## NAME

i.eb.hsebal01 - Computes sensible heat flux iteration SEBAL 01.

## KEYWORDS

imagery, energy balance, soil moisture, evaporative fraction, SEBAL

## SYNOPSIS

i.eb.hsebal01
i.eb.hsebal01 --help
i.eb.hsebal01 [-ac] netradiation=name soilheatflux=name aerodynresistance=name temperaturemeansealevel=name vapourpressureactual=name frictionvelocitystar=float [row_wet_pixel=float] [column_wet_pixel=float] [row_dry_pixel=float] [column_dry_pixel=float] output=name [--overwrite] [--help] [--verbose] [--quiet] [--ui]

### Flags:

-a
  Automatic wet/dry pixel (careful!)
-c
  Dry/Wet pixels coordinates are in image projection, not row/col
--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:

netradiation=name [required]
  Name of instantaneous net radiation raster map [W/m2]
soilheatflux=name [required]
  Name of instantaneous soil heat flux raster map [W/m2]
aerodynresistance=name [required]
  Name of aerodynamic resistance to heat momentum raster map [s/m]
temperaturemeansealevel=name [required]
  Name of altitude corrected surface temperature raster map [K]
vapourpressureactual=name [required]
  Name of the actual vapour pressure (e_act) map [KPa]
frictionvelocitystar=float [required]
  Value of the height independent friction velocity (u*) [m/s]
  Default: 0.32407
row_wet_pixel=float
  Row value of the wet pixel
column_wet_pixel=float
  Column value of the wet pixel
row_dry_pixel=float
  Row value of the dry pixel
column_dry_pixel=float
  Column value of the dry pixel
output=name [required]
  Name for output sensible heat flux raster map [W/m2]

## DESCRIPTION

i.eb.hsebal01 will calculate the sensible heat flux map (h0), given both maps of Net Radiation and soil Heat flux (Rn, g0) at instantaneous time, the surface roughness (z0m), a map of the altitude corrected temperature (t0dem), a point data of the frictional velocity (u*), a value of actual vapour pressure (ea[KPa]) and the (x,y) pairs for wet and dry pixels. Full process will need those:

- i.vi, i.albedo, r.latlong, i.emissivity
- i.evapo.potrad (GRASS Addon)
- i.eb.netrad, i.eb.soilheatflux, i.eb.hsebal01
- i.eb.evapfr, i.eb.eta

(for time integration: i.evapo.time_integration)

i.eb.hsebal01 performs the computation of sensible heat flux [W/m2] after Bastiaanssen, 1995 in [1], used in this form in 2001 by [2]. Implemented in this code in [3].

## NOTES

- z0m can be alculated by i.eb.z0m or i.eb.z0m0 (GRASS Addons).
- ea can be calculated with standard meteorological data.
  eoTmin=0.6108*EXP(17.27*Tmin/(Tmin+237.3))
  eoTmax=0.6108*EXP(17.27*Tmax/(Tmax+237.3))
  ea=(RH/100)/((eoTmin+eoTmax)/2)
- t0dem = surface temperature + (altitude * 0.627 / 100)

## REFERENCES

[1] 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)

[2] 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.

[3] 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)

[4] 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.evapfr

## AUTHOR

Yann Chemin, International Rice Research Institute, Los Banos, The Philippines.

Contact: Yann Chemin

## SOURCE CODE

Available at: i.eb.hsebal01 source code (history)

Latest change: Thursday Jan 26 14:10:26 2023 in commit: cdd84c130cea04b204479e2efdc75c742efc4843

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