weather-formulas/dist/esm/formulas/humidity.js

A collection of atmospheric, meteorological weather calculations

import c from '../constants.js';
/**
 * Calculate Relative Humidity
 * @param {number} temperature Temperature in K (Kelvin)
 * @param {number} dewPoint Dew Point in K (Kelvin)
 * @returns {number} Relative Humidity in percentage (%)
 */
function relativeHumidity(temperature, dewPoint) {
    const RH = 100 * (Math.exp((17.625 * (dewPoint - c.KELVIN)) / (243.04 + (dewPoint - c.KELVIN))) /
        Math.exp((17.625 * (temperature - c.KELVIN)) / (243.04 + (temperature - c.KELVIN))));
    return RH;
}
/**
 *
 * @param mH20 Mass of water vapor g/m3
 * @param Vnet Volume of air (m3)
 * @returns
 */
function absoluteHumidity(mH2O, Vnet) {
    if (Vnet <= 0) {
        throw new Error("Vnet must be greater than 0 to avoid division by zero.");
    }
    const AH = mH2O / Vnet; // AH: absolute humidity (mass of water vapor per unit volume)
    return AH;
}
/**
 *
 * @param RH Relative humidity %
 * @param T Temperature in Kelvin
 * @returns Absolute Humidity
 */
function absoluteHumidityByRelativeHumidity(RH, T) {
    const M_w = 18.015; // g/mol - Molar mass of water vapor
    const R = c.DEFAULT_ATMOSPHERIC_CONSTANTS.gasConstant; // J/(mol·K) - Universal gas constant
    // Calculate saturation vapor pressure (Pa)
    const P_sat = saturationVaporPressure(T);
    // Convert RH from percentage to fraction
    const RH_fraction = RH / 100;
    // Calculate absolute humidity (g/m³)
    const AH = (RH_fraction * P_sat * M_w) / (R * T);
    return AH;
}
/**
 * Calculate Specific Humidity
 * @param {number} mixingRatio Mixing Ratio in g/kg (grams per kilogram)
 * @returns {number} Specific Humidity in kg/kg (kilograms per kilogram)
 */
function specificHumidity(mixingRatio) {
    return mixingRatio / (1 + mixingRatio);
}
/**
 * Calculate Mixing Ratio
 * @param {number} vaporPressure Vapor Pressure in Pa (Pascal)
 * @param {number} pressure Pressure in Pa (Pascal)
 * @returns {number} Mixing Ratio in g/kg (grams per kilogram)
 */
function mixingRatio(vaporPressure, pressure) {
    return (0.622 * vaporPressure) / (pressure - vaporPressure) * 1000;
}
/**
 * Calculate Vapor Pressure using the Clausius-Clapeyron equation.
 * @param {number} temperature Temperature in K (Kelvin)
 * @returns {number} Vapor Pressure in Pa (Pascal)
 */
function vaporPressure(temperature) {
    const T = temperature; // Keep temperature in Kelvin
    return 611.2 * Math.exp((17.67 * (T - c.KELVIN)) / ((T - c.KELVIN) + 243.5));
}
/**
 * Calculate Saturation Vapor Pressure using the Clausius-Clapeyron equation.
 * @param {number} temperature Temperature in K (Kelvin)
 * @returns {number} Saturation Vapor Pressure in Pa (Pascal)
 */
function saturationVaporPressure(temperature) {
    const T = temperature; // Keep temperature in Kelvin
    return 611.2 * Math.exp((17.62 * (T - c.KELVIN)) / (243.12 + (T - c.KELVIN)));
}
export default {
    relativeHumidity,
    absoluteHumidity,
    absoluteHumidityByRelativeHumidity,
    mixingRatio,
    vaporPressure,
    saturationVaporPressure,
    specificHumidity
};