Module: WrfLibrary::Measurand::RelativeHumidity

Defined in:

lib/wrf_library/measurand/relative_humidity.rb

Overview

module to calculate the relative humidity for a given temperature, pressure and humidity.

Class Method Summary

• .calculate_relative_humidity(temperature, pressure, humidity) ⇒ Float

  calculates the relative humidity.

• .calculate_saturation_pressure(temperature) ⇒ Float

  calculates the water vapour pressure.

Class Method Details

.calculate_relative_humidity(temperature, pressure, humidity) ⇒ Float

calculates the relative humidity

Parameters:

• temperature (Float) —

  the air temperature in degree celcius

• humidity (Float) —

  the vapor mixing ratio in kg/kg

• pressure (Float) —

  the air pressure in hectopascal

Returns:

• (Float) —

  the relative humidity in %

# File 'lib/wrf_library/measurand/relative_humidity.rb', line 13

def self.calculate_relative_humidity(temperature, pressure, humidity)
  saturation_pressure = calculate_saturation_pressure(temperature)
  partial_pressure = 0.622 * saturation_pressure / pressure
  rel_hum_pre = humidity * 100 / partial_pressure
  [ rel_hum_pre, 100.0 ].min
end

.calculate_saturation_pressure(temperature) ⇒ Float

calculates the water vapour pressure

Parameters:

• temperature (Float) —

  the air temperature in degree celsius

Returns:

• (Float) —

  the water vapour pressure

# File 'lib/wrf_library/measurand/relative_humidity.rb', line 23

def self.calculate_saturation_pressure(temperature)
  6.1094 * Math.exp((17.685 * temperature) / (temperature + 243.04))
end