GVF & GREENFRAC

[Miao_Yang]

Dear all:

Many papers emphasize that the green vegetation fraction (GVF) is one of the key parameter in the Noah LSM (Ref.1).
However, I cannot find this indicator in WRF.
Is GVF the GREENFRAC in GEOGRID.TBL.ARW?

Thanks in advance,
Kind regards,

 

[Ming Chen]

You are right that GVF is GREENFRAC derived from static input data.

 

[Miao_Yang]

Thank you very much for your reply!

I would like to confirm that the VEGFRA parameter in the wrfinput file is the GVF mentioned in the paper, which is completely obtained from the GREENFRAC parameter in the geo_em file. Their relationship is as follows:
VEGFRA = GREENFRAC × 100
Is the above content correct?

Also, since I only need to calculate data for one week.
So after selecting the Noah land surface model, just set rdlai2d = .true., can wrf use LAI and GREENFRAC from the staticinput data instead of the table in subsequent calculations?

 

[Ming Chen]

Please see my answers below:

Thank you very much for your reply!

I would like to confirm that the VEGFRA parameter in the wrfinput file is the GVF mentioned in the paper, which is completely obtained from the GREENFRAC parameter in the geo_em file. Their relationship is as follows:
VEGFRA = GREENFRAC × 100
Is the above content correct?

This is correct.

Also, since I only need to calculate data for one week.
So after selecting the Noah land surface model, just set rdlai2d = .true., can wrf use LAI and GREENFRAC from the staticinput data instead of the table in subsequent calculations?

If rdlai2d = .true., then albedo used in Noah will be the data read from the static input data. However, this option doesn't affect GREENFRAC.

View attachment 17362
View attachment 17363

 

[Miao_Yang]

Thank you very much for your reply!

Continuing from the previous question, I would like to ask how to use VEGFRA from static geographical data instead of from a table in the Noah land surface equation if SST is not turned on?

 

[Ming Chen]

VEGFRA is actually used to calculate SHDFAC in Noah LSM. Please take a look at the code phys/module_sf_noahdrv.F, in which you can find the line:

SHDFAC=VEGFRA(I,J)/100.

Here VEGFRA is greenfrac from static input data.