weather-formulas
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A collection of atmospheric, meteorological weather calculations
92 lines (91 loc) • 3.43 kB
JavaScript
"use strict";
var __importDefault = (this && this.__importDefault) || function (mod) {
return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
const constants_1 = __importDefault(require('../constants.cjs'));
/**
* 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 - constants_1.default.KELVIN)) / (243.04 + (dewPoint - constants_1.default.KELVIN))) /
Math.exp((17.625 * (temperature - constants_1.default.KELVIN)) / (243.04 + (temperature - constants_1.default.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 = constants_1.default.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 - constants_1.default.KELVIN)) / ((T - constants_1.default.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 - constants_1.default.KELVIN)) / (243.12 + (T - constants_1.default.KELVIN)));
}
exports.default = {
relativeHumidity,
absoluteHumidity,
absoluteHumidityByRelativeHumidity,
mixingRatio,
vaporPressure,
saturationVaporPressure,
specificHumidity
};