Intercomparison of AVHRR PAL and LTDR Version 2 Long-Term Data Sets for Africa From 1982 to 2000 and Its Impact on Mapping Burned Area

The long-term data record (LTDR) project funded by the National Aeronautics and Space Administration has created a global daily data set at 0.05deg spatial resolution, approximately 5 km, for environmental science applications. The LTDR uses observations from the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer and is intercalibrated with the Moderate Resolution Imaging Spectroradiometer instruments. This letter compares the latest LTDR version 2 with the Daily Tile Pathfinder 8-km land data set (PAL) for a relatively stable radiometric region over the Libyan desert from 1982 to 2000. In channel 1 (0.63 mum, rho 1 ), LTDR was 3.3% larger with respect to PAL, and, in channel 2 (0.83 mum, rho 2 ), it was 18.8% larger. An offset appeared between NOAA 11 and 14 satellites of 0.04 and 0.06 in rho 1 and rho 2 , respectively, for LTDR but not for PAL; that offset needs to be accounted for when developing new LTDR algorithms. On the other hand, a 3-K offset between NOAA 11 and 14 was found for the PAL brightness-temperature channel ( ~ 3.75 mum, T 3 ), but not for LTDR. These results were consistent with those obtained over seven other contrasted sites in Africa. As a result of these differences, burned area for Africa, calculated with both data sets for the same algorithm, shows 4.60 times lower values for the LTDR data set with respect to PAL across the entire time series, particularly for NOAA 14. Therefore, algorithms used for PAL need to be tested and redefined when applied to LTDR.