Preliminary validation of SMOS sea surface salinity measurements in the South China Sea

• Published in: Chinese journal of oceanology and limnology 2015-01, Vol.33 (1), p.262-271
• Main Author: 任永政 董庆 贺明霞
• Format: Article
• Language: English
• Subjects: Accuracy; autumn; Bias; Earth and Environmental Science; Earth Sciences; Environmental conditions; environmental factors; Environmental impact; Expeditions; In situ measurement; Marine; Oceanography; Physics; radio; Radio frequency; Salinity; Salinity effects; Sea surface; Sea surface temperature; Soil moisture; Soil Moisture and Ocean Salinity satellite; Structural basins; Surface roughness; Surface salinity; Surface temperature; surface water temperature; Surface wind; wind; 中国南海; 半经验模型; 数据检索; 海洋表面; 海面粗糙度; 现场测量; 盐度测量; 验证
• ISSN: 0254-4059; 2096-5508; 1993-5005; 2523-3521
• DOI: 10.1007/s00343-014-3338-5

The SMOS (soil moisture and ocean salinity) mission undertaken by the European Space Agency (ESA) has provided sea surface salinity (SSS) measurements at global scale since 2009. Validation of SSS values retrieved from SMOS data has been done globally and regionally. However, the accuracy of SSS measurements by SMOS in the China seas has not been examined in detail. In this study, we compared retrieved SSS values from SMOS data with in situ measurements from a South China Sea (SCS) expedition during autumn 2011. The comparison shows that the retrieved SSS values using ascending pass data have much better agreement with in situ measurements than the result derived from descending pass data. Accuracy in terms of bias and root mean square error (RMS) of the SSS retrieved using three different sea surface roughness models is very consistent, regardless of ascending or descending orbits. When ascending and descending measurements are combined for comparison, the retrieved SSS using a semi-empirical model shows the best agreement with in situ measurements, with bias −0.33 practical salinity units and RMS 0.74. We also investigated the impact of environmental conditions of sea surface wind and sea surface temperature on accuracy of the retrieved SSS. The SCS is a semi-closed basin where radio frequencies transmitted from the mainland strongly interfere with SMOS measurements. Therefore, accuracy of retrieved SSS shows a relationship with distance between the validation sites and land.