NAME

       i.eb.soilheatflux  - Soil heat flux approximation (Bastiaanssen, 1995).

KEYWORDS

       imagery, energy balance, soil heat flux, SEBAL

SYNOPSIS

       i.eb.soilheatflux
       i.eb.soilheatflux --help
       i.eb.soilheatflux   [-r]   albedo=name  ndvi=name  temperature=name  netradiation=name  localutctime=name
       output=name  [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -r
           HAPEX-Sahel empirical correction (Roerink, 1995)

       --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]

       netradiation=name [required]
           Name of Net Radiation raster map [W/m2]

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

       output=name [required]
           Name for output raster map

DESCRIPTION

       i.eb.soilheatflux calculates the soil heat flux approximation (g0) after Bastiaanssen  (1995).  The  main
       reference  for  implementation  is  Alexandridis,  2009.   It  takes  input of Albedo, NDVI, Surface Skin
       temperature, Net Radiation (see r.sun), time of satellite overpass, and a flag for the Roerink  empirical
       modification  from  the  HAPEX-Sahel experiment.  The "time of satellite overpass" map can be obtained as
       follows:

           •   MODIS: a related sub dataset is included in each HDF file, and simply to be imported as a  raster
               map;

           •   Landsat:  to  be  generated  as  map from the overpass time stored in the metadata file (given in
               Greenwich Mean Time - GMT), see below.
       For Landsat, the overpass map can be computed by using a two-step method:
       # 1) extract the overpass time in GMT from metadata file
       i.landsat.toar -p input=dummy output=dummy2 \
          metfile=LC81250452013338LGN00_MTL.txt lsatmet=time
       # ... in this example approx. 03:12am GMT
       # 2) create map for computational region of Landsat scene
       g.region rast=LC81250452013338LGN00_B4 -p
       r.mapcalc "overpasstime = 3.211328"

SEE ALSO

        r.sun, i.albedo, i.emissivity, i.eb.hsebal01, i.eb.evapfr i.landsat.toar

REFERENCES

       Bastiaanssen, W.G.M., 1995.  Estimation of Land surface parameters  by  remote  sensing  under  clear-sky
       conditions. PhD thesis, Wageningen University, Wageningen, The Netherlands.  (PDF)

       Chemin  Y.,  Alexandridis  T.A.,  2001. Improving spatial resolution of ET seasonal for irrigated rice in
       Zhanghe, China. Asian Journal of Geoinformatics. 5(1):3-11,2004.

       Alexandridis T.K., Cherif I., Chemin Y., Silleos N.G., Stavrinos E., Zalidis G.C. Integrated  methodology
       for estimating water use in Mediterranean agricultural areas. Remote Sensing. 2009, 1, 445-465.  (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, Asian Institute of Technology, Thailand

SOURCE CODE

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

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