ETo: 24 Hour FAO 56 and ASCE-EWRI Reference Evapotranspiration ETo

In gowusu/sebkc: The Surface Energy Balance and Crop Coefficient Estimation with R

24 Hour FAO 56 and ASCE-EWRI Reference Evapotranspiration ETo

Description

24 Hour FAO 56 and ASCE-EWRI Reference Evapotranspiration ETo

Usage

ETo(Tmax, Tmin, DOY, latitude, longitude = NULL, z = NULL, uz = 2,
  altitude = NULL, RHmax = NULL, RHmin = NULL, n = NULL, Krs = 0.16,
  albedo = 0.23, as = 0.25, bs = 0.5, Rs = NULL, Rn = NULL, G = 0,
  EF = NULL, wmo = NULL, airport = NULL, scale = "sine function",
  Kc = NULL, surface = "grass")

## Default S3 method:
ETo(Tmax, Tmin, DOY, latitude, longitude = NULL, z = NULL,
  uz = 2, altitude = NULL, RHmax = NULL, RHmin = NULL, n = NULL,
  Krs = 0.16, albedo = 0.23, as = 0.25, bs = 0.5, Rs = NULL,
  Rn = NULL, G = 0, EF = NULL, wmo = NULL, airport = NULL,
  scale = "evaporative fraction", Kc = NULL, surface = "grass")

Arguments

Tmax	Numeric. Maximum air Temperature in degree Celsius
Tmin	Numeric. Minimum air Temperature in degree Celsius
DOY	Numeric or Date [YYYY-mm-dd]. Day of the Year. If you give data in the form of date [YYYY-mm-dd], it will be converted to DOY
latitude	geographical coordinates in decimal degrees. It should be negative for southern hemisphere
longitude	The longitude of the measurement site i.e. geographical coordinates in decimal degrees for the weather station. It should be negative for West and positive for East.
z	The height above surface where wind speed was measured, in metres.
uz	The wind speed in m/s
altitude	The elevation of the weather station, in metres
RHmax	Maximum Relative Humidity in percent
RHmin	Minimum Relative Humidity in percent
n	Sunshine hours
Krs	Relationship between the fraction of extraterrestrial radiation that reaches the earth's surface, Rs/Ra, and the air temperature difference Tmax - Tmin for interior (Krs = 0.16) and coastal (Krs = 0.19) regions
albedo	albedo values. For grass it is 0.23[dimensionless]
as	Regression constant, intercept, expressing the fraction of extra-terrestrial radiation reaching the earth on overcast days (n = 0); either a calibrated value or as = 0.25 can be used.
bs	regression constant, slope, expressing the fraction of extraterrestrial radiation reaching the earth on overcast days (n = 0); either a calibrated value or bs = 0.5 can be used.
Rs	shortwave incoming radiation [MJ/m2/day]
Rn	Net daily radiation in MJ/m2/day. If it is NULL, it will be computed
G	Daily Soil heat flux in W/m2
EF	Spatial. ET fraction [-] from sebal or tseb sebs. It is advisable to link it to any of the two functions.
wmo	numeric. World Meteorological Organization weather station code. You can use the Worldwide Station List at https://www.wunderground.com/about/faq/international_cities.asp [Accessed on 2016-5-6] or http://www.wetterzentrale.de/klima/stnlst.html [Accessed on 2016-5-6]
airport	numeric. IATA or ICAO code. They are alphabetically listed at https://en.wikipedia.org/wiki/List_of_airports_by_IATA_code:_A [Accessed on 2016-5-6]
scale	character The type of scale models to upscale instantaneous ET to daily ET. it takes "Evaporative Fraction" (Bastiaanssen et al 1998); "Sine Function" (Jackson et al 1983); "Solar Radiation" (French et al 2005). Remember the blank spaces between the parameters. You can also respectively use "evaporative" or "solar" or "sine".
Kc	Crop coefficient
surface	character. It is either "grass" or "alfalfa"

Value

• ETo: 24 hour reference ETo [mm/day]

• ETa: 24 hour actual ET. It is not NULL if EF has a numeric value

• ETc: 24 hour crop ET. It is not NULL if Kc has a numeric value

• Rn: Net daily Radiation [W/m2]

• Rn_mj_m2_day: Net daily Radiation [MJ/m2/day]

• y: psychrometric constant [kPa/degree Celsius]

• slope: slope of saturation vapour pressure curve [kPa/degree Celsius]

• vpd: Vapour pressure deficit[kPa]

Author(s)

George Owusu

References

ALLEN, R. G., PEREIRA, L. S., RAES, D., & SMITH, M. 1996. Crop Evapotranspiration (guidelines for computing crop water requirements) FAO Irrigation and Drainage Paper No. 56: FAO.

See Also

ETohr

Examples

## Not run: 
#with minimal data
PET=ETo(Tmax=31,Tmin=28,latitude=5.6,DOY="6-2-2001")
PET$ETo
#with enough data as in FAO56 EXAMPLE 18 on 6 July in Uccle (Brussels, Belgium) 
#located at 50 degrees 48 minutes N and at 100 m above sea level
PET24=ETo(Tmax=21.5,Tmin=12.3,z=10,uz=2.78,altitude=100,
RHmax=84,RHmin=63,n=9.25,DOY=187,latitude=50.8)
PET24$ETo

## End(Not run)

gowusu/sebkc documentation built on July 28, 2023, 11:44 a.m.