Correction for aerosols effects on satellite sea surface temperature measurements

Estimation of Sea Surface Temperature (SST) from split-window algorithms for NOAA-AVHRR data can be determined with rms values of 0.7 K on a global basis. However, this figure is not compatible with the stringent accuracy of 0.3 K required by climate studies. Among the different sources of errors, the presence of tropospheric aerosols in the satellite field of view prevents the retrieval of accurate satellite SSTs. Still, the effect of aerosols on temperature measurements derived from remote sensing techniques has been traditionally overlooked. Very few studies have addressed the problem of giving split-window algorithms which incorporate aerosol correction, although retrieving algorithms of the aerosol loading from the images do exist. The aim of this study is the evaluation of the effect of the aerosols on the SST measurements obtained from the AVHRR sensor. With this objective we accomplish a simulation study by using MODTRAN code. Such code was used to compute the upwelling radiances and, subsequently, the brightness temperatures under cloud-free conditions. The filter response functions for the NOAA14 instrument are used to produce theoretical brightness temperatures for the zenith angles : 0 degrees, 30 degrees and 55 degrees. The results show that for most of all the atmospheres that we have considered, deviations as far as 0.8 K are reached compared with the case in which the aerosols are not considered. It's important to point up that deviations higher than 0.4 K are able to mask the improvement introduced by a diminution of the Noise Equivalent Temperature (NE Delta T) in the new sensors as a consequence of error propagation.