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=None, verbose=None, quiet=None, superquiet=None)
Example:
gs.run_command("i.eb.z0m0", ndvi="name", hv_max=1.5, hmr=0.02, output="name")
grass.tools.Tools.i_eb_z0m0(ndvi, coef=0.1, hv_max=1.5, hmr=0.02, output, z0h=None, flags=None, overwrite=None, verbose=None, quiet=None, superquiet=None)
Example:
tools = Tools()
tools.i_eb_z0m0(ndvi="name", hv_max=1.5, hmr=0.02, output="name")
This grass.tools API is experimental in version 8.5 and expected to be stable in version 8.6.
Parameters
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: grassmods
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: grassmods
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: grassmods
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: None
verbose : bool, optional
Verbose module output
Default: None
quiet : bool, optional
Quiet module output
Default: None
superquiet : bool, optional
Very quiet module output
Default: None
ndvi : str | np.ndarray, 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: grassmods
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: grassmods
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: grassmods
Default: 0.02
output : str | type(np.ndarray) | type(np.array) | type(gs.array.array), required
Name of the output z0m layer
Used as: output, raster, name
z0h : str | type(np.ndarray) | type(np.array) | type(gs.array.array), 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: None
verbose : bool, optional
Verbose module output
Default: None
quiet : bool, optional
Quiet module output
Default: None
superquiet : bool, optional
Very quiet module output
Default: None
Returns:
result : grass.tools.support.ToolResult | np.ndarray | tuple[np.ndarray] | None
If the tool produces text as standard output, a ToolResult object will be returned. Otherwise, None
will be returned. If an array type (e.g., np.ndarray) is used for one of the raster outputs, the result will be an array and will have the shape corresponding to the computational region. If an array type is used for more than one raster output, the result will be a tuple of arrays.
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
SEE ALSO
i.eb.h0, i.eb.h_SEBAL95, i.eb.h_iter, i.eb.z0m
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