NAME

       i.evapo.pt  - 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

AUTHORS

       Yann Chemin, GRASS Development Team, 2007-08

SOURCE CODE

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

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual