An experimental 2D-Var retrieval using AMSR2
<p>A two-dimensional variational retrieval (2D-Var) is presented for a passive microwave imager. The overlapping antenna patterns of all frequencies from the Advanced Microwave Scanning Radiometer 2 (AMSR2) are explicitly simulated to attempt retrieval of near-surface wind speed and surface sk...
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2019-12-01
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doaj-a763e4e1e7554fc19434728be95b78eb2020-11-25T02:20:16ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482019-12-01126341635910.5194/amt-12-6341-2019An experimental 2D-Var retrieval using AMSR2D. I. Duncan0D. I. Duncan1P. Eriksson2S. Pfreundschuh3Department of Space, Earth, and Environment, Chalmers University of Technology, Gothenburg, Swedennow at: ECMWF, Reading, UKDepartment of Space, Earth, and Environment, Chalmers University of Technology, Gothenburg, SwedenDepartment of Space, Earth, and Environment, Chalmers University of Technology, Gothenburg, Sweden<p>A two-dimensional variational retrieval (2D-Var) is presented for a passive microwave imager. The overlapping antenna patterns of all frequencies from the Advanced Microwave Scanning Radiometer 2 (AMSR2) are explicitly simulated to attempt retrieval of near-surface wind speed and surface skin temperature at finer spatial scales than individual antenna beams. This is achieved, with the effective spatial resolution of retrieved parameters judged by analysis of 2D-Var averaging kernels. Sea surface temperature retrievals achieve about 30 km resolution, with wind speed retrievals at about 10 km resolution. It is argued that multi-dimensional optimal estimation permits greater use of total information content from microwave sensors than other methods, with no compromises on target resolution needed; instead, various targets are retrieved at the highest possible spatial resolution, driven by the channels' sensitivities. All AMSR2 channels can be simulated within near their published noise characteristics for observed clear-sky scenes, though calibration and emissivity model errors are key challenges. This experimental retrieval shows the feasibility of 2D-Var for cloud-free retrievals and opens the possibility of stand-alone 3D-Var retrievals of water vapour and hydrometeor fields from microwave imagers in the future. The results have implications for future satellite missions and sensor design, as spatial oversampling can somewhat mitigate the need for larger antennas in the push for higher spatial resolution.</p>https://www.atmos-meas-tech.net/12/6341/2019/amt-12-6341-2019.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
D. I. Duncan D. I. Duncan P. Eriksson S. Pfreundschuh |
spellingShingle |
D. I. Duncan D. I. Duncan P. Eriksson S. Pfreundschuh An experimental 2D-Var retrieval using AMSR2 Atmospheric Measurement Techniques |
author_facet |
D. I. Duncan D. I. Duncan P. Eriksson S. Pfreundschuh |
author_sort |
D. I. Duncan |
title |
An experimental 2D-Var retrieval using AMSR2 |
title_short |
An experimental 2D-Var retrieval using AMSR2 |
title_full |
An experimental 2D-Var retrieval using AMSR2 |
title_fullStr |
An experimental 2D-Var retrieval using AMSR2 |
title_full_unstemmed |
An experimental 2D-Var retrieval using AMSR2 |
title_sort |
experimental 2d-var retrieval using amsr2 |
publisher |
Copernicus Publications |
series |
Atmospheric Measurement Techniques |
issn |
1867-1381 1867-8548 |
publishDate |
2019-12-01 |
description |
<p>A two-dimensional variational retrieval (2D-Var) is presented for a passive microwave imager. The overlapping antenna patterns of all frequencies from the Advanced Microwave Scanning Radiometer 2 (AMSR2) are explicitly simulated to attempt retrieval of near-surface wind speed and surface skin temperature at finer spatial scales than individual antenna beams. This is achieved, with the effective spatial resolution of retrieved parameters judged by analysis of 2D-Var averaging kernels. Sea surface temperature retrievals achieve about 30 km resolution, with wind speed retrievals at about 10 km resolution. It is argued that multi-dimensional optimal estimation permits greater use of total information content from microwave sensors than other methods, with no compromises on target resolution needed; instead, various targets are retrieved at the highest possible spatial resolution, driven by the channels' sensitivities. All AMSR2 channels can be simulated within near their published noise characteristics for observed clear-sky scenes, though calibration and emissivity model errors are key challenges. This experimental retrieval shows the feasibility of 2D-Var for cloud-free retrievals and opens the possibility of stand-alone 3D-Var retrievals of water vapour and hydrometeor fields from microwave imagers in the future. The results have implications for future satellite missions and sensor design, as spatial oversampling can somewhat mitigate the need for larger antennas in the push for higher spatial resolution.</p> |
url |
https://www.atmos-meas-tech.net/12/6341/2019/amt-12-6341-2019.pdf |
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