SOME IMPROVEMENTS ON THE PROCESSES TO OBTAIN ACCURATE MAPS OF SEA-SURFACE TEMPERATURE FROM AVHRR RAW DATA TRANSMITTED IN REAL-TIME .1. HRPTIMAGES

In this paper we have developed some improvements on the commonly used methodologies in order to obtain accurate maps of sea surface tempera ture (SST). These improvements permit us: (1) to calibrate without bia s AVHRR channels including non-linear corrections; (2) to get geometri cally corrected maps for the complete scan width of AVHRR (3000 km) wi th a subpixel accuracy; (3) to detect clouds over the sea; and (4) to make atmospheric and emissivity correction for all zenith angles from nadir to the outermost off-nadir view of AVHRR images (68.9 degrees) a nd for different types of atmospheres. The theoretical base of the imp rovements used is detailed in each section, and an example is also inc luded in each section in order to better explain how they are applied in a practical situation. The methodologies developed here can be prof itable for any user interested in accurate retrievals of SST such as m eteorologists, climatologists and oceanographers.