i.evapo.potrad - GRASS GIS manual

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.evapo.potrad - Potential evapotranspiration, radiative method after Bastiaanssen (1995)

KEYWORDS

Potential ET, evapotranspiration

SYNOPSIS

i.evapo.potrad

i.evapo.potrad --help

i.evapo.potrad [-rdb] albedo=name temperature=name latitude=name dayofyear=name transmissivitysingleway=name waterdensity=float [slope=name] [aspect=name] [atmosphericemissivity=float] [airtemperature=name] [surfaceemissivity=name] output=name [rnetd=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-r: Output Diurnal Net Radiation (for i.eb.eta)
-d: Slope/Aspect correction
-b: Net Radiation Bandara (1998), generic Longwave calculation, need apparent atmospheric emissivity, Air temperature and surface emissivity inputs
--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:

albedo=name [required]: Name of the Albedo layer [0.0-1.0]
temperature=name [required]: Name of the temperature layer [Degree Kelvin]
latitude=name [required]: Name of the degree latitude layer [dd.ddd]
dayofyear=name [required]: Name of the Day of Year layer [0.0-366.0]
transmissivitysingleway=name [required]: Name of the single-way transmissivity layer [0.05-1.0], defaults to 1.0 if no input file
waterdensity=float [required]: Value of the density of fresh water ~[1000-1020]; Default: 1005.0
slope=name: Name of the Slope layer ~[0-90]
aspect=name: Name of the Aspect layer ~[0-360]
atmosphericemissivity=float: Value of the apparent atmospheric emissivity (Bandara, 1998 used 0.845 for Sri Lanka); Default: 0.845
airtemperature=name: Name of the Air Temperature layer [Kelvin], use with -b
surfaceemissivity=name: Name of the Surface Emissivity layer [-], use with -b
output=name [required]: OUTPUT: Name of the Potential ET layer
rnetd=name: OUTPUT: Name of the Diurnal Net Radiation layer

DESCRIPTION
NOTES
TODO
SEE ALSO
REFERENCES
AUTHOR

DESCRIPTION

i.evapo.potrad calculates the diurnal potential evapotranspiration after Bastiaanssen (1995). This is converting all Net radiation from the diurnal period into ET. It takes input maps of Albedo, surface skin temperature, latitude, day of year, single-way transmissivity and takes input value of the density of fresh water. The "-r" flag permits output map of Diurnal net radiation to use in r.eb.eta. The "-b" flag permits a generic longwave balance calculation from surface emissivity, Air Temperature and a value of apparent atmospheric emissivity. The "-d" flag is a slope/aspect correction, not really tested, reports and tests are most welcome.

NOTES

TODO

Slope/aspect correction to be screened and tested by somebody in the known.

REFERENCES

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 Chemin, International Rice Research Institute, The Philippines

SOURCE CODE

Available at: i.evapo.potrad source code (history)

Latest change: Monday Jan 30 19:52:26 2023 in commit: cac8d9d848299297977d1315b7e90cc3f7698730