Marine wind speed retrieval from RADARSAT-2 dual-polarization imagery

Abstract

New regression models for the retrieval of marine wind speeds from RADARSAT-2 dual-polarization images and results of the comparative analysis of these models with the C-band geophysical model function CMOD_IFR2 are presented. In the two new models, synthetic aperture radar (SAR) co-polarization (VV) and cross-polarization (VH) radar cross-sections, instrument noise floor, and antenna beam incidence angle were used as independent variables. In addition, one of the models also included wind direction input. To build and test the empirical relationships between wind speed and RADARSAT-2 parameters, we created a database containing 570 samples of ocean buoy wind speed observations collocated and coincident with the information obtained from SAR images. The models were tested on independent wind speed data reaching up to 40 knots. The CMOD_IFR2 was also tested on the same data. Analysis of the test results proved a higher accuracy of the new regression models, including the model without wind direction, as compared with CMOD_IFR2, which uses wind direction information. This means that the degraded accuracy of the SAR wind retrieval model without input of the wind direction can be compensated for by using cross-polarization backscatter information. The models were validated through current buoy and image data, provided by the quasi-operational Wind Information Processing System (WIPS). The developed models have been integrated into and are currently functioning within WIPS (at the Meteorological Service of Canada).