GRASS GIS manual: i.evapo.pt

NAME

i.evapo.pt - Computes evapotranspiration calculation Prestley and Taylor formulation, 1972.

KEYWORDS

imagery, evapotranspiration

SYNOPSIS

i.evapo.pt
i.evapo.pt help
i.evapo.pt [-z] netradiation=name soilheatflux=name airtemperature=name atmosphericpressure=name priestleytaylorcoef=float output=name [--overwrite] [--verbose] [--quiet]

Flags:

-z: Set negative ETa to zero
--overwrite: Allow output files to overwrite existing files
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

netradiation=name: Name of input net radiation raster map [W/m2]
soilheatflux=name: Name of input soil heat flux raster map [W/m2]
airtemperature=name: Name of input air temperature raster map [K]
atmosphericpressure=name: Name of input atmospheric pressure raster map [millibars]
priestleytaylorcoef=float: Prestley-Taylor coefficient; Default: 1.26
output=name: Name of output evapotranspiration raster map [mm/d]

DESCRIPTION

i.evapo.PT Calculates the diurnal evapotranspiration after Prestley and Taylor (1972). The Priestley-Taylor model (Priestley and Taylor, 1972) is a modification of Penman’s more theoretical equation.

NOTES

RNETD optional output from i.evapo.potrad is giving good results as input for net radiation in this module. Alpha values: 1.32 for estimates from vegetated areas as a result of the increase in surface roughness (Morton, 1983; Brutsaert and Stricker, 1979) 1.26 is applicable in humid climates (De Bruin and Keijman, 1979; Stewart and Rouse, 1976; Shuttleworth and Calder, 1979), and temperate hardwood swamps (Munro, 1979) 1.74 has been recommended for estimating potential evapotranspiration in more arid regions (ASCE, 1990). This Worked well in Greece with University of Thessaloniki. Alpha values extracted from: http://www.civil.uwaterloo.ca/Watflood/Manual/02_03_1.htm

TODO

AUTHORS

Yann Chemin, GRASS Development team, 2007-08

Last changed: $Date: 2011-01-12 07:59:43 -0800 (Wed, 12 Jan 2011) $

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