def vapour_pressure_from_absolute_humidity(h, temp):
    """
    Calculates the partial pressure of water vapour for a given absolute air
    humidity and temperature.

    Parameters
    ----------
    h : float
        absolute humidity [kg/m³].
    temp : float
        air temperature [K].

    Returns
    -------
    float
        Partial pressure of water vapour [Pa].

    """
    rw = 461.495 # specific gas constant for water vapour [J / (kg K)]
    return h * temp * rw