Research Of The Accuracy Improvement Of Sea Surface Wind Speed Estimation From Space-based Lidar Measurements

Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) is onboard on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), which data can be used to get sea surface wind speed with high resolution. In order to improve the accuracy of wind speed measurements, eight months (January, April, July and October,2007and January, April, July and October,2008) CALIPSO lidar data are studied. The sea surface lidar backscatter signal is get form the version3.01lidar level1data. CALIPSO level2data with5km horizontal resolution provide aerosols optical depth data and cloud optical thickness data, which can be used to calculate the two-way atmospheric transmittance of lidar signal. Both depolarization correction method and formula correction method are used to correct the contributions from whitecaps and subsurface backscattering. System deviation is eliminated by calculating location seasonal correction factors. This information can be used to get a more accurate relationship between wind driven wave slope variance and sea surface wind speed, combing with wind speed provided by Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) since the two satellites are both in A-train. The accuracy of high resolution sea wind speed is improved.More accurate sea surface lidar signals can be got by using the accurate determination method of sea surface level bin. Collocated AMSR-E version7sea surface wind speed data are used as the real data. In order to expand the amount of data, we do not eliminate cloudy sea surface lidar signals and get the related signals by analyzing two parameters—Integrated Backscatter Coefficient (IBC) and the two-way atmospheric transmission(T2). After the corrections of two-way atmospheric transmittance, whitecap, sub-surface and location, we get the sea surface lidar backscatter signals which only caused by sea surface wind. For the data with3degree satellite nadir angle, a new relationship between wave slope variance and sea surface backscatter signal is presented.The new method of CALIPSO sea surface backscattering extraction and choosing method, two-way atmospheric transmittance and lidar correction are verified by using Hu’s and Jia’s relationship. The difference between CALIPSO5km mean wind speed and AMSR-E sea surface wind speed is calculated. The bias difference reduces to-0.01m/s,the RMS reduces to0.96m/s and the correlation coefficient is about0.95. Nonlinear fit the relationship between CALIPSO532nm sea surface backscatter and AMSR-E wind speed with all available data, but not only for lowest aerosol loadings (cleanest atmosphere, with smallest2%IBC). Mainly modify the high wind speed area. Derive the wind speed from CALIPSO532nm lidar single shot and5km mean signals by using the new relationship and the wind difference results are better than Hu’s and Jia’s relation. What’s more, the new relationship’s application is verified by other three special situations’ data—the data when CALIPSO nadir angle changing to3degree, the data of CALIPSO daytime with more complicated atmosphere environment and CALIPSO1064nm channel data with lower signal-to-noise ratio.