Evaluation of the AVHRR surface reflectance long term data record between 1984 and 2011

The long-term data record (LTDR) from the Advanced Very High-Resolution Radiometer (AVHRR) provides daily surface reflectance with global coverage from the 1980s to present day, making it a unique source of information for the study of land surface properties and their long-term dynamics. Surface reflectance is a critical input for the generation of products such as vegetation indices, albedo, and land cover. Therefore, it is of utmost importance to quantify its uncertainties to better understand how they might propagate into downstream products. Due to the prolonged length of the surface reflectance LTDR and previous unavailability of a well calibrated reference, no comprehensive evaluation of the complete record has been reported so far. Recently, the United States Geological Survey (USGS) began production of surface reflectance datasets from the Landsat 4–8 satellites, which provide a suitable reference against which the LTDR can be compared to. In this study, we evaluate the LTDRV5 between 1984 and 2011 using surface reflectance data from the Landsat-5 Thematic Mapper (TM5) Collection-1 as a reference. Data from TM5 was obtained from over 740,000 globally distributed scenes which gave a representative set of land surface types and atmospheric conditions. Differences due to observation geometry were accounted for using the Vermote-Justice-Breon (VJB) Bidirectional Reflectance Distribution Function (BRDF) normalization method to adjust the AVHRR surface reflectance to TM5 observation conditions; the spectral response differences were minimized using spectral band adjustment factors (SBAFs) derived from the Earth Observing One (EO-1) Hyperion atmospherically corrected hyperspectral spectra. The performance of the AVHRR record is reported in terms of the accuracy, precision, and uncertainty (APU). Results show that the LTDR performance is close or within the combined uncertainty specification of 0.071ρ + 0.0071, where ρ is the estimated reflectance.