opposite sign of ground heat flux in urban models with Noah-MP land surface model #1921
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@cenlinhe Would you like to comment on this post? |
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Yes, this is very likely a bug. I will look into more detail and try to fix it in the next 1~2 weeks. |
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I confirm that this is a bug: NCAR/hrldas#114 (comment) |
weiwangncar
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Jan 13, 2024
TYPE: bug fix KEYWORDS: Noah-MP, snow combine, vegetation fraction scaling, urban ground heat flux SOURCE: Cenlin He (NCAR/RAL) DESCRIPTION OF CHANGES: There are a few bug fixes for Noah-MP related processes: (1) the snow layer index in snow COMBINE module was wrong, causing model crash when snow layer changes by more than 1 layer within one timestep; This has been fixed by using the correct layer index. (2) the ground heat flux sign in Noah-MP column model (positive: downward) is inconsistent with that in urban canopy model (positive: upward), leading to wrong diagnostic grid-mean ground heat flux calculation for urban grid. This only affects the diagnostic value for output. See this issue: #1921 and NCAR/hrldas#114 (3) there is a bug in vegetation fraction (FVEG) scaling for stomata resistance calculation (NCAR/noahmp#92) and canopy interception calculation (NCAR/noahmp#91). LIST OF MODIFIED FILES: list of changed files (use `git diff --name-status master` to get formatted list): phys/noahmp/src/module_sf_noahmplsm.F phys/noahmp/src/module_sf_noahmpdrv.F TESTS CONDUCTED: 1. Tested successfully in NCAR Cheyenne HPC for 13-km run over the entire CONUS region 2. The Jenkins tests are all passing. RELEASE NOTE: Noah-MP bug fix for snow combination, vegetation fraction scaling, and urban ground heat flux sign.
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NCAR/hrldas#114 (comment)
The ground heat flux in Noah-MP is downwards positive from surface, but it is downwards negative from surface in Noah land surface model (LSM).
To keep the same direction of ground heat flux between urban models (SLUCM, BEP, or BEM) and the land surface model (Noah or Noah-MP) is required to calculate surface energy balance at the grid mean level.
In Noah LSM, the ground heat flux direction is the same as urban models, but differ in Noah-MP.
To make the same direction using SLUCM with Noah-MP LSM at the grid mean level.
https://github.com/NCAR/noahmp/blob/981d4f859ce6c64213d38a783654c05b47b3485e/drivers/wrf/module_sf_noahmpdrv.F#L3508
revise to
GRDFLX(I,J) = FRC_URB2D(I,J) * (-1.0 * G_URB) + (1-FRC_URB2D(I,J)) * GRDFLX(I,J) ![W/m/m]
and for BEP, BEM
https://github.com/NCAR/noahmp/blob/981d4f859ce6c64213d38a783654c05b47b3485e/drivers/wrf/module_sf_noahmpdrv.F#L3737
revise to
grdflx(i,j) = (1.-frc_urb2d(i,j)) * grdflx_rural(i,j)+ frc_urb2d(i,j) * grdflx_urb(i,j) * -1.0
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