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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

       Last changed: $Date: 2015-02-27 12:03:54 +0100 (Fri, 27 Feb 2015) $

SOURCE CODE

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

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