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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

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.h0

REFERENCES

AUTHOR

Yann Chemin

Last changed: $Date: 2015-01-25 14:46:47 +0100 (Sun, 25 Jan 2015) $

SOURCE CODE

Available at: i.eb.z0m source code (history)


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