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PHYPRO-01_agn_OSMOSIS_science
Last edition: Wikinfo(changed_ts)? by Wikinfo(changed_by)?
The PI is responsible to closely follow the progress of the action, and especially to contact NEMO project manager if the delay on preview (or review) are longer than the 2 weeks expected.
Summary
| Action | PHYPRO-01_agn_OSMOSIS_science |
|---|---|
| PI(S) | George Nurser |
| Digest | Improvements to OSMOSIS OBL to improve behaviour in shelf-sea areas and under sea ice |
| Dependencies | If any |
| Branch | source:/NEMO/branches/{YEAR}/dev_r{REV}_{ACTION_NAME} |
| Previewer(s) | Names |
| Reviewer(s) | Names |
| Ticket | #2352 |
Description
Improve OSMOSIS ocean boundary layer (OBL) model in 3 areas:
- Ensure consistent behaviour of OSMOSIS-OBL under ice. Revert to classic shear turbulence based on ice-ocean turbulent friction velocity where ice areal coverage is high; scale with ice fraction between shear turbulence and Langmuir turbulence model. Where Stokes drift unavailable, move to parametrised form.
- Improve representation of OSMOSIS-OBL mixing in equatorial regions. Include mixing associated with shear of mean flow as in equatorial undercurrent.
- Mixing in shelf seas. The OSMOSIS-OBL is primarily a surface boundary layer model and so is not set up for bottom-driven tidal mixing. We intend to transition to GLS in shelf seas.
Implementation
The development branch for 2019-WP action VALID-02_GeorgeN-evalOSMOSIS has recently been synchronized with source:/NEMO/trunk@12925 (changesets [12928] and [12934])and will form the basis for the source-code "streamlining" activities of action 2020WP/ENHANCE-14_smueller_OSMOSIS_streamlining. A new branch with the new physics will be spun-off this streamlined branch 2020WP/ENHANCE-14_smueller_OSMOSIS_streamlining.
Changes for (1) and (2) will be mostly restricted to the routine zdfosm.F90. There will be a new subroutine added to handle the shear-induced mixing.
The transitioning to GLS will require setting up of the GLS routine zdfgls.F90 and code to link it with the master routine zdfosm in zdfosm.F90
Documentation updates
An extra paragraph or two will be added to the documentation in section 9.1.5 of the manual.
Preview
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Tests
- UNDER_ICE_OSMOSIS_TEST
Aim: to test that OSMOSIS_OBL behaves correctly under ice for a range of ice fractions
Configuration: 2D model SI3 + OCE, with domain_cfg, idealised forcing (cooling/freezing phase + warming/melting phase , initial state with gradation in ice cover.
Output diagnosed mixed-layer depth after specified time of cooling/mixing. Check against control run values.
Defined but not developed.
- EQUIATORIAL_OSMOSIS_TEST
Aim: to test that OSMOSIS_OBL gives a reasonable diurnal cycle of near-equatorial mixing
Configuration: 2D model with ideal-age tracer TOP + OCE along meridional section across the equator 5°S--5°N with initial state with westerly surface zonal flow and easterly zonal undercurrent, zero ideal-age tracer throughout.
Idealised diurnal cycle of surface forcing.
Output mixed-layer depth + vertical profile of age tracer after specified time of cooling/mixing. Check against control run values.
Defined but not developed.
- SHELF_OSMOSIS_TEST
Aim: to test that OSMOSIS_OBL gives a smooth transition between open ocean and shelf conditioins
Configuration uncertain. Might again use 2D model with gradient in tidal flow and/or bottom depth Output and check profile of diagnosed mixed-layer depth against control run values.
Loosely defined and not developed.
Review
...
