A performance evaluation of remotely sensed sea surface salinity products in combination with other surface measurements
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A performance evaluation of remotely sensed sea surface salinity products in combination with other surface measurements in reconstructing three-dimensional salinity fields CHEN Jian1*, YOU Xiaobao1, XIAO Yiguo1, ZHANG Ren2, WANG Gongjie2, BAO Senliang2 1 Beijing Institute of Applied Meteorology, Beijing 100029, China 2 Institute of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China
Received 6 May 2016; accepted 17 January 2017 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2017
Abstract
Several remotely sensed sea surface salinity (SSS) retrievals with various resolutions from the soil moisture and ocean salinity (SMOS) and Aquarius/SAC-D missions are applied as inputs for retrieving salinity profiles (S) using multilinear regressions. The performance is evaluated using a total root mean square (RMS) error, different error sources, and the feature resolutions of the retrieved S fields. In the mixed layer of the salinity, the SSS-S regression coefficients are uniformly large. The SSS inputs yield smaller RMS errors in the retrieved S with respect to Argo profiles as their spatial or temporal resolution decreases. The projected SSS errors are dominant, and the retrieved S values are more accurate than those of climatology in the tropics except for the tropical Atlantic, where the regression errors are abnormally large. Below that level, because of the influence of a sea level anomaly, the areas of high-accuracy S values shift to higher latitudes except in the high-latitude southern oceans, where the projected SSS errors are abnormally large. A spectral analysis suggests that the CATDS-0.25° results are much noisier and that the BEC-L4-0.25° results are much smoother than those of the other retrievals. Aquarius-CAP-1° generates the smallest RMS errors, and Aquarius-V2-1° performs well in depicting large-scale phenomena. BEC-L3-0.25°, which has small RMS errors and remarkable mesoscale energy, is the best fit for portraying mesoscale features in the SSS and retrieved S fields. The current priority for retrieving S is to improve the reliability of satellite SSS especially at middle and high latitudes, by developing advanced algorithms, combining both sensors, or weighing between accuracy and resolutions. Key words: soil moisture and ocean salinity, Aquarius, sea surface salinity, vertical retrieval, feature resolution Citation: Chen Jian, You Xiaobao, Xiao Yiguo, Zhang Ren, Wang Gongjie, Bao Senliang. 2017. A performance evaluation of remotely sensed sea surface salinity products in combination with other surface measurements in reconstructing three-dimensional salinity fields. Acta Oceanologica Sinica, 36(7): 15–31, doi: 10.1007/s13131-017-1079-y
1 Introduction Two innovative satellite missions have recently been designed to measure sea surface salinity (SSS) from space: SMOS (soil moisture and ocean salinity) and Aquarius/SAC-D. The SMOS satellite was launched in November 2009 (Kerr et al., 2010) and is the second earth explorer opportunity mis
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