i.evapo.pt.1grass - Man Page
Computes evapotranspiration calculation Priestley and Taylor formulation, 1972.
Keywords
imagery, evapotranspiration
Synopsis
i.evapo.pt
i.evapo.pt --help
i.evapo.pt [-z] net_radiation=name soil_heatflux=name air_temperature=name atmospheric_pressure=name priestley_taylor_coeff=float output=name [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags
- -z
Set negative ETa to zero
- --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
- net_radiation=name [required]
Name of input net radiation raster map [W/m2]
- soil_heatflux=name [required]
Name of input soil heat flux raster map [W/m2]
- air_temperature=name [required]
Name of input air temperature raster map [K]
- atmospheric_pressure=name [required]
Name of input atmospheric pressure raster map [millibars]
- priestley_taylor_coeff=float [required]
Priestley-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: Watflood manual.
See Also
i.evapo.mh, i.evapo.pm, i.evapo.time, i.eb.netrad, r.sun
Author
Yann Chemin, GRASS Development Team, 2007-08
Source Code
Available at: i.evapo.pt source code (history)
Accessed: Saturday Nov 09 07:56:13 2024
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