NAME

       i.eb.netrad  - Net radiation approximation (Bastiaanssen, 1995).

KEYWORDS

       imagery, energy balance, net radiation, SEBAL

SYNOPSIS

       i.eb.netrad
       i.eb.netrad --help
       i.eb.netrad       albedo=name       ndvi=name      temperature=name      localutctime=name
       temperaturedifference2m=name emissivity=name transmissivity_singleway=name  dayofyear=name
       sunzenithangle=name 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:
       albedo=name [required]
           Name of albedo raster map [0.0;1.0]

       ndvi=name [required]
           Name of NDVI raster map [-1.0;+1.0]

       temperature=name [required]
           Name of surface temperature raster map [K]

       localutctime=name [required]
           Name of time of satellite overpass raster map [local time in UTC]

       temperaturedifference2m=name [required]
           Name of the difference map of temperature from surface skin to about 2 m height [K]

       emissivity=name [required]
           Name of the emissivity map [-]

       transmissivity_singleway=name [required]
           Name of the single-way atmospheric transmissivitymap [-]

       dayofyear=name [required]
           Name of the Day Of Year (DOY) map [-]

       sunzenithangle=name [required]
           Name of the sun zenith angle map [degrees]

       output=name [required]
           Name of the output net radiation layer

DESCRIPTION

       i.eb.netrad  calculates the net radiation at the time of satellite overpass, the way it is
       in the SEBAL model of Bastiaanssen (1995).  It takes input of Albedo, NDVI,  Surface  Skin
       temperature,  time  of  satellite  overpass, surface emissivity, difference of temperature
       from surface skin and about 2 m height (dT), instantaneous satellite  overpass  single-way
       atmospheric transmissivity (tsw), Day of Year (DOY), and sun zenith angle.

NOTES

       In  the old methods, dT was taken as flat images (dT=5.0), if you don’t have a dT map from
       ground data, you would  want  to  try  something  in  this  line,  this  is  to  calculate
       atmospherical  energy balance. In the same way, a standard tsw is used in those equations.
       Refer to r_net.c for that and for other  non-used  equations,  but  stored  in  there  for
       further research convenience.

TODO

       Add more explanations.

REFERENCES

           •   Bastiaanssen, W.G.M., 1995. Regionalization of surface flux densities and moisture
               indicators in composite terrain; a remote sensing approach under  clear  skies  in
               mediterranean climates. PhD thesis, Wageningen Agricultural Univ., The Netherland,
               271 pp.  (PDF)

           •   Chemin, Y., 2012.  A Distributed Benchmarking Framework for Actual ET Models,  in:
               Irmak, A. (Ed.), Evapotranspiration - Remote Sensing and Modeling. InTech.  (PDF)

SEE ALSO

        i.eb.soilheatflux, i.eb.hsebal01, i.albedo

AUTHOR

       Yann Chemin, International Rice Research Institute, The Philippines

SOURCE CODE

       Available at: i.eb.netrad source code (history)

       Accessed: Thursday Aug 01 11:31:31 2024

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

       © 2003-2024 GRASS Development Team, GRASS GIS 8.4.0 Reference Manual