Inter-comparison of Land Surface Temperature products from NPP/VIIRS and Aqua/MODIS – Protocol, Limitations and Validation Results

Land Surface Temperature (LST) products derived from the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument onboard the Suomi - National Polar-orbiting Partnership (Suomi-NPP) satellite provide key information for monitoring Earth surface energy and water fluxes. Because users of satellite products put a high priority on the provision of product accuracy, validation of LST products is of crucial importance for estimating the accuracy of the operational products and understanding the potential and limitations of satellite observations. VIIRS LST products must be carefully evaluated and cross-calibrated with the data products derived from predecessor instruments if we are to obtain continuous scientific data sets that cover the largest possible portions of the entire period of record. To this end, we compare the LST products derived from VIIRS and from the MODerate resolution Imaging Spectrometer (MODIS) instrument onboard the Aqua satellite. This comparison provides important quality information regarding the overall consistency between the two products, as well as characterization of spatio-temporal patterns in the LST differences. In this study, we provide details of our process for matching the two datasets, present the complexity involved, and outline a validation protocol and its limitations. We identify a large number of near-simultaneous overpass events over the contiguous United States where swaths from each instrument were acquired within 10 minutes of each other from orbital planes separated by 2° of arc or less. These constraints are chosen to reduce directional effects. The VIIRS data are resampled to the MODIS swath pixel locations, and the data from both instruments are filtered so that only high quality values are retained. We compare day and night LST and radiance values by land surface type. Overall, the VIIRS and MODIS LST products are found to be in good agreement with one another.