy of the AVHRR-based SST retrievals depends both on the accuracy of the measured radianceand the accuracy of the SST retrieval algorithm that converts the measured radiance into sea surface temperature. The pro-cedure made in this framework consists of: (i) a radiance-based non-linearity correction method; (ii) an automatic procedurefor the geometric correction, achieving accuracy to the order of the pixel; (iii) an improved algorithm for cloud detection,based on the method of the multiband thresholds; (iv) a new split-window function (SWF) to perform atmospheric correc-tion in CANIGO area. This task has been accomplished by using the matchup data set of AVHRR brightness temperature(channel 4 and 5) and in situ SST data. The matchups were carefully screened from the HRPT scenes of all seasons in 1996-1998. The temporal and spatial coincidences are within 30 minutes and one pixel resolution, respectively. Coefficients ofthat algorithm are estimated from regression analysis using 60 co-located in situ and satellite measurements (matchups).Error analysis has shown that SST can theoretically be retrieved to within 0.38ºC RMS.