i.eb.soilheatfluxgrass - Online in the Cloud

PROGRAM:

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"

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