sirad (version 2.3-3)

hacal: Calibrate Hargreaves model

Description

Function estimates Hargreaves model coefficients 'A' and 'B' based on reference data

Usage

hacal(lat, days, rad_mea, extraT=NULL,tmax, tmin)

Arguments

lat

Latitude in decimal degrees.

days

Vector of class 'Date' of length n.

rad_mea

Vector of length n containing reference (e.g. measured) solar radiation [MJm-2].

extraT

Optional. Vector of length n of extraterrestrial solar radiation [MJm-2]. If 'NULL' then it is calculated by the function. Providing extraterrestrial solar radiation speeds up the computation

tmax

Vector of length n containing daily maximum temperature [C].

tmin

Vector of length n containing daily minumum temperature [C].

Value

Vector of length 3 containing: Vector of length 3 containing:

Details

Function estimates Hargreaves model coefficients 'A' and 'B' based on reference (e.g. measured) solar radiation data. It performs a linear regression.

References

Hargreaves, G.H., Samini, Z.A. 1892. Estimating potential evapotranspiration. J. Irrig. Darin. Eng., ASCE 108 (3), 225-230.

See Also

'ha'

Examples

data(Metdata)
tmax <- Metdata$meteo$TEMP_MAX
tmin <- Metdata$meteo$TEMP_MIN
days <- Metdata$meteo$DAY
lat <- Metdata$LATITUDE
rad_mea <- Metdata$meteo$RAD_MEA
hacal(lat=lat,days=days,rad_mea,extraT=NULL,tmax=tmax, tmin=tmin)