sirad (version 2.0-7)

ha: Hargreaves solar radiation model

Description

'ha()' calculates daily solar radiation based on daily temperature range using Hargreaves model.

Usage

ha(days, lat, extraT=NULL, A, B, Tmax, Tmin)

Arguments

days

Vector of class 'Date' of length n.

lat

Latitude in decimal degrees.

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

A

Hargreaves model coefficient 'A'.

B

Hargreaves model coefficient 'B'.

Tmax

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

Tmin

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

Value

• Vector of length n of daily solar radiation [MJm-2].

Details

Hargreaves proposed a method for estimating solar radiation from air temperature measurements.

References

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

See Also

'hacal' to calibrate model using reference data, 'bc' to use Bristow-Campbell model to calculate solar radiation based on temperature range.

Examples

require(zoo)
data(Metdata)
tmax <- Metdata$meteo$TEMP_MAX
tmin <- Metdata$meteo$TEMP_MIN
days <- Metdata$meteo$DAY
lat <- Metdata$LATITUDE
plot(zoo(ha(days=days, lat=lat, extraT=NULL,A=0.17, B=0, Tmax=tmax, Tmin=tmin),order.by=days))