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, SEBALSYNOPSIS
i.eb.z0m
i.eb.z0m --helpi.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
Table of contents
DESCRIPTION
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.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.TODO
SEE ALSO
i.eb.h0REFERENCES
- 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)
AUTHOR
Yann CheminSOURCE 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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