Satellite and In Situ Salinity: Understanding Near-Surface Stratification and Subfootprint Variability

Jacqueline Boutin (1) , Yi Chao (2, 3) , William E. Asher (4) , Thierry Delcroix (5) , D. Drucker (6) , Kyla Drushka (4) , Nicolas N. Kolodziejczyk (1) , Tong Lee (7) , Nicolas Reul (8) , Gilles Reverdin (1) , J. Schanze (9) , A. Soloviev (10) , Linwen Yu (11) , J. Anderson (6) , Ludovic Bruckert (12) , Emmanuel P. Dinnat (13) , Adrea Santos-Garcia (14) , L. Jones (14) , Christophe Maes (15) , Thomas Meissner (16) , W. Tang (7) , Nadya Vinogradova (17) , Brian Ward (18)

1 IPSO - Interactions et Processus au sein de la couche de Surface Océanique
2 JIFRESSE - UCLA Joint Institute for Regional Earth System Science and Engineering
3 Remote Sensing Solutions
4 University of Washington [Seattle]
5 LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
6 School of Oceanography [Seattle]
7 JPL - Jet Propulsion Laboratory
8 IFREMER - Institut Français de Recherche pour l'Exploitation de la Mer
9 ESR - Earth and Space Research Institute [Seattle]
10 NSU - Nova Southeastern University
11 WHOI - Woods Hole Oceanographic Institution
12 USRA - Universities Space Research Association [Washington]
13 GSFC Cryospheric Sciences Laboratory
14 Electrical and Computer Engineering Department [Orlando]
15 LPO - Laboratoire de physique des océans
16 RSS - Remote Sensing Systems [Santa Rosa]
17 AER - Atmospheric and Environmental Research, Inc.
18 NUI Galway - National University of Ireland [Galway]

Remote sensing of salinity using satellite-mounted microwave radiometers provides new perspectives for studying ocean dynamics and the global hydrological cycle. Calibration and validation of these measurements is challenging because satellite and in situ methods measure salinity differently. Microwave radiometers measure the salinity in the top few centimeters of the ocean, whereas most in situ observations are reported below a depth of a few meters. Additionally, satellites measure salinity as a spatial average over an area of about 100 × 100 km². In contrast, in situ sensors provide pointwise measurements at the location of the sensor. Thus, the presence of vertical gradients in, and horizontal variability of, sea surface salinity complicates comparison of satellite and in situ measurements. This paper synthesizes present knowledge of the magnitude and the processes that contribute to the formation and evolution of vertical and horizontal variability in near-surface salinity. Rainfall, freshwater plumes, and evaporation can generate vertical gradients of salinity, and in some cases these gradients can be large enough to affect validation of satellite measurements. Similarly, mesoscale to submesoscale processes can lead to horizontal variability that can also affect comparisons of satellite data to in situ data. Comparisons between satellite and in situ salinity measurements must take into account both vertical stratification and horizontal variability.

Domaines: Météorologie; Océanographie

Jacqueline Boutin, Yi Chao, William E. Asher, Thierry Delcroix, D. Drucker, et al.. Satellite and In Situ Salinity: Understanding Near-Surface Stratification and Subfootprint Variability. Bulletin of the American Meteorological Society, 2016, 97 (8), pp.1391-1407. ⟨10.1175/BAMS-D-15-00032.1⟩. ⟨hal-01360859⟩