Land and Sea Surface Temperature Time Series from AVHRR Data over Europe: Generation, Validation and Analyses of a long-term Archive

Kurzfassung

Europe has emerged as a global climate change hotspot, warming at about 0.5 K per decade since the 1980s and exceeding the global mean temperature increase. Robust assessment of these changes requires long-term, climate-quality datasets of Essential Climate Variables, particularly Land Surface Temperature (LST) and Sea Surface Temperature (SST). While MODIS provides high-quality LST observations since 2000, its record is too short for multi-decadal trend analysis. The Advanced Very High Resolution Radiometer (AVHRR) archive, extending back to the early 1980s, offers unique potential, but its use for LST has been limited by sensor inconsistencies and orbital drift. SST records from AVHRR are well established, though typically available at coarse spatial resolution. This thesis generates and analyzes long-term, climate-quality LST and SST datasets over Europe at 1 km spatial resolution based on AVHRR. A systematic review of 164 peer-reviewed studies highlighted the dominance of short and regionally biased LST records and a lack of climate-relevant time series exceeding 30 years. For LST, instantaneous retrievals were harmonized across 13 NOAA satellites using mono- and split-window algorithms, radiometric inter-calibration, and corrections for emissivity, atmosphere, and view angle. A novel orbit drift correction based on SEVIRI annual cycle parameters normalized observations to a fixed local solar time. Validation against in situ measurements and MODIS yielded RMSEs below 2.7 K. Using the resulting dataset, monthly maximum LST anomalies from 1986 to 2018 revealed significant warming of about +0.8 K per decade over Central and Southern Europe, with pronounced spatial variability linked to land cover and elevation. The framework was extended to SST, producing a 1 km dataset validated against buoy observations and ESA CCI SST. Trend analyses from 1990 to 2022 identified strong warming in European marginal seas, particularly in coastal regions. Overall, the results demonstrate the potential of harmonized AVHRR archives for long-term, high-resolution climate monitoring of Europe’s land and coastal surfaces.