UCM output albedo is weird

[QiSun]

Hi WRF experts,

when I use WRFv4.3.3 and using single layer model, the albedo in urban region looks like this, is this pattern and value reasonable or something wrong here? Because from the URBAN.TBL the value is around 0.2, here has some time changes.
Another question is in the VEG.TBL the albedo for cropland is around 0.17-0.23, and for urban is around 0.15, seems like the albedo in URBAN.TBL is quite high for urban region.

Looking forward to your response!
Cheers

 

[Ming Chen]

What land surface model did you use to run this case?

I will discuss with our expert regarding the albedo issue in URBAN.TBL. I will get back to you later.

 

[Ming Chen]

Please upload your namelist.input for me to take a look. Thanks.

 

[QiSun]

I use NOAH， and the attachment is the settings in WPS and WRF, thanks a lot for your reply!!!

 

[QiSun]

Please upload your namelist.input for me to take a look. Thanks.

thanks again, looking forward to your response!

 

[Ming Chen]

Thank you for uploading the files.

The albedo value is reasonable based on our expert's opinion. The grid-level albedo is computed as:

ALBEDO(I,J) = FRC_URB2D(I,J)*ALB_URB+(1-FRC_URB2D(I,J))*ALBEDOK

The time variation of the grid-level albedo is attributed to the fact that urban albedo (ALB_URB) varies with time, since the sky view factor for buildings and roads change with solar zenith angle. Note that although albedo is prescribed to be 0.2 for wall, road, and roof surfaces, the 'true' value of albedo is recalculated as described above.

Hope this is helpful. Please let us know if you still have questions.

 

[Tony]

Thank you for uploading the files.

The albedo value is reasonable based on our expert's opinion. The grid-level albedo is computed as:

ALBEDO(I,J) = FRC_URB2D(I,J)*ALB_URB+(1-FRC_URB2D(I,J))*ALBEDOK

The time variation of the grid-level albedo is attributed to the fact that urban albedo (ALB_URB) varies with time, since the sky view factor for buildings and roads change with solar zenith angle. Note that although albedo is prescribed to be 0.2 for wall, road, and roof surfaces, the 'true' value of albedo is recalculated as described above.

Hope this is helpful. Please let us know if you still have questions.

Hi Ming chen,

Could you please kindly provide some information about how the valuable (ALB_URB and ALBEDOK) is calculated in WRF?

Thanks a lot,

Best
Tony

 

[Ming Chen]

Tony,

ALBEDOK is specified to 0.2 over urban points (see module_sf_noahdrv.F).
ALB_URB is calculated in the codes "module_sf_urban.F", where you can find details how it is calculated.

Please also refer to the papers below:

Chen, F., H. Kusaka, R. Bornstain, J. Ching, C.S.B. Grimmond, S. Grossman-Clarke, T. Loridan, K. Manning, A. Martilli, S. Miao, D. Sailor, F. Salamanca, H. Taha, M. Tewari, X. Wang, A. Wyszogrodzki, and C. Zhang, 2011: The integrated WRF/urban modeling system: development, evaluation, and applications to urban environmental problems. International Journal of Climatology, 31, 273-288. DOI: 10.1002/joc.2158.

Martilli A, Clappier A, and Rotach M.W., 2002: An urban surface exchange parameterization for mesoscale models. Bound.-Layer Meteorol., 104, 261–304.