hour_angle: Solar time angle

In WDNR-Water-Use/CSLSevap: Evapo(transpi)ration Calculations

Description

Calculates the beginning, midpoint, and end solar time angle (radians) for a given location and day of the year using Equations 29-33 from Allen et al. (1998). Used for calculations at an hourly or shorter timestep.

Usage

hour_angle(tmid, tL, Lm, Lz)

Arguments

tmid	date and time of the midpoint of the time period POSIXct.
tL	length of the time period, from lubridate function "interval_len".
Lm	longitude of the measurement site (degrees west of Greenwich).
Lz	longitude of the center of the time zone used for measurements (degrees west of Greenwich). For example, Lz = 75, 90, 105 and 120° for the Eastern, Central, Rocky Mountain and Pacific time zones (United States) and Lz = 0° for Greenwich, 330° for Cairo (Egypt), and 255° for Bangkok (Thailand).

Value

omega1	solar time angle at the beginning of the period (radians)
omega2	solar time angle at the end of the period (radians)

References

Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). Crop evapotranspiration: Guidelines for computing crop water requirements. Rome: FAO. Retrieved from http://www.fao.org/docrep/X0490E/x0490e00.htm.

WDNR-Water-Use/CSLSevap documentation built on April 9, 2021, 1:35 a.m.