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Impact of sea surface temperature on sea surface salinity retrieval by SMOS microwave radiometer

  • role： First author第一作者
  • Affiliation：

    State Key Laboratory of Satellite Ocean Environment Dynamics (SOED), Second Institute of Oceanography, Hangzhou 310012, China

  • Email：jxc1993@126.com
  • Introduction：金旭晨(1993—　)，男，硕士研究生，研究方向为海洋遥感。E-mail：jxc1993@126.com
Xuchen JIN,  
  • role： Corresponding author通信作者
  • Affiliation：

    State Key Laboratory of Satellite Ocean Environment Dynamics (SOED), Second Institute of Oceanography, Hangzhou 310012, China

  • Email：zhuqiankun@sio.org.cn
  • Introduction：朱乾坤(1974—　)，男，高级工程师，研究方向为遥感技术。E-mail：zhuqiankun@sio.org.cn
Qiankun ZHU*,  
  • Affiliation：

    State Key Laboratory of Satellite Ocean Environment Dynamics (SOED), Second Institute of Oceanography, Hangzhou 310012, China

Delu PAN,  
  • Affiliation：

    State Key Laboratory of Satellite Ocean Environment Dynamics (SOED), Second Institute of Oceanography, Hangzhou 310012, China

Fang GONG,  
  • Affiliation：

    State Key Laboratory of Satellite Ocean Environment Dynamics (SOED), Second Institute of Oceanography, Hangzhou 310012, China

Xianqiang HE

resumen

Global sea surface salinity (SSS) is retrieved using satellite microwave radiometers, Currently. However, SSS remote sensing with an L-band radiometer is still challenging due to the low sensitivity of its brightness temperature to SSS variation. Results show that the sensitivities of vertically (Tv) and horizontally (Th) polarized brightness temperature range from 0.4 K/psu to 0.8 K/psu and from 0.2 K/psu to 0.6 K/psu, respectively, at different observing angles and sea surface temperatures (SSTs). Hence, high-accuracy measurements are required. However, the quantitative effect of Sea Surface Temperature (SST) on the satellite retrieval of SSS remains unknown. In this study, we investigate the effect of SST on the accuracy of salinity retrieval from the Soil Moisture and Ocean Salinity (SMOS). The dielectric constant model proposed by Klein and Swift has been used to estimate theTv and Th of a flat sea water surface at L-band and obtain the derivatives of Tv and Th as a function of SSS to show the relative sensitivity at different incident angles (12.5° and 42.5°). Moreover, the Generalized Additive Model (GAM) and the Partial Least Squares (PLS) regression method were used to investigate the effect of SST on the accuracy of salinity retrieval from the SMOS. Furthermore, SMOS data are compared with Argo data to assess the quality of satellite-derived SSS data at different SSTs by calculating the root-mean-square error (RMSE) of two regions of the Pacific Ocean far from land and ice. Results show that satellite-measured brightness temperature has high sensitivity to SSS variation and good accuracy of SSS retrieval with high SST. For most open oceans where surface salinity is typically greater than 32 psu, the sensitivity is approximately 0.2–0.25 K/psu for Tv and Th when the SST is 5 ℃, and the brightness temperature is more sensitive to the SSS for Tv than Th with increasing SST. When the SST increases to 30 ℃, the sensitivity is approximately 0.8 K/psu for Tv. Moreover, the RMSEs of SMOS-derived SSS data are approximately 0.9, 0.7, and 0.4 psu in regions of the Pacific Ocean where the SSTs are approximately 16 ℃, 23 ℃, and 30 ℃, respectively. Results of the GAM and the PLS model indicate that satellite-measured brightness temperature highly correlates with in situ SSS at high SSTs. In addition, validation results of Argo data suggest that water temperature significantly affectsSSS retrieval accuracy and that accurate SSS retrieval can be achieved at high SSTs. These results indicate that SST can significantly influence the retrieval accuracy of SSS. Hence, the development of a new SSS retrieval algorithm that adapts to low SSTs is necessary.

palabra clave

sea surface salinity;satellite remote sensing;water temperature;retrieval accuracy

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