ETref                   FAO-56 Penman-Monteith grass reference
                        evapotranspiration
Ra                      Extraterrestrial radiation
Rn                      Net radiation (Rn)
Rnl                     Net longwave radiation (Rnl)
Rns                     Net solar or net shortwave radiation (Rns)
Rso                     Clear-sky solar radiation (Rso)
SolarDec                Solar declination
VP                      Actual vapor pressure
adj_u2                  Adjust wind speed data
constDefaults           Constants
controlDefaults         Control default values
deltaVP                 Slope of the saturation vapor pressure curve
dlh                     Dayligth hours (N)
dr                      Inverse relative distance Earth-Sun
e0                      Saturation Vapor Pressure
estG                    Estimate soil heat flux (G)
estP                    Estimate atmospheric pressure (P)
estRs                   Estimate solar radiation (Rs)
prep.date               Prepare date
psyc_cons               psychrometric constant
satVP                   Saturation Vapor Pressure
w                       Solar time angle
ws                      Sunset hour angle
