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,
DOI: 10.5772/23571)
Yann Chemin
SOURCE CODE
Available at:
i.eb.z0m source code
(history)
Latest change: Monday Nov 11 18:04:48 2024 in commit: 59e289fdb093de6dd98d5827973e41128196887d
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GRASS GIS 8.4.1dev Reference Manual