1i.evapo.time(1)               Grass User's Manual              i.evapo.time(1)
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NAME

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

11       imagery, evapotranspiration
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SYNOPSIS

14       i.evapo.time
15       i.evapo.time --help
16       i.evapo.time         eta=name[,name,...]        eta_doy=name[,name,...]
17       eto=name[,name,...]        eto_doy_min=float         start_period=float
18       end_period=float   output=name   [--overwrite]   [--help]   [--verbose]
19       [--quiet]  [--ui]
20
21   Flags:
22       --overwrite
23           Allow output files to overwrite existing files
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25       --help
26           Print usage summary
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28       --verbose
29           Verbose module output
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31       --quiet
32           Quiet module output
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34       --ui
35           Force launching GUI dialog
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37   Parameters:
38       eta=name[,name,...] [required]
39           Names of satellite ETa raster maps [mm/d or cm/d]
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41       eta_doy=name[,name,...] [required]
42           Names of satellite ETa Day of Year (DOY) raster maps [0-400] [-]
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44       eto=name[,name,...] [required]
45           Names of meteorological station ETo raster maps  [0-400]  [mm/d  or
46           cm/d]
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48       eto_doy_min=float [required]
49           Value of DOY for ETo first day
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51       start_period=float [required]
52           Value of DOY for the first day of the period studied
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54       end_period=float [required]
55           Value of DOY for the last day of the period studied
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57       output=name [required]
58           Name for output raster map
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DESCRIPTION

61       i.evapo.time  (i.evapo.time_integration) integrates ETa in time follow‐
62       ing a reference ET (typically) from a set  of  meteorological  stations
63       dataset.  Inputs:
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65           ·   ETa images
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67           ·   ETa images DOY (Day of Year)
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69           ·   ETo images
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71           ·   ETo DOYmin as a single value
72       Method:
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74       1      each ETa pixel is divided by the same day ETo and become ETrF
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76       2      each ETrF pixel is multiplied by the ETo sum for the representa‐
77              tive days
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79       3      Sum all n temporal [ETrF*ETo_sum] pixels to make a summed(ET) in
80              [DOYmin;DOYmax]
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82       representative   days  calculation:  let  assume  i  belongs  to  range
83       [DOYmin;DOYmax]
84       DOYbeforeETa[i] = ( DOYofETa[i] - DOYofETa[i-1] ) / 2
85       DOYafterETa[i] = ( DOYofETa[i+1] - DOYofETa[i] ) / 2
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NOTES

88       ETo images preparation: If you only  have  one  meteorological  station
89       data set, the easiest way is:
90       n=0
91       for ETo_val in Eto[1] Eto[2] ...
92       do
93            r.mapcalc "eto$n = $ETo_val"
94            `expr n = n + 1`
95       done
96       with  Eto[1],  Eto[2], etc being a simple copy and paste from your data
97       file of all ETo values separated by an empty space from each other.
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99       If you have several meteorological stations data, then you need to grid
100       them  by  generating Thiessen polygons or using different interpolation
101       methods for each day.
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103       For multi-year calculations,  just  continue  incrementing  DOY  values
104       above  366, it will continue working, up to maximum input of 400 satel‐
105       lite images.
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SEE ALSO

108        i.eb.eta, i.evapo.mh, i.evapo.pt, i.evapo.pm, r.sun
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AUTHOR

111       Yann Chemin, International Rice Research Institute, The Philippines
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SOURCE CODE

114       Available at: i.evapo.time source code (history)
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116       Main index | Imagery index | Topics index | Keywords index |  Graphical
117       index | Full index
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119       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual
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123GRASS 7.8.2                                                    i.evapo.time(1)
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