heat_flux: Heat flux
In WDNR-Water-Use/CSLSevap: Evapo(transpi)ration Calculations

Description Usage Arguments Value References

Calculates the heat flux for the land surface in question. When using the "FAO" evaporation method, calculates the soil heat flux beneath a dense cover of grass based on Equations 42-46 in Allen et al. (1998). When using the "McJannet" lake evaporation method, calculates the change in heat storage based on water temperature following McJannet et al. (2008) Equation 31 as presented in McMahon et al. S11.33 (2013).

heat_flux(
  method,
  loc,
  lake,
  weather,
  albedo,
  Rn = NULL,
  rho_w = 997.9,
  cw = 0.00419
)

`method`	denotes which evaporation method to use ("FAO", "McJannet", or "Hamon").
`loc`	a list with location information that includes: z: elevation above mean sea level (m) phi: latitude of location (radians). Positive for northern hemisphere, negative for southern hemisphere. Lm: longitude of location (degrees west of Greenwich). Lz: longitude of location's measurement timezone (degrees west of Greenwich). For example, Lz = 75, 90, 105 and 120° for measurement times based on the Eastern, Central, Rocky Mountain and Pacific time zones (United States) and Lz = 0° for Greenwich, 330° for Cairo (Egypt), and 255° for Bangkok (Thailand).
`lake`	A list with lake data. Defaults to NULL, but for McJannet lake evaporation calculations, should include: A: surface area of the lake (km^2). depth_m: depth of the lake (m). Can be a static value or vector corresponding with datetimes vector. lst: optional data frame with date (datetime) and ltmp (lake temperature, degC). wtmp0: required initial water temperature for first day in datetimes (degC).
`weather`	a list with weather data that includes: dt: string indicating the timestep of input weather series. Expects "hourly", "daily", or "monthly". datetimes: datetimes of weather records POSIXct. If monthly timestep, make sure date is the 15th of each month. atmp: If hourly timestep, vector of air temperature (degrees C) corresponding with datetimes vector. If daily or monthly timestep, list with two vectors, "min" and "max", with mean daily min and max air temperature (degrees C) corresponding with datetimes vector RH: If hourly timestep, vector of relative humidity (percent) corresponding with datetimes vector. If daily or monthly timestep, list with two vectors, "min" and "max", with mean daily min and max relative humidity (percent) corresponding with datetimes vector. Rs: vector of incoming solar or shortwave radiation (MJ/m^2/hr if hourly timestep, MG/m^2/day if daily or monthly), corresponding with datetimes vector. wind: vector with mean wind speed (m/s), corresponding with datetimes vector. wind_elev: atomic number, height at which wind is measured (m) z0: aerodynamic roughness of weather measurement site (m)
`albedo`	a list with albedos for different surfaces, defaults to: ref_crop: albedo of the hypothetical grass reference crop, 0.23 water: albedo of water, 0.08.
`Rn`	Net solar or shortwave radiation (MJ/m^2/timestep)
`rho_w`	density of water (kg/m^3), defaults to 997.9 kg/m^3 at 20 deg C
`cw`	specific heat of water (MJ/kg/K), defaults to 0.00419

`G`	heat flux (MJ/m^2/hr)

Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). Crop evapotranspiration: Guidelines for computing crop water requirements. Rome: FAO. Retrieved from http://www.fao.org/docrep/X0490E/x0490e00.htm.

McMahon, T. A., Peel, M. C., Lowe, L., Srikanthan, R., and McVicar, T. R. (2013). Estimating actual, potential, reference crop and pan evaporation using standard meteorological data: a pragmatic synthesis, Hydrol. Earth Syst. Sci., 17, 1331–1363. https://doi.org/10.5194/hess-17-1331-2013.

McJannet, D. L., Webster, I. T., Stenson, M. P., and Sherman, B.S. (2008). Estimating open water evaporation for the Murray-Darling Basin. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project, CSIRO, Australia, 50 pp. Retrieved from http://www.clw.csiro.au/publications/waterforahealthycountry/mdbsy/technical/U-OpenWaterEvaporation.pdf.

WDNR-Water-Use/CSLSevap documentation built on April 9, 2021, 1:35 a.m.