数据说明
Aquarius Sea Surface Salinity(SSS)
上传时间：2019-05-22 14:23:15 浏览次数：作者与来源：admin
Sea surface salinity (SSS) is the water salinity close to the ocean's surface. The exact meaning of surface varies according to the measurement method used, generally, it is about 3 millimeters below the sea surface. Psu (Practical salinity units) is the unit of SSS, it represents the amount of salt dissolved in every kilogram (roughly one liter by volume) of seawater.
Unit: psu
Resolution: 1 degree, monthly
Duration: Aug 2011 – Jun 2015
Source: National Aeronautics and Space Agency
Version: V5.0
Processing: Original monthly mean products are shown.
Aquarius is a combined active/passive microwave (L-band) instrument designed to map the salinity of global oceans from space. Aquarius Level 3 sea surface salinity (SSS) rain-flagged standard mapped image data contains gridded 1-degree spatial resolution SSS averaged over daily, 7-days, monthly, and seasonal time scales. This particular data set is the monthly climatology, Ascending rain-flagged rain-flagged sea surface salinity product for version 5.0. Only retrieved values for Ascending passes have been used to create this product. The Aquarius instrument is onboard the AQUARIUS/SAC-D satellite, a collaborative effort between NASA and the Argentinian Space Agency Comision Nacional de Actividades Espaciales (CONAE). The instrument consists of three radiometers in push broom alignment at incidence angles of 29, 38, and 46 degrees incidence angles relative to the shadow side of the orbit. Footprints for the beams are: 76 km (along-track) x 94 km (cross-track), 84 km x 120 km and 96km x 156 km, yielding a total cross-track swath of 370 km. The radiometers measure brightness temperature at 1.413 GHz in their respective horizontal and vertical polarizations (TH and TV). A scatter meter operating at 1.26 GHz measures ocean backscatter in each footprint that is used for surface roughness corrections in the estimation of salinity. The scatter meter has an approximate 390km swath.
The salinity retrieval algorithm retrieves the salinity and wind simultaneously by finding the best fit solution to minimize the difference between the Aquarius data and the model functions：
The weighting factors for the Aquarius data are set according to the expected measurement and modeling uncertainties. We let ΔT be the Noise‐Equivalent‐Delta‐T (NEDT) of radiometer and γp be1.4 times of the radar measurement sensitivity (kpc). The values of NEDT and kpc, a function of signal‐to‐noise ratio, have been precomputed and saved in the Aquarius L2 data files. The value of Δw is 1.5 m s−1, a rather weak constraint because the accuracy of wind speeds is estimated to be about 0.7 m s−1. The value of δ is 0.2, which will constrain the wind direction to be within an RMS deviation of 11° from the NCEP wind direction.
Note that the salinity retrieval algorithm consists of a number of steps that are intended to remove the unwanted sources of radiation (galaxy, sun, moon, and Earth’s atmosphere) in order to obtain just the Earth’s surface emission term.
Known issues
The retrieved data somewhere near continents may be discarded.
Quality of the dataset is highest in open ocean area and will fluctuate in other places.
All the contents of this page are quoted from Barcelona Expert Centre, National Aeronautics and Space Agency. All project documentation and related publications can be found at website: https://podaac.jpl.nasa.gov/aquarius
Unit: psu
Resolution: 1 degree, monthly
Duration: Aug 2011 – Jun 2015
Source: National Aeronautics and Space Agency
Version: V5.0
Processing: Original monthly mean products are shown.
Aquarius is a combined active/passive microwave (L-band) instrument designed to map the salinity of global oceans from space. Aquarius Level 3 sea surface salinity (SSS) rain-flagged standard mapped image data contains gridded 1-degree spatial resolution SSS averaged over daily, 7-days, monthly, and seasonal time scales. This particular data set is the monthly climatology, Ascending rain-flagged rain-flagged sea surface salinity product for version 5.0. Only retrieved values for Ascending passes have been used to create this product. The Aquarius instrument is onboard the AQUARIUS/SAC-D satellite, a collaborative effort between NASA and the Argentinian Space Agency Comision Nacional de Actividades Espaciales (CONAE). The instrument consists of three radiometers in push broom alignment at incidence angles of 29, 38, and 46 degrees incidence angles relative to the shadow side of the orbit. Footprints for the beams are: 76 km (along-track) x 94 km (cross-track), 84 km x 120 km and 96km x 156 km, yielding a total cross-track swath of 370 km. The radiometers measure brightness temperature at 1.413 GHz in their respective horizontal and vertical polarizations (TH and TV). A scatter meter operating at 1.26 GHz measures ocean backscatter in each footprint that is used for surface roughness corrections in the estimation of salinity. The scatter meter has an approximate 390km swath.
The salinity retrieval algorithm retrieves the salinity and wind simultaneously by finding the best fit solution to minimize the difference between the Aquarius data and the model functions：
The weighting factors for the Aquarius data are set according to the expected measurement and modeling uncertainties. We let ΔT be the Noise‐Equivalent‐Delta‐T (NEDT) of radiometer and γp be1.4 times of the radar measurement sensitivity (kpc). The values of NEDT and kpc, a function of signal‐to‐noise ratio, have been precomputed and saved in the Aquarius L2 data files. The value of Δw is 1.5 m s−1, a rather weak constraint because the accuracy of wind speeds is estimated to be about 0.7 m s−1. The value of δ is 0.2, which will constrain the wind direction to be within an RMS deviation of 11° from the NCEP wind direction.
Note that the salinity retrieval algorithm consists of a number of steps that are intended to remove the unwanted sources of radiation (galaxy, sun, moon, and Earth’s atmosphere) in order to obtain just the Earth’s surface emission term.
Known issues
The retrieved data somewhere near continents may be discarded.
Quality of the dataset is highest in open ocean area and will fluctuate in other places.
All the contents of this page are quoted from Barcelona Expert Centre, National Aeronautics and Space Agency. All project documentation and related publications can be found at website: https://podaac.jpl.nasa.gov/aquarius
