Calculate Dew Point

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

Usage

calcDP(Temp, RH)

Arguments

Temp

Temperature (°Celsius)

RH

Relative Humidity (0-100%)

Value

Td, Dew Point (°Celsius)

Details

The dew point is calculated using the following equation derived from the August-Roche-Magnus approximation:

$$T_d\left(DewP\right)=\frac{234.04\times\log\left(\frac{RH}{100}\right)+\frac{17.625\times Temp}{243.04+Temp}}{17.625-\log\left(\frac{RH}{100}\right)-\frac{17.625\times Temp}{243.04+Temp}}$$

Where:

• T_d is the dew point temperature in degrees Celsius.

• Temp is the air temperature in degrees Celsius.

• RH is the relative humidity in percent.

Calculation is valid for:

• 0°C < T < 60°C

• 1% < RH < 100%

• 0°C < Td < 50°C

Note

The Arden Buck equation is also available in the source R code.

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

See also

calcTemp for calculating temperature

calcRH_DP for calculating relative humidity from dew point

calcDP for calculating dew point

calcRH_AH for calculating relative humidity from absolute humidity

Examples

calcDP(20, 50)
#> [1] 9.261107

calcDP(20, calcRH_AH(20, calcAH(20, 50)))
#> [1] 9.261107

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