Inter-comparison of AVHRR and MODIS sea surface temperature

Since 1997, the INTA (National Institute for Aerospace Technology)-CREPAD (Centre for REception, Processing, Archiving and Dissemination of Earth Observation Data) program distributes freely some of the most demanded low-resolution remote sensing products. In the frame of the CREPAD program a comparison between the SST (Sea Surface Temperature) computed with the MATIAS software from AVHRR data and the SST computed with SeaDAS from MODIS data has been done and is presented in this paper. Images over the finger print of the Canary Space Centre (Centro Espacial de Canarias, CEC) acquired in 2008 have been used in this study. Time acquisition difference between the images to be compared should be lower that 4 hours and the temperature range should be in between 10 degrees C and 30 degrees C. In this study less favourable results are observed in images with few pixels compared. These images are usually cloudy images or images with the compared area falling in the edge of the image with high satellite zenith angle values. Therefore results have been studied related to the percentage of compared pixels in each image. Images with more than 30% pixels compared showed a mean SST difference of about 0.1 degrees C, the standard deviation was 0.5 and the correlation between AVHRR and MODIS SST images was 0.90. The mean SST difference is lower than 0.5 degrees C in 61% of the pixels and lower than 0.8% in 82% of the pixels. The finger print of the CEC covers areas with different behaviour therefore results are shown over preselected CREPAD areas. Those areas are: Africa, Albor-n Sea, Atlantic Ocean, Azores, Canaries, Cant-brico and Mediterranean Sea.