sirad (version 2.0-2)

hacal: Calibrate Hargreaves model

Description

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

Usage

hacal(lat, days, rad_mea, 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].

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:
• Ha
  Hargreaves 'A' coefficient
• Hb
  Hargreaves 'B' coefficient
• Hr2
  Coefficient of determination of performed linear regression

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,tmax=tmax, tmin=tmin)