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wet canopy fraction is incorrectly a function of vegetation fraction #91

Open barlage opened 1 year ago

barlage commented 1 year ago

The partitioning of precipitation in precip_heat/CanopyWaterIntercept is scaled by fveg/VegFrac early in the module, but maxliq/CanopyLiqWaterMax (and similar for snow) are not scaled by fveg/VegFrac. This causes a dependence of fwet/CanopyWetFrac on vegetation fraction. I see two possible solutions:

  1. the easy one is to scale capacity by vegetation fraction (I have tested this and it does solve the issue)
  2. multiply by vegetation fraction later when water is input to the soil

I like solution 2 better since it is clearer to understand and the canopy water would be a physical value that is actually on the leaf and not spread across the grid.

cenlinhe commented 1 year ago

I have fixed this issue using the easy quick solution in this commit in release-v4.5-WRF branch: https://github.com/NCAR/noahmp/commit/0fd17e50a3cbdb4ddd6ba00196927803f656fed0 The fix in v5.0 (included in release-v5.0.1) is in this commit: https://github.com/NCAR/noahmp/commit/a7dd399972fca4d477c43654d384287ad62114a2