i.eb.z0m0 - GRASS GIS manual

NAME

i.eb.z0m0 - Computes momentum roughness length (z0m) and surface roughness for heat transport (z0h) after Bastiaanssen (2004).

KEYWORDS

imagery, energy balance, SEBAL, SEBS, roughness length

SYNOPSIS

i.eb.z0m0

i.eb.z0m0 --help

i.eb.z0m0 [-h] ndvi=name [coef=float] hv_max=float hmr=float output=name [z0h=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-h: z0h output (You have to input a coef value)
--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:

ndvi=name [required]: Name of the NDVI map [-1.0;1.0]
coef=float: Value of the converion factor from z0m and z0h (Bastiaanssen (2005) used 0.1); Default: 0.1
hv_max=float [required]: Value of the vegetation height at max(NDVI) i.e. standard C3 crop could be 1.5m; Default: 1.5
hmr=float [required]: Value of the micro-relief height (h.m-r.) on flat bare ground, most references point to 2cm; Default: 0.02
output=name [required]: Name of the output z0m layer
z0h=name: Name of the output z0h layer

DESCRIPTION
NOTES
TODO
SEE ALSO
AUTHOR

DESCRIPTION

i.eb.z0m0 calculates the momentum roughness length (z0m) and optionally the surface roughness for heat transport (z0h) as per SEBAL requirements from bastiaanssen (1995). This version is calculating from a NDVI with an deterministic equation, as seen in Bastiaanssen (1995). 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. There, fixed.