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Development of Windspeed Retrieval Model using RISAT-1 SAR Cross-Polarized Observations


Affiliations
1 Earth, Ocean, Atmosphere, Planetary Sciences and Applications Area, Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, India
 

In this study, a method for retrieving ocean surface wind speed using C-band cross-polarization SAR observations has been outlined. A linear least square technique has been used to develop a Geophysical Model Function (GMF), C2P. The GMF was derived using NRCS observations from RISAT-1 and wind-speed observations from ASCAT. The correlation between observed and simulated NRCS values obtained from C2P was 0.66, with a negative bias of 0.01 dB and the corresponding ischolar_main mean square difference of 1.13 dB. Subsequently, the developed GMF was tested with 774 RISAT-1 MRS datasets to retrieve wind speed along the Indian coast and also of the tropical cyclone ‘Megh’. The measured intensity and radius of maximum wind speed were 30 m s–1 and 16.65 km respectively. Subsequently, the retrieved wind speed was validated with ASCAT wind-speed observations. The statistical comparison of RISAT-1 and ASCAT observed wind speed showed negative biases of 0.90 and 0.34 m s–1 with the corresponding RMSD of 2.11 and 1.77 m s–1 respectively, for CMOD5.N and C2P. The developed GMF C2P showed 16% more accuracy than that of CMOD5.N.

Keywords

Cross-polarization, Geophysical Model Function, Ocean Surface, Wind Speed Retrieval.
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  • Development of Windspeed Retrieval Model using RISAT-1 SAR Cross-Polarized Observations

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Authors

Jagdish Prajapati
Earth, Ocean, Atmosphere, Planetary Sciences and Applications Area, Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, India
Abhisek Chakraborty
Earth, Ocean, Atmosphere, Planetary Sciences and Applications Area, Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, India
Bipasha Paul Shukla
Earth, Ocean, Atmosphere, Planetary Sciences and Applications Area, Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, India
Raj Kumar
Earth, Ocean, Atmosphere, Planetary Sciences and Applications Area, Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, India

Abstract


In this study, a method for retrieving ocean surface wind speed using C-band cross-polarization SAR observations has been outlined. A linear least square technique has been used to develop a Geophysical Model Function (GMF), C2P. The GMF was derived using NRCS observations from RISAT-1 and wind-speed observations from ASCAT. The correlation between observed and simulated NRCS values obtained from C2P was 0.66, with a negative bias of 0.01 dB and the corresponding ischolar_main mean square difference of 1.13 dB. Subsequently, the developed GMF was tested with 774 RISAT-1 MRS datasets to retrieve wind speed along the Indian coast and also of the tropical cyclone ‘Megh’. The measured intensity and radius of maximum wind speed were 30 m s–1 and 16.65 km respectively. Subsequently, the retrieved wind speed was validated with ASCAT wind-speed observations. The statistical comparison of RISAT-1 and ASCAT observed wind speed showed negative biases of 0.90 and 0.34 m s–1 with the corresponding RMSD of 2.11 and 1.77 m s–1 respectively, for CMOD5.N and C2P. The developed GMF C2P showed 16% more accuracy than that of CMOD5.N.

Keywords


Cross-polarization, Geophysical Model Function, Ocean Surface, Wind Speed Retrieval.

References





DOI: https://doi.org/10.18520/cs%2Fv118%2Fi8%2F1282-1286