i.eb.netrad(1)

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.

SEE ALSO
i.eb.soilheatflux, i.eb.hsebal01, i.albedo

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)

AUTHOR
Yann Chemin, International Rice Research Institute, The Philippines

SOURCE CODE

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

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