Relative optical air mass — trans_air_mass

Calculates the relative optical air mass.

Usage

trans_air_mass_rel(...)

# Default S3 method
trans_air_mass_rel(datetime, lon, lat, ...)

# S3 method for class 'weather_station'
trans_air_mass_rel(weather_station, ...)

Arguments

...: Additional arguments.
datetime: POSIXlt object, date and time of the observation.
lon: Longitude in decimal degrees.
lat: Latitude in decimal degrees.
weather_station: A weather_station object.

Value

Relative optical air mass, unitless.

Details

The relative optical air mass is calculated using the formula: $$M_{rel} = \frac{1}{\sin(elevation) + 1.5 \cdot elevation^{-0.72}}$$ where $elevation$ is the solar elevation angle in degrees. The formula is only evaluated for positive solar elevation; below-horizon or invalid elevations return NA with a warning. The air-mass approximation is cited to Bendix (2004) appendix material.

References

Bendix 2004, p. 246.

Examples

# Calculate relative optical air mass
trans_air_mass_rel(
  datetime = as.POSIXlt("2023-08-06 12:00:00", tz = "UTC"),
  lon = 8.68, lat = 50.77
)
#> [1] 1.096104