基于粗糙表面模型的中国近海高度计波形重构与参数反演算法研究

The project will study the current major problem: when the footprint of satellite radar altimeter (altimeter) is in near sea, the returns from the sea is affected and distorted by land returns, and thus measurement error is become much larger,in addition to this, the presicion of measured parameters is low with applying original oceanic models to retrieve and correct these parameters. The case is that these data in near sea is to be used and processed poorly.The poject is to establish sea-land rough surface model to study its electromagnetic reflection characteristics, including backscattering coefficient and return wave power.By backscattering coefficient and return wave power the project will study return waveform types and retrack these waveforms,and retrieve sea parameters. Secondly, the project is to study the distribution of water vapour of the wet troposphere over near China sea by ECMWF and NCEP. By the distribution the project is to correct those retrieved parameters. Finally, the study of those inversed parameters compared with the measured data is performed. These researched results will give some help and basics of near sea parameter retrieval for HY2 altimeter or futural altimeters.

研究当前一个主要问题：卫星雷达高度计(称高度计)足印在近海，海洋回波受陆地影响，测量数据偏差较大，参数反演与校正方法仍采用原来远海海洋模型的算法，结果高度计反演参数精度较差，导致大量近海数据未很好处理和利用。本项目预计在水平方向上建立海陆粗糙表面介质模型来研究海陆混合表面电磁散射特性,主要包括后向散射系数和回波功率。以后向散射系数和回波功率为依据，对高度计近海回波波形分类与重构，进而反演海洋参数。其次利用ECMWF和NCEP数据，研究中国近海湿对流层水汽分布特性并对反演的参数进行校正。最后，研究反演的参数与实测数据对比验证。研究结果为海洋二号卫星雷达高度计近海回波参数反演或未来高度计参数反演提供理论依据和数据支持。

由于高度计接收的近海海面回波受到陆地回波的影响，近海波形被扭曲变形，不再适合海洋模型，结果近海海洋参数海面高度，有效波高和后向散射系数反演结果出现偏差较大，甚至不可信，致使近海大量高度计所测数据不可用。为此，本项目从粗糙海面、陆地电磁散射特性(主要后向散射系数)出发，根据高度计测高原理，仿真了近海回波：噪声区污染型，前沿污染型，后沿污染型。透彻理解了陆地岛屿和人工建筑物对海洋回波影响。提出了近海海洋参数反演新方法-自适应权重重跟踪算法。针对不同污染类型，对近海回波进行权值变化赋值进行重跟踪，反演近海海面高度，有效波高和后向散射系数。反演结果和美国近海浮标数据进行对比分析，证明新算法正确性和精度可接受性，并且能把不可用距离从10km缩短到5km，甚至更短。由此利用提出的自适应权重重跟踪算法对中国近海有效波高和后向散射系数和距离进行了重跟踪，得到了当前中国近海SWH分布，后向散射系数分布。为未来高度计海洋参数反演提供参考，为国民经济提供服务。