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i.evapo.time(1)		    GRASS GIS User's Manual	       i.evapo.time(1)

NAME
       i.evapo.time   -	 Computes  temporal integration	of satellite ET	actual
       (ETa) following the daily ET reference (ETo) from  meteorological  sta-
       tion(s).

KEYWORDS
       imagery,	evapotranspiration

SYNOPSIS
       i.evapo.time
       i.evapo.time --help
       i.evapo.time	    eta=name[,name,...]	       eta_doy=name[,name,...]
       eto=name[,name,...]   eto_doy_min=float	 start_period=float    end_pe-
       riod=float output=name  [--overwrite]  [--help]	[--verbose]  [--quiet]
       [--ui]

   Flags:
       --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:
       eta=name[,name,...]A [required]
	   Names of satellite ETa raster maps [mm/d or cm/d]

       eta_doy=name[,name,...]A	[required]
	   Names of satellite ETa Day of Year (DOY) raster maps	[0-400]	[-]

       eto=name[,name,...]A [required]
	   Names of meteorological station ETo raster maps  [0-400]  [mm/d  or
	   cm/d]

       eto_doy_min=floatA [required]
	   Value of DOY	for ETo	first day

       start_period=floatA [required]
	   Value of DOY	for the	first day of the period	studied

       end_period=floatA [required]
	   Value of DOY	for the	last day of the	period studied

       output=nameA [required]
	   Name	for output raster map

DESCRIPTION
       i.evapo.time  (i.evapo.time_integration)	integrates ETa in time follow-
       ing a reference ET (typically) from a set  of  meteorological  stations
       dataset.	 Inputs:

	   o   ETa images

	   o   ETa images DOY (Day of Year)

	   o   ETo images

	   o   ETo DOYmin as a single value
       Method:

       1      each ETa pixel is	divided	by the same day	ETo and	become ETrF

       2      each ETrF	pixel is multiplied by the ETo sum for the representa-
	      tive days

       3      Sum all n	temporal [ETrF*ETo_sum]	pixels to make a summed(ET) in
	      [DOYmin;DOYmax]

       representative	days  calculation:  let	 assume	 i  belongs  to	 range
       [DOYmin;DOYmax]
       DOYbeforeETa[i] = ( DOYofETa[i] - DOYofETa[i-1] ) / 2
       DOYafterETa[i] =	( DOYofETa[i+1]	- DOYofETa[i] )	/ 2

NOTES
       ETo images preparation: If you only  have  one  meteorological  station
       data set, the easiest way is:
       n=0
       for ETo_val in Eto[1] Eto[2] ...
       do
	    r.mapcalc "eto$n = $ETo_val"
	    `expr n = n	+ 1`
       done
       with  Eto[1],  Eto[2], etc being	a simple copy and paste	from your data
       file of all ETo values separated	by an empty space from each other.

       If you have several meteorological stations data, then you need to grid
       them  by	 generating Thiessen polygons or using different interpolation
       methods for each	day.

       For multi-year calculations,  just  continue  incrementing  DOY	values
       above  366, it will continue working, up	to maximum input of 400	satel-
       lite images.

SEE ALSO
	i.eb.eta, i.evapo.mh, i.evapo.pt, i.evapo.pm, r.sun

AUTHOR
       Yann Chemin, International Rice Research	Institute, The Philippines

SOURCE CODE
       Available at: i.evapo.time source code (history)

       Main index | Imagery index | Topics index | Keywords index |  Graphical
       index | Full index

       A(C) 2003-2021 GRASS Development	Team, GRASS GIS	7.8.6 Reference	Manual

GRASS 7.8.6						       i.evapo.time(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | SEE ALSO | AUTHOR | SOURCE CODE

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