HumidityCalculator.py

HumidityCalculator.py

import math 

class HumidityCalculator:
    def calculate_absolute_humidity(
        self, 
        relative_humidity: float, 
        temperature: float, 
        temperature_in_fahrenheit: bool = False, 
        is_relative_humidity_in_percent: bool = True
    ) -> float:
        """
        Computes absolute humidity from relative humidity and temperature.
        Based on the August-Roche-Magnus approximation.
        Considered valid when:
          0 < temperature < 60 degrees Celsius
          1% < relative humidity < 100%
          0 < dew point < 50 degrees Celsius
        
        Args:
            relative_humidity: The relative humidity value to be converted.
            temperature: Temperature associated with given relative humidity value in Fahrenheit or Celsius.
            temperature_in_fahrenheit: Is the given temperature in Fahrenheit or Celsius? Default is Celsius.
            is_relative_humidity_in_percent: Is the given relative humidity in percent or decimal form?
        
        Returns:
            The absolute humidity in grams per cubic meter (g/m³).
        
        Raises:
            ValueError: If the input values are outside the acceptable range.
        """
        # Constants
        kSVP = 6.112  # Saturated vapor pressure in millibars
        kMolecularWeight = 18.01528  # Molecular weight of water in g/mol
        kA = 17.625  # Alduchov-Eskeridge coefficient A
        kB = 243.05  # Alduchov-Eskeridge coefficient B

        # Check and convert relative humidity if in percent
        if is_relative_humidity_in_percent:
            if relative_humidity < 1 or relative_humidity > 100:
                raise ValueError("Relative Humidity In Percent must be between 1 and 100")
            relative_humidity /= 100.0
        elif relative_humidity < 0.01 or relative_humidity > 1:
            raise ValueError("Relative Humidity must be between 0.01 and 1.0")

        # Convert temperature to Celsius if in Fahrenheit
        temperature_in_celsius = temperature
        if temperature_in_fahrenheit:
            temperature_in_celsius = (temperature - 32) / 1.8000

        # Validate temperature range
        if temperature_in_celsius < 1 or temperature_in_celsius > 60:
            raise ValueError("Temperature In Celsius must be between 1 and 60")

        # Calculate absolute humidity
        temperature_in_kelvin = temperature_in_celsius + 273.15
        pressure = kSVP * math.exp((kA * temperature_in_celsius) / (temperature_in_celsius + kB)) * relative_humidity
        water_vapor_in_mols = pressure / (temperature_in_kelvin * 0.08314)

        return water_vapor_in_mols * kMolecularWeight  # g/m³


if __name__ == "__main__":
    humcalc = HumidityCalculator()
    print(humcalc.calculate_absolute_humidity(50.0, 30.0, False, True))