摘要
The wind retrieval performance of HY-2 A scanning scatterometer operating at Ku-band in HH and VV polarizations has been well evaluated in the wind speed range of 0–25 m s^-1.In order to obtain more accurate ocean wind field,a potential extension of dual-frequency(C-band and Ku-band)polarimetric measurements is investigated for both low and very high wind speeds,from 5 to 45 m s^-1.Based on the geophysical model functions of C-band and Ku-band,the simulation results show that the polarimetric measurements of Ku-band can improve the wind vector retrieval over the entire scatterometer swath,especially in nadir area,with the wind direction root-mean-square error(RMSE)less than 12?in the wind speed range of 5–25 m s^-1.Furthermore,the results also show that C-band cross-polarization plays a very important role in improving the wind speed retrieval,with the wind speed retrieval accuracy better than 2 m s^-1 for all wind conditions(0–45 m s^-1).For extreme winds,the C-band HH backscatter coefficients modeled by CMOD5.N(H)and the ocean co-polarization ratio model at large incidence are used to retrieve sea surface wind vector.This result reveals that there is a big decrease of wind direction retrieval RMSE for extreme wind fields,and the retrieved result of C-band HH polarization is nearly the same as that of C-band VV polarization for low-to-high wind speed(5–25 m s^-1).Thus,to improve the wind retrieval for all wind conditions,the dual-frequency polarimetric scatterometer with C-band and Ku-band horizontal polarization in inner beam,and C-band horizontal and Ku-band vertical polarization in outer beam,can be used to measure ocean winds.This study will contribute to the wind retrieval with merged satellites data and the future spaceborne scatterometer.
The wind retrieval performance of HY-2 A scanning scatterometer operating at Ku-band in HH and VV polarizations has been well evaluated in the wind speed range of 0–25 m s-1. In order to obtain more accurate ocean wind field, a potential extension of dual-frequency(C-band and Ku-band) polarimetric measurements is investigated for both low and very high wind speeds, from 5 to 45 m s-1. Based on the geophysical model functions of C-band and Ku-band, the simulation results show that the polarimetric measurements of Ku-band can improve the wind vector retrieval over the entire scatterometer swath, especially in nadir area, with the wind direction root-mean-square error(RMSE) less than 12? in the wind speed range of 5–25 m s-1. Furthermore, the results also show that C-band cross-polarization plays a very important role in improving the wind speed retrieval, with the wind speed retrieval accuracy better than 2 m s-1 for all wind conditions(0–45 m s-1). For extreme winds, the C-band HH backscatter coefficients modeled by CMOD5.N(H) and the ocean co-polarization ratio model at large incidence are used to retrieve sea surface wind vector. This result reveals that there is a big decrease of wind direction retrieval RMSE for extreme wind fields, and the retrieved result of C-band HH polarization is nearly the same as that of C-band VV polarization for low-to-high wind speed(5–25 m s-1). Thus, to improve the wind retrieval for all wind conditions, the dual-frequency polarimetric scatterometer with C-band and Ku-band horizontal polarization in inner beam, and C-band horizontal and Ku-band vertical polarization in outer beam, can be used to measure ocean winds. This study will contribute to the wind retrieval with merged satellites data and the future spaceborne scatterometer.
基金
supported by the National Key R&D Program of China (No. 2016YFC1401006)
the National Natural Science Foundation of China (Nos. 51279186, 51479183 and 41676169)
the National Program on Key Basic Research Project (No. 2011CB013704)
the 111 Project (No. B14028)
the Marine and Fishery Information Center Project of Jiangsu Province (No. SJC2014 110338)
