WANG Rui,
SHI Shun-Wen,
YAN Wei et al
.2014.Sea surface wind retrieval from polarimetric microwave radiometer in typhoon area.Chinese Journal Of Geophysics,57(3): 738-751,doi: 10.6038/cjg20140305
Sea surface wind retrieval from polarimetric microwave radiometer in typhoon area
WANG Rui1, SHI Shun-Wen2, YAN Wei1, LU Wen1
1. College of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China;
2. College of Basic Education for Commanding Officers, PLA University of Science and Technology, Nanjing 211101, China
As a new technology in the field of passive remote sensing, polarimetric microwave radiometer can provide wind direction products as well as wind speed. In the past, the sea surface wind vector retrievals from polarimetric microwave radiometer are only in clear sky conditions. By analyzing the distribution characteristics of polarimetric microwave radiometer brightness temperature combined with wind vector distribution characteristics in typhoon area, we confirmed that polarimetric microwave radiometer is capable of observing sea surface wind under inclement weather conditions such as typhoon. Through sensitivity analysis experiment, we choose the low frequencies group (6.8 GHz and 10.7 GHz) to use in sea surface wind vector retrievals. Sea surface wind speed retrieval uses the multiple linear regression algorithm based on statistics, and other physical quantities like sea surface temperature, atmospheric water vapor content, cloud liquid water content and precipitation intensity should be retrieved at the same time, preparing for sea surface wind direction retrieval. Sea wind direction retrieval uses the physical statistical method-maximum likelihood estimation, learned from scatterometer. By adding precipitation influence in polarimetric microwave radiative Forward Model, which comes from Naval Research Laboratory for the U.S. Navy, and designing environmental influence empirical correction function for the third and fourth Stokes channels, we not only achieved wind direction retrieval but also reduced retrieval errors. Through numerical calculation of sea wind vector retrievals under Rananim, we verified the feasibility of the retrieval algorithm, and analyzed the spatial distribution characteristics of wind speed and direction retrieval errors. Comparing sea surface wind vector retrieval results with scatterometer wind field products from every typhoon process of the year 2004, the root mean square error is 1.64 m·s-1 for sea surface wind speed and 18.02°for sea surface wind direction.
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