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The accuracy of SST retrievals from AATSR: Synthesis and Integration of comparisons to buoys and radiometers

Gary Corlett(1)

(1) University of Leicester, Space Research Centre, LE1 7RH Leicester, United Kingdom

Abstract

The Advanced Along-Track Scanning Radiometer (AATSR) was launched on Envisat in March 2002. The AATSR instrument is designed to retrieve precise and accurate global Sea Surface Temperature (SST). The formal specifications require that retrieved AATSR dual view SST values achieve an absolute accuracy of better than ± 0.5 K, with ± 0.3 K (one sigma) adopted by the project as the target accuracy. The accuracy of retrieved SST products from AATSR is assessed using two methods. First, the true accuracy of the AATSR SST products is determined through comparisons to in situ SST data from accurate infrared radiometers, mounted on ocean going ships of opportunity; these comparisons are performed against the 1 km high resolution AATSR NR product. Owing to the limited number of radiometers available, these comparisons are limited to certain regions of the globe. Secondly, global validation of the AATSR AR product has been performed through comparison with global in situ buoy data. This presentation summarises all AATSR SST validation activities that have occurred during the period from launch up to the ENVISAT Symposium 2007.

The AATSR SST validation activities to date indicate that the AATSR 1 km and 10' spatially averaged D3 SSTs are generally in specification, in that AATSR 1 km D3 SSTs have a warm bias of +0.10 K (σ = 0.28 K) in the Caribbean with a smaller bias +0.04 K (σ = 0.21 K) observed in the Bay of Biscay. Corresponding AATSR 10' D3 SSTs have a warm bias of +0.22 K (σ = 0.24 K) in the Caribbean with a smaller bias +0.05 K (σ = 0.33 K) observed in the Bay of Biscay. Detailed analysis of both D2-N2 and D3-N3 radiometer match-ups indicates a bio-modal distribution between cases of standard and non-standard atmospheric conditions. The difference between the dual and nadir retrieval can be used to provide improved confidence in the AATSR data by removing aerosol and cloud contaminated data. The requirement of having multiple long term validation data sets is emphasised to avoid incorrect conclusions on product accuracy.

 

Workshop presentation

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry