The CLAVR-1 cloudmask (Stowe, 1999) is used to cloudmask AVHRR high resolution sea surface temperature products. The cloudmask runs a series of tests on each surface temperature pixel to determine whether the pixel is contaminated by cloud cover. Users may evaluate which specific tests in the cloudmask returned positive cloud presence results by examining the value of the cloudmask. This value corresponds to an 8 bit binary number which details which tests flagged the pixel as a cloudy pixel. See http://coastwatch.pfel.noaa.gov/info/CLAVR.html for more information regarding the specific tests used in the cloudmask.