bc: Bristow-Campbell model

In sirad: Functions for Calculating Daily Solar Radiation and Evapotranspiration

Description

'bc' calculates daily solar radiation based on daily temperature range using Bristow-Campbell model.

Usage

bc(days, lat, BCb,extraT=NULL, Tmax, Tmin, BCc = 2, tal)

Arguments

days	Vector of class 'Date' of length n.
lat	Latitude in decimal degrees.
BCb	Bristow-Campbell model coefficient 'B'.
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].
BCc	Bristow-Campbell model coefficient 'C' usually equaled to 2.
tal	Clear sky transmissivity.

Details

Bristow and Campbell proposed a method for estimating solar radiation from air temperature measurements. They developed an empirical relationship to express the daily total atmospheric transmittance as a function of daily range in air temperature.

Value

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

Note

'Tmax', 'Tmin' can contain NA's, but length of vectors 'Tmax', 'Tmin' and 'days' has to be the same.

Author(s)

Jedrzej S. Bojanowski

References

Bristow, K.L., Campbell, G.S. 1984. On the relationship between incoming solar radiation and daily maximum and minimum temperature. Agriculture and Forest Meteorology, 31:159-166.

See Also

'bccal' to calibrate model using reference data, 'bcauto' to perform auto-calibration, and 'ha' to use Hargreaves model to calculate solar radiation based on temperature range.

Examples

require(zoo)
data(Metdata)
B <- 0.11
tmax <- Metdata$meteo$TEMP_MAX
tmin <- Metdata$meteo$TEMP_MIN
days <- Metdata$meteo$DAY
lat <- Metdata$LATITUDE
plot(zoo(bc(days, lat, BCb=B,extraT=NULL, tmax, tmin, BCc=2, tal=0.76),order.by=days))

Example output

Loading required package: zoo

Attaching package: 'zoo'

The following objects are masked from 'package:base':

    as.Date, as.Date.numeric

sirad documentation built on May 1, 2019, 7:42 p.m.