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RSS (V5) |
JPL (V5) |
Level 1B (processed at sensor level) |
- Noise for SMAP Effective Field of View is 2 PSU
- Useless for most ocean applications
- Far sidelobe correction is applied
- This is comparable to a "land correction"
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- Pre-processes collocations of model sea surface salinity, sea surface temperature, significant wave height and SMAP data
- Version 5 is "based on the newly released SMAP V5 Level-1 Brightness Temperatures (TB). An enhanced calibration methodology has been applied… which improves absolute radiometric calibration and reduces the biases between ascending and descending passes."
- Look-Up Table Approach
- This is consistent with other empirical data-driven calibration done at Level 1B
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Level 2 (swath) |
- Resample using Backus-Gilbert Optimum Interpolation (BG-OI) onto fixed ¼-degree Earth grid
- 40-km product
- BG-OI reduces noise to 1 PSU over the open ocean; however, BG-OI gives poor results close to land
- No Q/C applied but quality info is included in L2 files
- 70-km product
- Employ next-neighbor averaging of the 40-km product to reduce noise to 0.5 PSU
- This "smearing out" is done instead of BG-OI resampling of the 70-km footprint
- Extensive Q/C filters out questionable data
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- Resample onto fixed ¼-degree Earth grid
- 60-km product
- JPL spatially averages the native 40-km retrieval to a larger footprint to reduce data noise
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Level 3 (gridded) |
- For each grid size (i.e., 40-km and 70-km), two products are created: 8-day and monthly averages
- 40-km products
- Some basic Q/C (sun-glint, high galaxy, high wind, etc.) is applied
- 70-km products
- Extensive Q/C at Level 2 (see above) has filtered out questionable data
- Monthly averaging reduces noise to 0.2 PSU (science goal)
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- Time-averaged over one month to reduce noise to 0.2 PSU (mission requirement)
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Next Steps |
- Our next version (RSS V5) will have formal uncertainty estimates including errors from land contamination in Level-2C and all Level-3 products.
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- We are working to improve our data screening… that is filtering implemented between Level-2 and Level-3 products.
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