Future Development of the Operational Aatsr Lst Product

Since March 2004, an operational land surface temperature (LST) product has been derived from data recorded by ESA’s Advanced Along-Track Scanning Radiometer (AATSR onboard Envisat). The algorithm, which utilises a nadir-only split window retrieval, will also be applied operationally to data recorded by the AATSR’s predecessors, ATSR-1 (ERS-1) and ATSR-2 (ERS-2), leading to a > 15-year record of global LST data. The target accuracy of the product is 1.0 K at night, and 2.5 K during the day. Extensive comparisons between the operational AATSR LST product and other in situ and satellite LST data sets have been performed at a number of sites around the globe. The results of these studies, whilst generally very encouraging, have highlighted the need for a number of algorithm improvements. We present a summary of the key results where these issues in the current operational algorithm are apparent and describe potential improvements. In particular, we address the issues relating to the resolution of the auxiliary land classification and fractional vegetation data that are used to tune the operational retrieval algorithm to the expected surface and atmospheric conditions at a given location. Presently, these data are tabulated at 0.5 degree resolution and we demonstrate that the product would benefit greatly from increasing the resolution of these data sets. Problems with the sensitivity of the current algorithm to atmospheric and surface conditions are also discussed.