| Breaking waves can cause two types of water and gas coexistence on the sea: whitecaps and bubbles in medium and high sea condition.Usually them can be called sea foam.Rainfall and sea surface froth will lead to the attenuation of sea surface backscattering.Rainfall will also absorb and scatter the microwave signal of altimeter,and then the echo signal received by altimeter will be attenuated or even disappear,which will affect the retrieval of altimeter sea surface parameters.Therefore,correcting the influence of froth and rainfall on the retrieval of sea surface parameters is of great significance to improve the accuracy of the retrieval of sea surface parameters.The thesis mainly studies the correction of sea surface parameters of satellite radar altimeter under medium and high sea conditions.Firstly,the data sources used in the thesis are introduced: jason-2 radar altimeter data and NDBC(National Data Buoy Center)buoy data.The data sets used in the thesis are obtained by preprocessing and space-time matching.Secondly,the echo formation principle,echo waveform and echo parameter inversion of radar altimeter are analyzed,and it is pointed out that the echo second-order approximate model can accurately fit the echo waveform in the case of large mispointing angle.In addition,the neural network is applied to the inversion of sea surface wind speed.The Ku-band backscattering coefficient and significant wave height and the C-band backscattering coefficient and significant wave height are used as the input,and the sea surface wind speed is used as the output.Then,the air foam ocean three-layer medium model is established to explore the influence of sea foam on sea surface reflectance,sea surface backscattering coefficient and sea surface wind speed;the existing empirical models of sea surface foam coverage are averaged to get a new model of sea surface foam coverage;a cyclic iterative algorithm is proposed to analyze the backscattering coefficient and sea surface wind speed under the foam effect The correctness and effectiveness of the algorithm are verified by using the data set of matching results;by analyzing the influence of foam on echo,the influence of foam on significant wave height and the correction are studied.Finally,the influence of rainfall on backscattering coefficient and sea surface wind speed inversion is studied,and a new standard relationship of Ku-band and C-band backscattering coefficient is proposed based on Jason-2 altimeter observation data;based on the standard relationship of Ku-band and C-band backscattering coefficient,the double band backscattering coefficient and sea surface wind speed under rainfall effect are corrected by using cyclic iteration algorithm,and the results are compared with the results of other methods The matching result data sets verify the correctness and effectiveness of the algorithm.To sum up,the thesis has a good reference value in the correction of sea surface parameters of satellite radar altimeter under medium and high sea conditions. |
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