monthly albedo

[francescomaicu]

Dear Supporters,
in this thread I read that the usemonalb option (real/wrf) should also write the used values to the ALBBCK variable.
Well, I changed in my domain files the monthly values of the ALBEDO12M variable over the ocean according to other seasonal values that we are more familiar with, in the Mediterannean Sea.
They are correctly displayed in the domain file, but I don't see any change when I run real to generate the WRF input files.
Both in the wrflowinp_01 and wrfinput_01 the ALBBCK on the ocean is not changed (still 0.08), elsewhere is changed accordingly with the prescribed monthly values in the domain file. BTW, sst_update = 1 in my real namelist.
Looks like the update of the albedo is not effective over the ocean, or alm I missing something?
P.S. ALBEDO still unchanged in the WRF outputs (sst_update here is set to false because the model is coupled with NEMO)
Thank you very much

 

[Ming Chen]

You are right that albedo over the ocean is not updated even if sst_update =1.

 

[francescomaicu]

Dear @Ming Chen
I commented line 1286 in dyn_em/module_initialize_real.F (WRF4.2)

               IF ( grid%landmask(i,j) .LT. 0.5 ) THEN
               !   grid%albbck(i,j) = 0.08
                  grid%snoalb(i,j) = 0.08
               END IF

and commented line 1128 in phys/module_physics_init.F

     IF(XLAND(i,j) .LT. 1.5)THEN
        .
        .
        .
    ELSE
!       IF(mminlu_loc .EQ. '    ') ALBBCK(i,j)=0.08
       ALBEDO(i,j)=ALBBCK(i,j)
        .
        .
        .         
     ENDIF

I am not sure the second change is needed, but at the end now I have time-interpolated monthly values of albedo on the ocean.

 

[Ming Chen]

That is great ! Thank you for the update !

 

[lff]

Hello, all!,

I am new to WRF and am currently trying to perform two experiments by replacing the surface albedo. The first set is a control run without changing albedo, and the second set modifies the albedo for a specific land surface category.

I have conducted a 10-day simulation and found that in the wrfout output files, the albedo differs between the two experiments only at the first time step, while from the second time step onwards, the albedo values are almost identical between the two runs.

My procedure for replacing albedo is as follows:

• I modified the ALBEDO12M variable inside the geo_em.d01.nc file.
• Then I ran metgrid.exe.
• In the namelist.input, I set usemonalb = true.
• Finally, I ran real.exe and wrf.exe to perform the simulations.

Below is the relevant part of the &physics section in my namelist.input:

&physics
sf_surface_physics = 4, ! Noah-MP
num_soil_layers = 4,
bl_pbl_physics = 1,
sf_sfclay_physics = 1,
ra_lw_physics = 4,
ra_sw_physics = 4,
cu_physics = 1,
mp_physics = 8,
radt = 25,
bldt = 0,
cudt = 5,
num_land_cat = 21,
sf_urban_physics = 0,
usemonalb = true,
/

&noah_mp
dveg = 2, !On LAI predicted; FVEG calculated
/

My questions are:

1. Is this approach of replacing albedo by modifying ALBEDO12M in geo_em.d01.nc and setting usemonalb = true correct?
2. Why does the albedo difference between the two experiments only appear at the first time step in the output?
3. For consistency, should I set usemonalb = true in both the control and modified experiments?

Thank you very much for your time and help!

 

[Ming Chen]

Can you create a new thread? Thanks.

 

[lff]

Can you create a new thread? Thanks.

I have created a new thread, please see replacement of monthly albedo
Thanks for your time and help!