Inversion of AMSR‐E observations for land surface temperature estimation: 1. Methodology and evaluation with station temperature

• Published in: Journal of geophysical research. Atmospheres Vol. 122; no. 6; pp. 3330 - 3347
• Main Authors: Jiménez, C., Prigent, C., Ermida, S. L., Moncet, J.‐L.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 27-03-2017; American Geophysical Union
• Subjects: Approximation; Astrophysics; Atmospheric conditions; Brightness; Brightness temperature; Climatology; Earth; Emissivity; Estimates; Evaluation; Flags; Geophysics; Ground stations; Imaging techniques; Inversions; Land surface temperature; Meteorological satellites; Methods; Microwaves; MODIS; Neural networks; Physics; Radiometers; Retrieval; Satellite observation; Satellites; Scanning; Sciences of the Universe; Sky; Stations; Surface temperature; Temperature; Temperature effects; Temperature inversion; Temperature inversions; Training; Uncertainty; Vegetation
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2016JD026144

Inversions of the Earth Observation Satellite (EOS) Advanced Microwave Scanning Radiometer (AMSR‐E) brightness temperatures (Tbs) to derive the land surface temperature (Ts) are presented based on building a global transfer function by neural networks trained with AMSR‐E Tbs and retrieved microwave Ts*. The only required inputs are the Tbs and monthly climatological emissivities, minimizing the dependence on ancillary data. The inversions are accompanied by a coarse estimation of retrieval uncertainty, an estimate of the quality of the retrieval, and a series of flags to signal difficult inversion situations. For ∼75% of the land surface the root‐mean‐square difference (RMSD) between the training target Ts* and the neural network retrieved Ts is below 2.8 K. The RMSD when comparing with the Moderate Resolution Imaging Spectroradiometer (MODIS) clear‐sky Ts is below 3.9 K for the same conditions. Over 10 ground stations, AMSR‐E and MODIS Ts were compared with the in situ data. Overall, MODIS agrees better with the station Ts than AMSR‐E (all‐station mean RMSD of 2.4 K for MODIS and 4.0 for AMSR‐E), but AMSR‐E provides a larger number of Ts estimates by being able to measure under cloudy conditions, with an approximated ratio of 3 to 1 over the analyzed stations. At many stations the RMSD of the AMSR‐E clear and cloudy sky are comparable, highlighting the ability of the microwave inversions to provide Ts under most atmospheric conditions. Closest agreement with the in situ Ts happens for stations with dense vegetation, where AMSR‐E emissivity is less varying.
Key Points
Development of a land surface temperature (Ts) product from AMSR‐E observations
Evaluation at ground stations together with MODIS infrared Ts to highlight issues and difficulties of the inversions
Overall, MODIS agrees better with the station Ts, but AMSR‐E can provide 3 times more estimates