NWP | MPAS | WRF| Albedo calculation

Albedo

  • If you map data to the 24-category USGS data, then albedo will be given at the model start time, based on the LANDUSE.TBL. Since the initial value is dependent on the landuse type,
  • however, the Noah LSM does not use the albedo (or any other land properties) from the LANDUSE.TBL. It uses values from the VEGPARM.TBL, and albedo is computed based on vegetation fraction, and bounded by the max and min values given in the VEGPARM.TBL.
  • WRF
  • The LANDUSE.TBL was used by all land surface model (LSM) options prior to Version 3.1.
  • The VEGPARM.TBL is used by the Noah and RUC LSMs.
  • The PX LSM uses data defined in module_sf_ssib.F.
  • The model reads fields from LANDUSE.TBL first, but then may be overwritten by values in VEGPARM.TBL if there is an overlap.

LANDUSE.TBL

VEGPARM.TBL

  • https://github.com/yyr/wrf/blob/master/run/VEGPARM.TBL
  • WRF/phys/module_sf_noahdrv.F 
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    !-----SPECIFY VEGETATION RELATED CHARACTERISTICS :
    !             ALBBCK: SFC albedo (in percentage)
    !                 Z0: Roughness length (m)
    !             SHDFAC: Green vegetation fraction (in percentage)
    !  Note: The ALBEDO, Z0, and SHDFAC values read from the following table
    !          ALBEDO, amd Z0 are specified in LAND-USE TABLE; and SHDFAC is
    !          the monthly green vegetation data
    !             CMXTBL: MAX CNPY Capacity (m)
    !             NROTBL: Rooting depth (layer)
    !              RSMIN: Mimimum stomatal resistance (s m-1)
    !              RSMAX: Max. stomatal resistance (s m-1)
    !                RGL: Parameters used in radiation stress function
    !                 HS: Parameter used in vapor pressure deficit functio
    !               TOPT: Optimum transpiration air temperature. (K)
    !             CMCMAX: Maximum canopy water capacity
    !             CFACTR: Parameter used in the canopy inteception calculati
    !               SNUP: Threshold snow depth (in water equivalent m) that
    !                     implies 100% snow cover
    !                LAI: Leaf area index (dimensionless)
    !             MAXALB: Upper bound on maximum albedo over deep snow
    !
    !-----READ IN VEGETAION PROPERTIES FROM VEGPARM.TBL

Description of MIN and MAX albedo

If you take a look in the WRF/run/VEGPARM.TBL file, you will see ALBEDOMIN and ALBEDOMAX, corresponding to each landuse type.

  • The Noah LSM scheme reads this file, then calculates albedo based on the vegetation cover fraction, and the max/min albedo. For more details, you can see the file WRF/phys/module_sf_noahlsm.F.

usemonalb (monthly albedo)

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sst_update                          = 0        ! time-varying sea-surface temp (0=no, 1=yes). If selected real 
                                                 puts SST, XICE, ALBEDO and VEGFRA in wrflowinp_d01 file, and wrf updates 
                                                 these from it at same interval as boundary file. Also requires
                                                 namelists in &time_control: auxinput4_interval, auxinput4_end_h,
                                                 auxinput4_inname = "wrflowinp_d<domain>", and io_form_auxinput4
usemonalb                           = .false.  ! use monthly albedo map instead of table value
                                                 (recommended for sst_update=1)
rdmaxalb                            = .true.   ! use snow albedo from geogrid; false means using values from table
rdlai2d                             = .false.  ! use LAI from input; false means using values from table
                                                 if sst_update=1, LAI will also be in wrflowinp file

More,

  • Modify landuse and GREENFRAC | Aug 25, 2020
    • As GREENFRAC is a 12-monthly field from geogrid, during the real.exe process, it will be interpolated to the model start time, and stored in the array "vegfra." It will also be included in wrflowinp_d* since you are using sst_update. As for modifying other variables, I guess it depends whether you think those particular variables will be affected in the area of your modifications.
    • ALBEDO12M isn't even actually used during real/wrf unless you set usemonalb= .true. in the namelist (it will be interpolated to "albbck" during real).
  • monthly albedo | Feb 19, 2024
    • You are right that albedo over the ocean is not updated even if sst_update =1.
  • WRF中修改反照率
    • wrf本身的 albedo是根据 Vtable定的，所以是不停变化的。首先要将albedo改为月的 albedo，方法是在 namelist.input 中的 &physics 中加入 usemonalb = .true.命令，然后就是利用ncl修改即可。在模式中单纯修改反照率，如果面积过大，就会造成地面平衡破坏太严重，模式易于崩溃。
  • 如何在WRF中使用2020年（最新）土地利用类型数据集？
    • WRF中土地利用类型最高分辨率是30s，且主要分为MODIS和USGS两种，其中MODIS数据是从2000年（有的也说是2001年）的MODIS卫星遥感数据，按照IGBP20分类标准得到的，总共有21类（含第21类—Lake）,USGS数据则是1992~1993年的，总共分为24类，具体类型可以参考userguide，这些数据时间都比较久远了，如果进行最新模拟的话相差20年了，所以进行了替换。

Literature Review

WRFDA, CRTM

WRFDA observation operator H uses a radiative transfer model (e.g., CRTM or RTTOV) to compute brightness temperatures from model profiles of temperature, humidity, and surface properties like surface emissivity.

The CRTM surface model includes surface emissivity/reflectivity for various surface types, including snow, ice, land, and water/ocean.

MPAS

Noah LSM

The Noah LSM does not use the albedo (or any other land properties) from the LANDUSE.TBL. It uses values from the VEGPARM.TBL, and albedo is computed based on vegetation fraction, and bounded by the max and min values given in the VEGPARM.TBL.

for climatologically varying surface albedo

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<nml_option name="config_sfc_albedo" type="logical" default_value="true" in_defaults="false"
        units="-"
        description="logical for configuration of surface albedo"
        possible_values=".true. for climatologically varying surface albedo; .false. for fixed input data"/>

<nml_option name="config_sfc_snowalbedo" type="logical" default_value="true" in_defaults="false"
        units="-"
        description="logical for configuration of maximum surface albedo for snow"
        possible_values=".true. for geographical distribution; .false. for fixed input data"/>

For climatologically varying surface albedo

NWP
#NWP #WRF #MPAS #Meteorology #Albedo #static.nc #geogrid.exe #LANDUSE
NWP | MPAS | WRF| Albedo calculation
https://waipangsze.github.io/2025/05/09/NWP-MPAS-WRF-Albedo-calculation/
Author
wpsze
Posted on
May 9, 2025
Updated on
May 9, 2025
Licensed under