Evaluation of the Daytime corrected AVHRR Land Surface Temperature Time Series

Abstract

For monitoring conditions repeatedly over large areas, satellite derived LST has become an indispensable tool. However, to make climate relevant statements and quantify the impact of land surface variables over long time, we need sensors that are available for more than 30 years. The AVHRR is the only sensor providing spatially and temporally continuous, daily measurements for 40 years. The TIMELINE project of the German Aerospace Center (DLR) aims at the generation of a homogeneous multi-decadal time series from AVHRR data (3 different AVHRR sensors on 16 platforms) over Europe and North Africa. However, different observation times of the AVHRR sensors affect the observed temperature and therefore the AVHRR LST time series. In addition, the orbital drift effect, resulting in a slowly changing observation time during the lifetime of one sensor is influencing the time series. In this study, a new approach for correcting daytime effects in the AVHRR LST time series is presented. This approach is then validated by comparing observations from different AVHRR platforms of the same day and checking the corrected AVHRR LST time series against the CCI LST time series as well as against in situ air temperature observations.