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JPL SMAP Level 2B Near Real-time CAP Sea Surface Salinity V4.3 Validated Dataset

This is the PI-produced JPL SMAP-SSS V4.3, level 2B NRT CAP, validated sea surface salinity (SSS) and extreme winds orbital/swath product from the NASA Soil Moisture Active Passive (SMAP) observatory available in near real-time with a latency of about 6 hours. It is based on the Combined Active-Passive (CAP) retrieval algorithm developed at JPL originally in the context of Aquarius/SAC-D and now extended to SMAP. Improvements with V4.3 include: 1) New residual TB calibration which removes the ascending/descending bias issue observed for version 4.2; 2) Slightly modified criteria for aggregation from L2B to L3 based on TB for V-pol minus TB for H-pol. The JPL SMAP-SSS L2B CAP NRT product includes data for a range of parameters: derived SMAP sea surface salinity, SSS uncertainty and wind speed/direction data for extreme winds, brightness temperatures for each radiometer polarization, ancillary reference surface salinity, ice concentration, wind and wave height data, quality flags, and navigation data. Each data file covers one 98-minute orbit (15 files per day). Data begins on April 1,2015 and is ongoing, with a 6 hour latency in processing and availability. Observations are global in extent and provided at 25km swath grid with an approximate spatial resolution of 60 km.The SMAP satellite is in a near-polar orbit at an inclination of 98 degrees and an altitude of 685 km. It has an ascending node time of 6 pm and is sun-synchronous. With its 1000km swath, SMAP achieves global coverage in approximately 3 days, but has an exact orbit repeat cycle of 8 days. On board Instruments include a highly sensitive L-band radiometer operating at 1.41GHz and an L-band 1.26GHz radar sensor providing complementary active and passive sensing capabilities. Malfunction of the SMAP scatterometer on 7 July, 2015, has necessitated the use of collocated wind speed for the surface roughness correction required for the surface salinity retrieval.

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