Transmittance due to water vapor

Calculates transmittance due to water vapor.

Usage

trans_vapor(...)

# Default S3 method
trans_vapor(datetime, lon, lat, elev, temp, ...)

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

Arguments

...

Additional arguments.

datetime

POSIXlt object, date and time of the observation.

lon

Longitude in decimal degrees.

lat

Latitude in decimal degrees.

elev

Elevation above sea level in meters.

temp

Air temperature in °C.

weather_station

A weather_station object.

Value

Transmittance ratio from 0 to 1, unitless.

Details

The transmittance due to water vapor is calculated using the formula: $$T_{vapor} = 1 - 2.4959 \cdot x \cdot ((1 + 79.034 \cdot x)^{0.6828} + 6.385 \cdot x)^{-1}$$ where \(x\) is the product of the precipitable water and the relative optical air mass. This is an Iqbal-style atmospheric transmittance approximation as presented in the Bendix (2004) appendix material cited for the package.

References

Bendix 2004, p. 245.

Examples

# Calculate transmittance due to water vapor
trans_vapor(
  datetime = as.POSIXlt("2023-08-06 12:00:00", tz = "UTC"),
  lon = 8.68, lat = 50.77, elev = 100, temp = 20
)
#> [1] 0.8373115