Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current 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: Monday Jan 30 19:52:26 2023 in commit: cac8d9d848299297977d1315b7e90cc3f7698730
Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.
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GRASS Development Team,
GRASS GIS 8.2.2dev Reference Manual