Solar position

Source: R/solar_geometry.R

Solar position

solar_position(
  x,
  UTC = "UTC",
  yday = "yday",
  hour = "hour",
  lon = "lon",
  lat = "lat",
  integral_steps = 1,
  keep.all = TRUE,
  verbose = getOption("merra2.verbose"),
  ...
)

Arguments

x

data.frame with MERRA-2 subset

UTC

name (string) of the column in x with date and time in UTC format

yday

optional name of column in x with the day of the year (consistent with UTC time), will be used if "UTC" is not provided

hour

optional, the name of column with hour of the day (0 to 23, UTC time assumed)

lon

longitude of the location

lat

latitude of the location

integral_steps

integer number of steps for calculation of solar_time, hour_angle, and zenith within an hour, and the logical variable; default is 2 (start and the end of every hour)

keep.all

if TRUE, the interim variables declination, eq_time, solar_time, and hour_angle will be added to x and returned

verbose

Details

List or data.frame with estimated following solar geometry variables:

  • Solar declination (\(\theta_d\)) \[\theta_d = \frac{23.45\pi}{180}\sin{\big(2\pi\frac{284+n}{365}\big)}\]

  • Equation of time (\(E_{qt}\)) \[ E_{qt} = \begin{cases} -14.2\sin{\big(\frac{\pi(n+7)}{111}\big)}& & {1 \leq n \leq 106}\newline 4.0\sin{\big(\frac{\pi(n-106)}{59}\big)}& & {107 \leq n \leq 166}\newline -6.5\sin{\big(\frac{\pi(n-166)}{80}\big)}& & {167 \leq n \leq 246}\newline 16.4\sin{\big(\frac{\pi(n-247)}{113}\big)}& & {247 \leq n \leq 365} \end{cases} \]

  • Apparent solar time (\(T_{solar}\)) \[T_{solar} = T_{UTC}+\frac{E_{qt}}{60}+longitude/15\]

  • Hour angle (\(\theta_{hr}\)) \[\theta_{hr} = \frac{T_{solar}-12}{12}\pi\]

  • Zenith angle \[zenith = \arccos\big({\sin{(latitude)}\sin{(\theta_d)}+\cos{(latitude)}\cos{(\theta_d)}\cos{(\theta_{hr})}\big)}\]

  • Azimuth angle \[ azimuth = \begin{cases} \arcsin{(A)}& & {A \geq 0, B \geq 0}\newline 180-\arcsin{(A)}& & {B < 0}\newline 360+\arcsin{(A)}& & {A < 0, B \geq 0} \end{cases} \] where
    \(n - \text{day of the year}\)
    \(A = \sin{(azimuth)} = -\frac{\sin{(\theta_{hr})}\cos{(\theta_d)}}{\sin{(zenith)}}\)
    \(B = \cos{(azimuth)} = \frac{\sin{(\theta_d)}- \sin{(latitude)}\cos{(zenith)}}{\cos{(latitude)}\sin{(zenith)}}\)

Examples

NA
#> [1] NA