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An improvement of the NSST model and the scheme to get sea surface temperature for heat fluxes claculation in UFS #891

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XuLi-NOAA opened this issue Nov 27, 2024 · 0 comments
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enhancement New feature or request

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XuLi-NOAA commented Nov 27, 2024

Description

Problem 1: In the current UFS NSST diurnal warming model, the vertical warming structure is assumed linear from surface to the base of the warm layer. This can be repalced by an exponential profile, which is more realistic based on the observations.
Problem 2: In the current UFS, there is a scheme, refered to Scheme-A.1, to derive the foundation temperature with MOM6 SST and NSST model, and then sea surface temperature for the atmosphere-ocean heat fluxes calculation. It is known this derived foundation has slightly too large diurnal variability, which can be mitigated by introducing more oceanic model layer's temperature in Scheme-A.1, in which, only the MOM6 top layer temperature is used.

Solution

Solution 1: In the current NSST Diurnal Thermocline Layer(DTL) model, DTL-1p, whose thermal control variable is the integral of the diurnal warming amount from surface (z=0) to the DTL base (z=zw), the actual diurnal warming amount at a certain depth is then distributed by assuming a linear vertical structure. In this project, based on the integral, can be regarded as a diurnal warming heat content of DTL, the distribution of the warming amount will be determined with a simulated exponential vertical structure.
Solution 2: In MOM6, the SST is defined as the average from z=0 to a namelist variable, HMIX_SFC_PROP, which is 1 meter at present by default. This means basically only MOM6 top layer temperature is used in Scheme-A.1. In this project, HMIX_SFC_PROP will set to be 20 to derive a better foundation temperature.

Alternatives

Ideally, increasing the vertical resolution of the oceanic model is the solution to adress the oceanic diurnal warming effect. That is the next step.

Testing:

  1. Have you tested the code changes? On what platforms?
  2. Have you run regression test in ufs-weather-model or ufs-s2s-model with code changes?
  • Will the baseline results change?
  • If yes, please give brief explanation of your code updates on the regression test.

Dependent PRs:

Directly reference any issues or PRs in this or other repositories that this is related to, and describe how they are related. Example:

  • required to support noaa-emc/GFDL_atmos_cubed_sphere/issues/<issue_number>
  • ncar/ccpp-physics/pull/<pr_number>
  • associated ufs-weather-model/pull/<pr_number>
@XuLi-NOAA XuLi-NOAA added the enhancement New feature or request label Nov 27, 2024
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