QX in Latent Heat Flux Calculation

[ejanzon]

Hi,

I am trying to reproduce the total LH calculation from SFCLAY using the WRF model output. I modified the EM_COMMON registry to have the coefficient FLQC and QSFC in the model output and now I am having trouble understanding the meaning of the variable QX. If I understand it (my FORTRAN understanding is not good, so please bear with me), the
phys/module_sf_sfclay.F code uses the 3D atmospheric mixing ratio (QV3D), separates this into single columns (QV1D), and then uses this to calculate a QX. When I try to calculate the moisture gradient using QSFC-QVAPOR over a grid cell, I get values that an order of magnitude greater than I would expect, so I think I am interpreting this the wrong way. I am also a bit confused about the height of QX above ground level. Is this the same as the first model level or the half-model level above the first model level?

So my questions are:
1) Is QVAPOR from the standard model output equivalent to QV3D?

2) Is QX taken directly at the first model level or the first half-model level above the LSM?

 

[Ming Chen]

Please see my answers below:

Hi,

I am trying to reproduce the total LH calculation from SFCLAY using the WRF model output. I modified the EM_COMMON registry to have the coefficient FLQC and QSFC in the model output and now I am having trouble understanding the meaning of the variable QX. If I understand it (my FORTRAN understanding is not good, so please bear with me), the
phys/module_sf_sfclay.F code uses the 3D atmospheric mixing ratio (QV3D), separates this into single columns (QV1D), and then uses this to calculate a QX. When I try to calculate the moisture gradient using QSFC-QVAPOR over a grid cell, I get values that an order of magnitude greater than I would expect, so I think I am interpreting this the wrong way. I am also a bit confused about the height of QX above ground level. Is this the same as the first model level or the half-model level above the first model level?

So my questions are:
1) Is QVAPOR from the standard model output equivalent to QV3D?

yes it is

2) Is QX taken directly at the first model level or the first half-model level above the LSM?

QX is qvapor at the first half-model level.

 

[ejanzon]

Okay, this makes sense. Thank you Ming Chen.