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 [required]
- Name of input net radiation raster map [W/m2]
- soilheatflux=name [required]
- Name of input soil heat flux raster map [W/m2]
- airtemperature=name [required]
- Name of input air temperature raster map [K]
- atmosphericpressure=name [required]
- Name of input atmospheric pressure raster map [millibars]
- priestleytaylorcoef=float [required]
- Prestley-Taylor coefficient
- Default: 1.26
- output=name [required]
- 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
SEE ALSO
i.evapo.pm,
i.evapo.potrad,
i.eb.netrad,
i.eb.g0
AUTHORS
Yann Chemin, GRASS Development team, 2007-08
Last changed: $Date: 2011-11-08 13:24:20 -0800 (Tue, 08 Nov 2011) $
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