I develop a package 'sirad' which collects methods for estimating daily surface solar radiation and evapotranspiration based on the meteorological variables.

ap Angstrom-Prescott solar radiation model
apcal Calibrate Angstrom-Prescott model
bc Bristow-Campbell model
bcauto Auto-calibrate Bristow-Campbell model
bccal Calibrate Bristow-Campbell model
cst Estimate clear sky transmissivity
ha Hargreaves solar radiation model
hauto Auto-calibrate Hargreaves model
hacal Calibrate Hargreaves model
et0 FAO Penman-Monteith evapotranspiration equation
mh Mahmood-Hubbard solar radiation model
modeval Estimators of the model performance
su Supit-Van Kappel solar radiation model
sucal Calibrate Supit-Van Kappel model

The last stable release of 'sirad' is hosted on CRAN.

The development version is available on R-forge and can be installed directly from R using:
install.packages("sirad", repos="http://r-forge.r-project.org")

Since the manual of 'sirad' is still in preparation, do not hesitate to contact me if you would
need more examples of how to use the package.