Note on the quality of the (A)ATSR land surface temperature record from 1991 to 2009

Land-surface temperature (LST) is a key parameter in the physical study of atmosphere-land interactions as well as for global warming and climate change monitoring on a longer timescale. Remote sensing provides an excellent way to measure LST at a global scale with appropriate spatial and temporal resolution. To retrieve LSTs, measured radiances at the sensor have to be corrected for surface emissivity, atmospheric effects and contaminating clouds. This study is based on the LST data provided by the Along-Track Scanning Radiometers (ATSR-1 and ATSR-2) and the Advanced ATSR (AATSR) on board the three European Space Agency (ESA) satellites, European Remote-Sensing Satellite 1 (ERS-1), ERS-2 and Enviromental Satellite (ENVISAT). The analysis covers data from August 1991 up to December 2009 and contains detailed investigations on global as well as on regional scales with a temporal resolution of 1 month, outlining problems and restrictions within the time series mainly due to cloud contamination and effects of calibration drifts on the cloud detection tests. It is demonstrated that the trends observed, for cooling as well as for warming, are likely to be related to the trends in cloud contamination rather than the trends in the actual LST.