What's the meaning of GRDFLX value in water body?

[dengxw]

Hi all,
I am choosing the Unified Noah land-surface model in WRFv3.9.1, and have run a case.
sf_surface_physics = 2, 2, 2, （ my choice）

GRDFLX is the heat flux that goes into the ground.
But I noticed that in water body(LU_INDEX=17 in IGBP-Modified MODIS 20-category Land Use Categories), GRDFLX also are valid values.
I ’m wondering the meaning of GRDFLX value in water body.
Is the heat flux that goes into the water? Or the heat flux that goes into the underwater soil?
I look forward to hearing from you！

Thank you!

 

[Yuanlin]

Hi dengxw,

I may have the same problem. I also used Unified Noah land-surface model for simulation, and the results show that GRDFLX of once frozen lake grids will always have a constant value when it back to water body (the GRDFLX of not frozen water grids are zero). By the way, when the lake grids frozen, Noah scheme will set it to land point, which may have something to do with this problem.

I used sst_update=1, the HFX and LH seems reasonable. But I not sure if this problem affects other variables.

I really hope to get a reply from WRF team.

Thanks!

Yuanlin

 

[Ming Chen]

Hi Yuanlin and Dengxw,

I believe that GRDFLX has no physical meaning over non-frozen water point. This is because WRF doesn't calculate surface energy budget and predict TSK over non-frozen water points. Once the water is frozen, the previous water point will be reset to ice and treated as a and point. In this case, surface energy budget will be calculated and GRDFLX is the heat flux that goes down to ice layer.

 

[Yuanlin]

Got it, thank you very much!

 

[cibaouc]

Hi Yuanlin and Dengxw,

I believe that GRDFLX has no physical meaning over non-frozen water point. This is because WRF doesn't calculate surface energy budget and predict TSK over non-frozen water points. Once the water is frozen, the previous water point will be reset to ice and treated as a and point. In this case, surface energy budget will be calculated and GRDFLX is the heat flux that goes down to ice layer.

is GRDFLX positive downward ?

 

[Ming Chen]

it is negative if downward from surface