SSS SMOS/SMAP OI L4 maps

15 years of L-Band remote sensing Sea Surface Salinity (SSS) measurements have proven the capability of satellite SSS to resolve large scale to mesoscale SSS features in tropical to subtropical ocean. In mid to high latitude, L-Band measurements still suffer from large scale and time varying biases. Here, a simple method is proposed to mitigate the large scale and time varying biases. First, in order to estimate these biases, an Optimal Interpolation (OI) using a large correlation scale is used to map SMOS and SMAP L3 products and is compared to equivalent mapping of in situ observations. Then, a second mapping is performed on corrected SSS at scale of SMOS/SMAP resolution (~45 km). This procedure allows to correct and merge both products, and to increase signal to noise ratio of the absolute SSS estimates. Using thermodynamic equation of state (TEOS-10), the resulting L4 SSS product is combined with microwave satellite SST products to produce sea surface density and spiciness, useful to fully characterize the surface ocean water masses. The new L4 SSS products is validated against independent in situ measurements from low to high latitudes. The L4 products exhibits a significant improvement in mid-and high latitude in comparison to the existing SMOS and SMAP L3 products.

十年L波段（L-Band）遥感海表盐度（Sea Surface Salinity, SSS）观测数据已证实，卫星遥感海表盐度可解析热带至亚热带洋域内从大尺度到中尺度的海表盐度特征。在中高纬度区域，L波段观测仍存在大尺度且随时间变化的偏差。本文提出一种简易方法以抑制此类大尺度时变偏差：首先，为估算该类偏差，采用大相关尺度的最优插值（Optimal Interpolation, OI）方法对土壤湿度与海洋盐度卫星（SMOS）、土壤湿度主动被动卫星（SMAP）的L3级产品开展空间制图，并将结果与原位观测的等效制图结果进行对比；随后，以SMOS/SMAP的分辨率（约45千米）为尺度，对校正后的海表盐度开展第二次制图。该流程可实现两款产品的校正与融合，并提升绝对海表盐度估算结果的信噪比。利用热力学状态方程（TEOS-10），将所得L4级海表盐度产品与微波卫星海表温度（Sea Surface Temperature, SST）产品相结合，可生成海表密度与海水尖度（spiciness），用于全面表征表层海水团属性。本新型L4级海表盐度产品通过覆盖低纬度至高纬度的独立原位观测数据完成验证。相较于现有SMOS与SMAP的L3级产品，该L4级产品在中高纬度区域展现出显著性能提升。然而在北冰洋海域，L波段海表盐度反演面临的海冰污染、冷水环境下灵敏度偏低等问题，仍对L波段海表盐度数据的优化改进构成挑战。

搜集汇总

背景与挑战

背景概述

该数据集是一个L4级海表盐度（SSS）产品，结合了SMOS和SMAP卫星的观测数据，时间覆盖2010年至2024年，全球范围从89°N到89°S。它采用最优插值方法校正了卫星数据中的大尺度和时间变化偏差，并整合海表温度数据以生成海表密度和spiciness，旨在提高中高纬度地区的精度，但在北极地区仍受海冰污染和低温敏感性问题限制。