Relative Humidity and Saturation Vapour Pressure

There are two methods to compute relative humidity in thermofeel and these are used together in some index calculations, such as in the UTCI.

How to use

Saturation Vapour Pressure over Water

The input is 2 m air temperature in Kelvin. The output is in hPa.

calculate_saturation_vapour_pressure(2m_temperature)

Relative Humidity Percent

The inputs are 2 m temperature and dew point temperature in Kelvin. The output is a percentage.

calculate_relative_humidity_percent(2m_temperature, 2m_dew_point_temperature)

This uses the Magnus-Tetens saturation vapour pressure (a different empirical form to calculate_saturation_vapour_pressure, which uses Hardy 1998). The result is not clamped: when the dew point exceeds the air temperature (supersaturation) it returns a value above 100%.