CFOSAT SWIM波谱仪中法产品差异性分析

Analysis on differences in CFOSAT SWIM products between Chinese and French sides

中法海洋卫星(China-France Oceanography SATellite,CFOSAT)搭载了世界上第一颗专门探测二维海浪谱的雷达,即SWIM(Surface Waves Investigation and Monitoring)波谱仪。该雷达能通过旋转6个不同波束的方式扫描海面从而得到二维海浪谱信息,并通过控制天线旋转速度来控制沿轨向二维谱的分辨率。中法双方都会发布相同软件处理的波谱仪2级产品,但由于中法双方接收站位置不同、地面数据处理时输入的气象辅助数据源不完全一致,因此双方发布的2级产品有一定差异,这给波谱仪产品的应用带来不确定性。为了明晰不同数据下载源得到的相同版本波谱仪产品之间的差异,选取2024年3月中法相关单位发布的最新版本2级数据,采用5.0 s、3.0 s、1.0 s和0.1 s的时间匹配窗口,获取中法数据不同匹配时间下二维海浪谱3个波浪参数的一致性对比结果。结果表明:有效波高比较稳定,在半个地理单元的空间差别下仍然保持几乎不变的精度;随着匹配时间增大,主波波长和主波波向的差别越来越大,匹配时间为5.0 s时,二者分别达到约21.5 m和46.5°的差异,匹配时间为0.1 s时,其差异很小,表明中法不同地面处理系统输入的气象辅助数据源差异而引起的产品差别可以忽略。

The China-France Oceanography SATellite(CFOSAT)carries the world’s first radar dedicated to the detection of two-dimensional wave spectrum,namely the SWIM(Surface Waves Investigation and Monitoring)spectrometer.The radar can scan the ocean surface by rotating 6 different beams to obtain two-dimensional wave spectrum information and set the resolution of the two-dimensional spectrum along the orbit by controlling the rotation speed of the antenna.China and France release L2 spectrometer products with the same software processing,but because the locations of the receiving stations in China and France are different and the input of meteorological auxiliary data sources during ground data processing are not completely consistent,there are certain differences in the L2 products released by both sides,which brings certain uncertainties to the application of spectrometer products.To clarify the differences between spectrometer products of the same version obtained from different data download sources,the latest version of L2 data released by relevant Chinese and French units in March 2024 is selected.The time-matching windows of 5.0 s,3.0 s,1.0 s and 0.1 s are adopted to obtain the consistency comparison results of the three main wave parameters of the two-dimensional wave spectrum under different matching times.The results show that the significant wave height is relatively stable,and the accuracy remains almost constant under the spatial difference of the maximum half box.With the increase of matching time,the differences of peak wave length and wave direction become larger and larger.When the matching time is 5.0 s,their difference is about 21.5 m and 46.5°,respectively,while the difference is very small when the matching time is 0.1 s,that is,the product difference caused by the difference of meteorological auxiliary data sources input from different ground processing systems in China and France can be ignored.