Perspectives for Future Enhancement of Spaceborne Salinity Observing Capabilities
[25-May-2017] Lee, T.
Presented at the Global Ocean Salinity and the Water Cycle Workshop
The L-band (~ 1.4-GHz) SMOS, Aquarius, and SMAP missions have pioneered salinity remote sensing from space. Sea surface salinity (SSS) products from these missions are significantly improving our understanding of regional SSS variability, the associated ocean dynamics, and the linkages with climate variability and water cycle. The satellite SSS help resolve scales and monitor regions not adequately sampled by in-situ systems. The qualities of the SSS retrievals are continuing to improve. This presentation describes the perspectives for future SSS missions based on community inputs during 2015-2016 to the "2017-2027 Decadal Survey for Earth Science and Applications from Space" organized by the U.S. National Academies. The community inputs recognized three major areas for strengthening spaceborne salinity observing capabilities: (1) improvement of high-latitude SSS accuracy, (2) enhancement of spatial resolution (thereby getting closer to the coasts), and (3) mission continuity. In particular, the need to improve high-latitude satellite SSS stems from the fact that L-band radiometers have poor sensitivity to SSS in cold waters (<5C), and from the importance of high-latitude SSS to deep-water formation, heat and carbon sequestration, and global ocean circulation as well as the related property transports. A measurement concept has been proposed to improve high-latitude SSS by augmenting the L-band with P-band (~0.5 GHz) radiometry because the latter provides nearly three times better sensitivity than L-band for cold waters. Moreover, the dual-frequency L/P-band radiometry can improve the measurements of the thickness of seasonal sea ice, which is becoming more prevalent in the Arctic Ocean as the multi-year sea ice are declining. The enhanced capability to measure seasonal sea-ice thickness complements the existing capability of radar-based measurements of sea-ice thickness that have lower signal-to-noise radio for seasonal than for multi-year sea ice. More accurate sea-ice thickness measurements in turn help improve the correction of sea-ice effects on high-latitude SSS retrieval. The status for the ongoing technological development for the L/P-band radiometer will be discussed.