rad_trncf (nhru)

PRMS Parameter Name(s): rad_trncf

BAGIS-P Model Toolbox: bagis_p_vegetation_methods.tbx

BAGIS-P Model Name: Rad_Trncf

Required DATABIN Layer(s):

• db_cover_type: Landfire_EVT

• db_cover_density: NLCD_TreeCover

Parameter Description: Transmission coefficient for short-wave radiation through winter plant canopy. This parameter is currently computed from a mathematical formula created using an average curve George Leavesley developed from 2 curves reported in the literature. There are probably more current relations reported in the literature but in most cases they are a function of the cover density of the dominant vegetation canopy. The current equation is

rad_trncf = a * e(-b * x)

where a= 0.9917, b= 2.7557, and x is the vegetation winter cover density (covden_win). rad_trncf varies by vegetation type but there are limited data available for varying this computation.

Methods:

• 1. Reclassify “db_cover_type” raster based on “COV_TYPE” value to create winter_weights raster (Bare Ground: 0 → 0; Grass: 1 → 80; Shrub: 2 → 70; Deciduous Trees: 3 → 60; Coniferous Trees: 4 → 100)

  2. Using Raster Calculator, multiply db_tree_cover_density and winter_weights, then divide the output by 10000 (to convert % to decimal) to create cov_dens_summer_weighted raster.

  3. Calculate the MEAN of cov_dens_summer_weighted for each HRU using Zonal Statistics as Table.

  4. Copy the MEAN output value as the parameter value under the new field, “fld_rad_trncf”.

  5. Use Calculate Field to apply Rad_Tmcf calculation with the following expression:

0.9917 * (2.718281828459 ^ (-2.7557 * [fld_rad_trncf]))

6. Update final Rad_Trncf table.

BAGIS-P GUI Example: