MeTo (version 0.1.1)

Ra: Extraterrestrial radiation

Description

Extraterrestrial radiation [MJ/(m2 time)] in dependence to time, latitude and longitude.

Usage

Ra(x, lat.rad = NULL, lat.deg = NULL, long.deg, tl, control = list(Lz = 345))

Arguments

x

date-time object or day of the year (must be date-time object if calculation period is smaller 1 day)

lat.rad

latitude [rad]. Use either lat.rad or lat.deg. Latitude is positive for the northern hemisphere and negative for the southern hemisphere

lat.deg

latitude [degree]. Use either lat.deg or lat.rad. Latitude is positive for the northern hemisphere and negative for the southern hemisphere

long.deg

longitude of the measurement site (degrees east of Greenwich) (only needed for periods shorter 1 day)

tl

length of calculation period [hour] (1 for hourly period, 0.5 for a 30-minute period or 24 for daily period). Only needed if x is date-time object with length of 1.

control

list for control parameters and empirical factors defined in controlDefaults and constDefaults (see Details)

Details

References

Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). Crop evapotranspiration-Guidelines for computing crop water requirements-FAO Irrigation and drainage paper 56. FAO, Rome, 300(9).

Examples

# NOT RUN {
# --------------------------------------------
#  Daily period
# --------------------------------------------

Ra(x = 105, lat.deg = 13.73)

# --------------------------------------------
#  Hourly period
# --------------------------------------------

Ra(x = as.POSIXct(c('2018-10-01 14:30', '2018-10-01 15:30')),
   lat.deg = 16.21, long.deg = 343.75, control = list(Lz = 15))

Ra(x = as.POSIXct('2018-10-01 14:30'), tl = 1,
   lat.deg = 16.21, long.deg = 343.75, control = list(Lz = 15))

# }