Better constraint of the western boundary current fronts #1992
Description
Better constraint of the western boundary current fronts
Description
Develop a mechanism to improve the treatment of western boundary current (WBC) regions (Gulf Stream, Kuroshio, etc.) by applying spatially-varying altimeter observation errors in regions of high kinetic energy (KE).
While the background error currently captures the location of the fronts (large variability aligns well with energetic WBC regions), it is not sufficient to tightly constrain the fronts. Additional constraint through spatially-aware observation error specification may help improve the relocation of the currents and reduce downstream biases.
Tasks
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Generate a WBC mask based on the kinetic energy (KE) field.
- Source of KE is not fixed yet: Could be derived from an observation-based product (e.g., OSCAR) or from the background.
- Compute KE and apply a threshold to isolate energetic regions.
- Produce a (binary?) mask on the model grid.
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Update altimeter observation errors so they are reduced within masked regions.
- Implement a tunable scaling factor for error reduction.
Testing / Validation
- Test multiple levels of error reduction within WBC regions.
- Assess impact on analysis stability — instability risk will constrain how aggressive we can be.
- Evaluate the ability to relocate currents more accurately.
- Desired outcome: reduction of persistent SST biases in energetic regions (Gulf Stream, Kuroshio, etc.).