A SEARCH FOR CORRELATIONS BETWEEN SEA SURFACE TEMPERATURES AND OPTICAL REFLECTANCES IN CHILE AND BRAZIL DERIVED FROM AVHRR/NOAA IMAGES

Abstract

A search is made for indicators of the presence of phytoplankton, using satellite images of the Pacific (Central Chile) and Atlantic (South Brazil). AVHRR/NOAA-16 and -17 visible (1 and 2) and thermal (4 and 5) channels were used to perform a detection test, respectively, the Suspended Particulate Matter (SPM) and the Sea Surface Temperature (SST). In Brazilian waters, a positive correlation is found between SST and SPM's reflectance. This is interpreted as due to phytoplankton being more abundant in colder waters, where nutrients availability are higher because CO2 dissolution rates, thus being a favorable environment for phytoplankton contents, which when mixed with SPM, tends to reduce the total water reflectance, since organic matter causes absorption at red wavelengths. A comparison is made with results for colder Pacific, where an opposite trend is found. It is noted that the Pacific shelf, off Chile, is narrower than the Atlantic's off Brazil, leading to circulation processes, which have a different influence on particulate matter contents. It's also concluded that NOAA data is suitable for these studies, despite the fact its spectral resolution is poorer comparing to specialized ocean studies satellites, a disadvantage compensed by its wider spectral and radiometric range and higher imaging frequency