r2dRue (version 1.0.3)

solarRad: Computes extra-terrestrial solar radiation

Description

solarRad computes the solar radiation received at the top of the Earth's atmosphere on a horizontal surface. This radiation will change during the day and will be different at different latitudes and in different seasons.

Usage

solarRad(img, day)
solarRad12M(img, outFl, ...)

Arguments

img

object of class SpatialGridDataFrame that provided a projection class and a bbox attributes. The nature of the data.frame that contains the attribute data is not relevant. It must be in geographic coordinates.

day

The number of the day (from 1 to 365) to compute extra-terrestrial radiation.

outFl

A list of 12 file names to save the results.

...

Any unmatched parameter will be passed to the writeGDAL routine.

Value

• solarRad returns a single image corresponding to the specified day, as a SpatialGridDataFrame class. solarRad12M writes 12 images to disk in the format especified by the GDAL drivername parameter.

Details

The output is expressed in cal/cm2*day. This function runs unnoticed within petHgsm, but can be executed manually.

References

Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56

See Also

petHgsm

Examples

#not run
#aux=readGDAL('iberia_mask')
#calc the extraterrestial radiation the 15-agost
#Rad=solarRad(aux,227)
#writeGDAL(Rad,'solarrad_15ago')
#or to calculate and write to disk, the radiation of the twelve months
#RadFileNames=paste('rad',month.abb,sep='')
#solarRad12M(img,RadFileNames)