i.eb.z0m0

Computes momentum roughness length (z0m) and surface roughness for heat transport (z0h) after Bastiaanssen (2004).

i.eb.z0m0 [-h] ndvi=name [coef=float] hv_max=float hmr=float output=name [z0h=name] [--overwrite] [--verbose] [--quiet] [--qq] [--ui]

Example:

i.eb.z0m0 ndvi=name hv_max=1.5 hmr=0.02 output=name

grass.script.run_command("i.eb.z0m0", ndvi, coef=0.1, hv_max=1.5, hmr=0.02, output, z0h=None, flags=None, overwrite=False, verbose=False, quiet=False, superquiet=False)

Example:

gs.run_command("i.eb.z0m0", ndvi="name", hv_max=1.5, hmr=0.02, output="name")

Parameters

Command linePython (grass.script)

ndvi=name [required]
    Name of the NDVI map [-1.0;1.0]
coef=float
    Value of the converion factor from z0m and z0h (Bastiaanssen (2005) used 0.1)
    Default: 0.1
hv_max=float [required]
    Value of the vegetation height at max(NDVI) i.e. standard C3 crop could be 1.5m
    Default: 1.5
hmr=float [required]
    Value of the micro-relief height (h.m-r.) on flat bare ground, most references point to 2cm
    Default: 0.02
output=name [required]
    Name of the output z0m layer
z0h=name
    Name of the output z0h layer
-h
    z0h output (You have to input a coef value)
--overwrite
    Allow output files to overwrite existing files
--help
    Print usage summary
--verbose
    Verbose module output
--quiet
    Quiet module output
--qq
    Very quiet module output
--ui
    Force launching GUI dialog

ndvi : str, required
    Name of the NDVI map [-1.0;1.0]
    Used as: input, raster, name
coef : float, optional
    Value of the converion factor from z0m and z0h (Bastiaanssen (2005) used 0.1)
    Used as: 0.1
    Default: 0.1
hv_max : float, required
    Value of the vegetation height at max(NDVI) i.e. standard C3 crop could be 1.5m
    Used as: 0.1
    Default: 1.5
hmr : float, required
    Value of the micro-relief height (h.m-r.) on flat bare ground, most references point to 2cm
    Used as: 0.1
    Default: 0.02
output : str, required
    Name of the output z0m layer
    Used as: output, raster, name
z0h : str, optional
    Name of the output z0h layer
    Used as: output, raster, name
flags : str, optional
    Allowed values: h
    h
        z0h output (You have to input a coef value)
overwrite: bool, optional
    Allow output files to overwrite existing files
    Default: False
verbose: bool, optional
    Verbose module output
    Default: False
quiet: bool, optional
    Quiet module output
    Default: False
superquiet: bool, optional
    Very quiet module output
    Default: False

DESCRIPTION

i.eb.z0m0 calculates the momentum roughness length (z0m) and optionally the surface roughness for heat transport (z0h) as per SEBAL requirements from bastiaanssen (1995). This version is calculating from a NDVI with an deterministic equation, as seen in Bastiaanssen (1995). This is a typical input to sensible heat flux computations of any energy balance modeling.

NOTES

The NDVI map input and the ndvi_max operation set, is only to get a linear relationship from NDVI to vegetation height. The latter being related to z0m by a factor 7. If you happen to have a vegetation height (hv) map, then z0m=hv/7 and z0h=0.1*z0m. There, fixed.

TODO

AUTHOR

Yann Chemin, International Rice Research Institute, The Philippines

SOURCE CODE

Available at: i.eb.z0m0 source code (history)
Latest change: Thursday Feb 20 13:02:26 2025 in commit 53de819