降雨条件下HY-2高度计有效波高反演技术研究

HY-2 altimeter is the first satellite-borne radar altimeter used in oceanographic observation. Since it was launched in 2011, HY-2 altimeter has provided a lot of sea surface observation data for researchers, including sea-surface height, wind speed and significant wave height. However, those data are not valid for rainy conditions. In addition, the significant wave height inversion in rainy conditions has not been reported. To solve the above problem, based on the Brown equation we propose to develop a new echo waveform modal by introducing the rainy parameters which affect the echo wave form of altimeter.. In this project, a significant wave height inversion algorithm for HY-2 altimeter in rainy conditions is developed. Firstly, based on the HY-2 data, rain and no rain dataset are established. Secondly, significant wave height inversion algorithm are performed in the weak rainfall and strong rainfall conditions, respectively. Then, algorithm is verified and optimized by buoy data and TRMM precipitation radar data. Finally, study of significant wave height inversion in rainy conditions is completed. . The project presented here may expand the applied range of significant wave height inversion technique with HY-2 altimeter, develop an inversion algorithm with independent intellectual property rights, and realize the 24-hour data collection of oceanic environmental parameters from HY-2 radar altimeter with high accuracy.

HY-2 高度计是我国第一个专用于海洋科学研究的星载雷达高度计。自2011年发射以来，HY-2高度计提供了大量的海面观测数据，包括海表面高度、风速和有效波高等。但是，对于降雨情况的观测数据是不可用的。而降雨条件下有效波高的反演算法还未见报道，本项目拟根据Brown方程，引入影响高度计回波的各降雨参量，发展新的回波模型，试图解决这一问题。. 本项目针对HY-2高度计开展降雨条件下高度计有效波高反演算法研究。首先，基于HY-2数据分别建立非降雨和降雨数据集；其次，分别开展在强、弱降雨条件下的有效波高反演算法研究，再利用浮标数据及TRMM测雨雷达数据对强、弱两种降雨条件下的算法进行检验和优化；最后，形成降雨条件下的高度计有效波高反演算法。. 本项目的完成将扩展HY-2 高度计反演算法应用范围，形成具有自主知识产权的反演算法，实现高精度、“全天候” 卫星高度计海洋环境参数信息提取。

降雨对微波信号具有衰减作用，从而导致卫星雷达高度计有效波高测量精度下降。课题组基于浮标数据对高度计有效波高精度进行验证，结果表明即便降雨情况下，依然存在精度满足要求的有效波高数据，相对偏差小于5%的数据比例，Ku波段为19.54%，C波段为14.94%。采用本项目提出的“双频法”可以提取降雨条件下有效波高，提取波高IMPs（the Improvement Percentages）为71.64%。以浮标波高为真值，开展了Ku和C波段有效波高校正工作，结果表明二次校正结果优于一次校正，对Ku波段进行二次校正，相对偏差从40.51%提高至37.43%。此外还开展了基于校正辐射计的降雨率估计算法研究，利用本研究的算法估计降雨率可以有效避免波束填充效应，相对偏差可达42.33%。以上工作均可用于HY—2卫星雷达高度计。