Remote Sensing of Sea Surface Salinity

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Dr. David Le Vine

NASA Goddard Space Flight Center

Monday February 11, 2019, 12:00-1:00 PM

ESSIC Conference Room 4102, 5825 University Research Ct, College Park, MD 20740

Abstract:

Salinity of ocean water is important for understanding ocean circulation and climate. Salinity together with temperature determine water density, and the density driven ocean circulation (thermohaline circulation) moves vast amounts of water and heat. Salinity also reflects the balance of evaporation and precipitation, and knowledge of salinity is helpful for understanding the role of the oceans in the global hydrologic cycle. Changes in salinity change the conductivity of seawater and affects the emissivity at the water surface. The change in thermal emission is sufficiently strong in the long wavelength microwave portion of the spectrum (L-band) to be measured with modern spaceborne radiometers. This is a challenging measurement. Not only is the dynamic range of the signal small (several Kelvin) but there are competing factors such as the effects of surface roughness and radiation from the atmosphere that tend to mask the desired signal. But the measurement can be made and with an accuracy appropriate for meaningful science applications. This has been demonstrated by Aquarius and SMOS, and research is underway to develop a salinity product from the radiometer on SMAP. Aquarius was unique among these L-band sensors in that it was designed specifically to monitor sea surface salinity, and included a scatterometer to correct for roughness, a polarimetric channel to help correct for Faraday rotation, and fast sampling to help mitigate man made interference (RFI). The global salinity maps from space reflect the balance between evaporation and precipitation expected in salinity climatology, but they also show dynamic features such as changes in the Bay of Bengal in response to the Indian Monson and inter-annual changes in the mean salinity field. Planning has begun on the next generation of salinity sensing from space with an eye toward improved spatial resolution and improved performance in cold water.

Bio-sketch:

David Le Vine works in the Earth Sciences Division at NASA’s Goddard Space Flight Center where he does research to develop techniques for microwave remote sensing of the environment from space. His research has focused on passive remote sensing at the long wavelength end of the microwave spectrum (e.g. L-band) with applications to remote sensing of soil moisture and sea surface salinity. He was Deputy Principal Investigator for AQUARIUS, a NASA Earth System Science Pathfinder (ESSP) mission to measure sea surface salinity, and is currently a member of the Science Team for NASA’s Soil Moisture Active Passive (SMAP) mission and a member of the Quality Working Group supporting ESA’s Soil Moisture and Ocean Salinity (SMOS) mission. Dr. Le Vine is a fellow of the IEEE and a member of the Geoscience and Remote Sensing Society (GRSS) and Antennas and Propagation Society. He is the recipient of the IEEE/GRSS Distinguished Achievement award and Golden Florin award for contributions to microwave radiometry. His service includes the GRSS Administrative Committee (AdCom), the National Academy of Science Committee on Radio Frequency (CORF) and the IEEE Fellows Committee.

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