evaporation: Evaporation (all methods)
In WDNR-Water-Use/CSLSevap: Evapo(transpi)ration Calculations

Description Usage Arguments Details Value References

Calculates evaporation (mm/day given daily or monthly inputs, or mm/hour given hourly inputs) using specified method. Options include:

FAO: FAO Penman-Montieth reference evapotranspiration (potential evaporation for a reference grass crop) based on Allen et al. (1998) for hourly, daily, or monthly timestep.
McJannet: Daily lake evaporation based on the method in McJannet et al. (2008) as presented in McMahon et al. (2013)
Hamon: Daily lake evaporation based on the unmodified Hamon method as presented in Harwell (2012)

evaporation(
  method = "FAO",
  loc,
  weather,
  lake = NULL,
  albedo = list(ref_crop = 0.23, water = 0.08),
  no_condensation = TRUE,
  rho_a = 1.2,
  ca = 0.001013
)

`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).
`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)
`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).
`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.
`no_condensation`	defaults to TRUE to force negative evapotranspiration values (i.e., condensation) to zero
`rho_a`	density of the air (kg/m^3), defaults to 1.20 kg/m^3 at 20 deg C
`ca`	specific heat of the air (MJ/kg/K), defaults to 0.001013 MJ/kg/K

When assessing which parameters are required for a given method, use the following guidelines:

Input	FAO	McJannet	Hamond
loc	all	all	only phi
weather	all but z0	all	only datetimes & atmp
lake	none, use NULL	all but lst	none, use NULL

evap

a vector with evapo(transpi)ration (mm/hour or mm/day) for each timestep in weather$datetimes

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.

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.

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.

Harwell, G.R., 2012, Estimation of evaporation from open water—A review of selected studies, summary of U.S. Army Corps of Engineers data collection and methods, and evaluation of two methods for estimation of evaporation from five reservoirs in Texas: U.S. Geological Survey Scientific Investigations Report 2012–5202, 96 p.

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