南海区域Aquarius遥感海表盐度V4产品精度探讨

On the Performance of Aquarius Sea Surface Salinity V4 Product in the South China Sea

Aquarius/SAC-D卫星,以实现海表盐度(sea surface salinity,SSS)全球遥感观测为目标,经过算法的不断改进,迄今已发布第4版产品(V4).已有的检验研究表明V1.3产品在全球最大的边缘海——中国南海的精度并未达到该产品的目标精度,主要原因是射频干扰(radio frequency interference,RFI)的影响.为探讨新版数据在中国南海的精度,通过比较南海走航盐度、Argo浮标盐度与Aquarius遥感SSS V4及旧版产品的差异,发现Aquarius遥感SSS V4与走航盐度及Argo浮标盐度的均方根误差(RMSE)分别为0.47和0.73,V4产品整体表现优于V3及之前的版本,特别是在南海北部近岸高RFI海域,V4产品的偏差也小于V3,说明V4产品中RFI的影响相较于V3产品在一定程度上得到了有效的去除.同时,分析表明Aquarius遥感SSS V4产品所揭示的南海SSS空间分布与季节变动特征,与前人通过实测调查获得的结论基本一致.

Previous studies have demonstrated that the accuracy of Aquarius sea surface salinity （SSS）V1.3 product in the South China Sea （SCS）,one of the largest marginal seas in the world,is far from being satisfied.It has been suggested to mainly result from radio frequency interference （RFI）from lands surrounding the SCS.It is not clear yet if there is any improvement in the newest SSS product,i.e.V4.Here in this study,we compared the V4 SSS product of Aquarius with concurrent in situ measured salinity data （both underway mapping and Argo floats data）in the South China Sea.Root mean square errors of 0.47 and 0.73,for underway and Argo data,respectively,were obtained,suggesting evident improvements of V4 over V3 and V1.3.Improvements were particularly seen in the northern SCS,where the influence of RFI was thought to be severe,suggesting that the removal of RFI in V4 was indeed effi-cient.In addition,the spatio-temporal features and seasonal dynamics seen from the V4 SSS were in general consistent with historical in situ reports.