Calculate Relative Humidity from temperature and dew point

Function to calculate relative humidity (%) from temperature (°C) and dew point (°C)

Usage

calcRH_DP(Temp, DewP)

Arguments

Temp: Temperature (°Celsius)
DewP: Td, Dew Point (°Celsius)

Value

Relative Humidity (0-100%)

Details

The relative humidity is calculated using the following equation derived from the August-Roche-Magnus approximation:

$$RH=100\times\frac{\exp\left(\frac{\left(17.625\times DewP\right)}{\left(243.04+DewP\right)}\right)}{\exp\left(\frac{\left(17.625\times Temp\right)}{\left(243.04+Temp\right)}\right)}$$

Where:

RH is the relative humidity in percent
Temp is the air temperature in °C
DewP is the dew point temperature in °C

References

Alduchov, O. A., and R. E. Eskridge, 1996: Improved Magnus' form approximation of saturation vapor pressure. J. Appl. Meteor., 35, 601-609.

https://bmcnoldy.earth.miami.edu/Humidity.html

Examples

# RH at air tempertaure of 20C and dew point of 15°C
calcRH_DP(20, 15)
#> [1] 72.93877

calcRH_DP(20, calcDP(20, 50))
#> [1] 50

head(mydata) |> dplyr::mutate(DewPoint = calcDP(Temp, RH), RH2 = calcRH_DP(Temp, DewPoint))
#> # A tibble: 6 × 7
#>   Site   Sensor Date                 Temp    RH DewPoint   RH2
#>   <chr>  <chr>  <dttm>              <dbl> <dbl>    <dbl> <dbl>
#> 1 London Room 1 2024-01-01 00:00:00  21.8  36.8     6.38  36.8
#> 2 London Room 1 2024-01-01 00:15:00  21.8  36.7     6.34  36.7
#> 3 London Room 1 2024-01-01 00:29:59  21.8  36.6     6.30  36.6
#> 4 London Room 1 2024-01-01 00:44:59  21.7  36.6     6.22  36.6
#> 5 London Room 1 2024-01-01 00:59:59  21.7  36.5     6.18  36.5
#> 6 London Room 1 2024-01-01 01:14:59  21.7  36.2     6.06  36.2