Cloud Clearing over the Ocean in the Processing of Data from the Along-Track Scanning Radiometer (ATSR)

Infrared radiometric measurements of surface parameters are prone to error if clouds are present in the observation path. The along-track scanning radiometer (ATSR) with its novel dual-view feature is able to correct for absorption effects in the clear atmosphere more precisely than previous instruments; hence, it is especially important in this case for the retrieved surface temperatures not to be cloud contaminated. The algorithms used for identifying cloud in the routine processing of the ATSR data are described. These tests rely heavily on the previous experience gained by using data from the Advanced Very High Resolution Radiometer (AVHRR). Modifications to the original AVHRR tests, and the new tests developed, are given in detail.