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Proceedings Paper

Improved wind-field retrieval for low and high wind speeds
Author(s): Paul Snoeij; P. A.E.M. Janssen; W. A. Oost; D. van Halsema; C. J. Calkoen
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Paper Abstract

Using scatterometer data from ERS-1 we have shown that realistic wind fields may be obtained with the VIERS scatterometer algorithm. The VIERS algorithm determines for given parameters such as wind speed and direction, sea state and radar incidence angle, the radar backscatter at the ocean surface. Thus, by inverting the algorithm the wind field over the ocean may be determined from the observed radar backscatter provided the sea state (given by the WAM model) is known. The inversion of the algorithm was achieved by means of minimization of a cost function that penalizes deviations between modeled and observed radar backscatter and deviations between retrieved and atmospheric model wind direction. The retrieved wind fields are in good agrement with analyzed ECMWF winds. Compared to the present operational CMOD4 algorithm we found that the VIERS algorithm performs better in extreme conditions; in the high wind speed regime wind waves are in a relatively early stage of development and are therefore so steep that the radar backscatter from the short waves is affected. From a synoptic study we have concluded that the VIERS winds are of high quality. The VIERS algorithm performs well in cases of frontal systems, for example, and only occasionally problems with the wind direction ('the ambiguity problem') occur. The end result is that we have developed a scatterometer algorithm based on our present knowledge of the physics of the relevant processes. From the observed radar backscatter this algorithm enables us to obtain reliable wind fields.

Paper Details

Date Published: 18 December 1995
PDF: 11 pages
Proc. SPIE 2586, Global Process Monitoring and Remote Sensing of the Ocean and Sea Ice, (18 December 1995); doi: 10.1117/12.228612
Show Author Affiliations
Paul Snoeij, Delft Univ. of Technology (Netherlands)
P. A.E.M. Janssen, Royal Netherlands Meteorological Institute (Netherlands)
W. A. Oost, Royal Netherlands Meteorological Institute (Netherlands)
D. van Halsema, TNO (Netherlands)
C. J. Calkoen, Delft Hydraulics (Netherlands)

Published in SPIE Proceedings Vol. 2586:
Global Process Monitoring and Remote Sensing of the Ocean and Sea Ice
Donald W. Deering; Preben Gudmandsen, Editor(s)

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