Marine & Environmental Sciences Faculty Articles

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

ORCID

0000-0001-6519-1547

Document Type

Article

Publication Title

Bulletin of the American Meteorological Society

ISSN

1520-0477

Publication Date

2016

Abstract

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 100x100 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 comparing 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.

DOI

10.1175/BAMS-D-15-00032.1

Volume

97

Issue

8

First Page

1391

Last Page

1407

Comments

©2016 American Meteorological Society

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Peer Reviewed

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