Note: This addon document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade your GRASS GIS installation, and read the current addon manual page.
NAME
i.eb.z0m - Computes momentum roughness length (z0m) and surface roughness for heat transport (z0h) after Bastiaanssen (2004).
KEYWORDS
imagery,
roughness length,
energy balance,
SEBAL
SYNOPSIS
i.eb.z0m
i.eb.z0m --help
i.eb.z0m [-p] input=name [coef=float] [hv_max=float] [hmr=float] output=name [z0h=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
- -p
- Use SAVI input only with equation of Pawan (2004)
- --overwrite
- Allow output files to overwrite existing files
- --help
- Print usage summary
- --verbose
- Verbose module output
- --quiet
- Quiet module output
- --ui
- Force launching GUI dialog
Parameters:
- input=name [required]
- Name of the NDVI map [-1.0;1.0], SAVI if -p flag
- coef=float
- Value of the conversion factor from z0m and z0h (Bastiaanssen (2005) used 0.1), for -f flag
- Default: 0.1
- hv_max=float
- Value of the vegetation height at max(NDVI) i.e. standard C3 crop could be 1.5m, not needed for -p flag
- Default: 1.5
- hmr=float
- Value of the micro-relief height (h.m-r.) on flat bare ground, most references point to 2cm, not need for -p flag
- Default: 0.02
- output=name [required]
- Name of the output z0m layer
- z0h=name
- Name of the output z0h layer
i.eb.z0m calculates the momentum roughness length (z0m) and
optionally the surface roughness for heat transport (z0h) as per
SEBAL requirements from Bastiaanssen (1995).
Default: calculating from a NDVI with an deterministic equation, as seen in Bastiaanssen (1995).
Flag -p : calculating from a SAVI with an empirical equation, as seen in Pawan (2004).
This is a typical input to sensible heat flux computations of any energy balance modeling.
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.
i.eb.h0
- Bastiaanssen, W.G.M., 1995. Regionalization of surface flux
densities and moisture indicators in composite terrain; a remote
sensing approach under clear skies in mediterranean climates. PhD
thesis, Wageningen Agricultural Univ., The Netherland, 271 pp.
(PDF)
- Chemin, Y., 2012.
A Distributed Benchmarking Framework for Actual ET Models,
in: Irmak, A. (Ed.), Evapotranspiration - Remote Sensing and Modeling. InTech.
(PDF)
Yann Chemin
SOURCE CODE
Available at:
i.eb.z0m source code
(history)
Latest change: Mon Jun 28 07:54:09 2021 in commit: 1cfc0af029a35a5d6c7dae5ca7204d0eb85dbc55
Note: This addon document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade your GRASS GIS installation, and read the current addon manual page.
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GRASS Development Team,
GRASS GIS 7.8.8dev Reference Manual