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add documentation and remove obsolete
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@oyve
oyve committed Nov 11, 2020
1 parent 0755136 commit 13e3e14
Showing 1 changed file with 119 additions and 60 deletions.
179 changes: 119 additions & 60 deletions temperature.js
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Original file line number Diff line number Diff line change
@@ -1,16 +1,4 @@
'use strict'

//This code uses formulas and valuations derived from several Wikipedia articles:
//
//https://en.wikipedia.org/wiki/Dew_point
//https://en.wikipedia.org/wiki/Wind_chill#North_American_and_United_Kingdom_wind_chill_index
//https://en.wikipedia.org/wiki/Wind_chill#Australian_apparent_temperature
//https://en.wikipedia.org/wiki/Heat_index
//https://en.wikipedia.org/wiki/Humidex
//
//most variable names have been kept from the Wikipedia article to ease the reading.


const KELVIN = 273.15;

const DEW_POINT_VALUATIONS = {
Expand All @@ -22,22 +10,32 @@ const DEW_POINT_VALUATIONS = {
ARDENBUCK_MINUS: { a: 6.1121, b: 17.966, c: 247.15, d: 234.5 } //for −40 °C ≤ T ≤ 0 °C (error ≤ 0.06%).
};


function dewPointValuationsByTemperature(temperatureC) {
if (temperatureC < 0) {
/**
* Gets the Dew Point Valuation by temperature
* @param {number} temperature Temperature in CELCIUS
* @returns {Array<object>} Dew Point Valuation
*/
function dewPointValuationsByTemperature(temperature) {
if (temperature < 0) {
return DEW_POINT_VALUATIONS.ARDENBUCK_MINUS;
} else if (temperatureC >= 0 && temperatureC <= 50) {
} else if (temperature >= 0 && temperature <= 50) {
return DEW_POINT_VALUATIONS.ARDENBUCK_PLUS;
} else if (temperatureC > 50) {
} else if (temperature > 50) {
return DEW_POINT_VALUATIONS.PAROSCIENTIFIC;
} else {
return DEW_POINT_VALUATIONS.ARDENBUCK_DEFAULT;
}
}

function dewPointMagnusFormula(temperatureSI, humiditySI) {
let T = kelvinToCelcius(temperatureSI);
let RH = humiditySI;
/**
*
* @param {number} temperature Temperature in K (Kelvin)
* @param {number} humidity Humidity in RH (Relative Humidity)
* @returns {number} Dew Point in Kelvin
*/
function dewPointMagnusFormula(temperature, humidity) {
let T = kelvinToCelcius(temperature);
let RH = humidity;
let constants = dewPointValuationsByTemperature(T);

let gammaT_RH = Math.log(RH / 100) + ((constants.b * T) / (constants.c + T));
Expand All @@ -46,9 +44,15 @@ function dewPointMagnusFormula(temperatureSI, humiditySI) {
return celciusToKelvin(Tdp);
}

function dewPointArdenBuckEquation(temperatureSI, humiditySI) {
let T = kelvinToCelcius(temperatureSI);
let RH = humiditySI;
/**
*
* @param {number} temperature Temperature in K (Kelvin)
* @param {number} humidity Humidity in RH (Relative Humidity)
* @returns {number} Dew Point in Kelvin
*/
function dewPointArdenBuckEquation(temperature, humidity) {
let T = kelvinToCelcius(temperature);
let RH = humidity;
let constants = dewPointValuationsByTemperature(T);

let gamma_T_RH = Math.log((RH / 100) * Math.exp((constants.b - (T / constants.d)) * (T / (constants.c + T))));
Expand All @@ -57,30 +61,49 @@ function dewPointArdenBuckEquation(temperatureSI, humiditySI) {
return celciusToKelvin(Tdp);
}

function windChillIndex(temperatureSI, windSpeedSI) {
let v = meterPerSecondToKilometerPerHour(windSpeedSI);
let Ta = kelvinToCelcius(temperatureSI);
/**
*
* @param {number} temperature Temperature in K (Kelvin)
* @param {number} windSpeed Windspeed in M/S (meter per second)
* @returns {number} Wind Chill Index in Kelvin
*/
function windChillIndex(temperature, windSpeed) {
let v = meterPerSecondToKilometerPerHour(windSpeed);
let Ta = kelvinToCelcius(temperature);
let v_exp = (v ** 0.16);

let Twc = 13.12 + (0.6215 * Ta) - (11.37 * v_exp) + (0.3965 * Ta * v_exp);
return celciusToKelvin(Twc);
}

function australianAapparentTemperature(temperatureSI, humiditySI, windSpeedSI) {
let Ta = kelvinToCelcius(temperatureSI);
let v = windSpeedSI;

let e = (humiditySI / 100) * 6.015 * Math.exp((17.27 * Ta) / (237.7 + Ta));
/**
*
* @param {number} temperature Temperature in K (Kelvin)
* @param {number} humidity Humidity in RH (Relative Humidity)
* @param {number} windSpeed Windspeed in M/S (meter per second)
* @returns {number} Apparent Temperature in Kelvin
*/
function australianAapparentTemperature(temperature, humidity, windspeed) {
let Ta = kelvinToCelcius(temperature);
let v = windspeed;

let e = (humidity / 100) * 6.015 * Math.exp((17.27 * Ta) / (237.7 + Ta));
let AT = Ta + (0.33 * e) - (0.7 * v) - 4.00;

return celciusToKelvin(AT);
}

function heatIndex(temperatureSI, humiditySI) {
if (humiditySI > 100 || humiditySI < 0) return null;
/**
*
* @param {number} temperature Temperature in K (Kelvin)
* @param {number} humidity Humidity in RH (Relative Humidity)
* @returns {number} Heat Index in Kelvin
*/
function heatIndex(temperature, humidity) {
if (humidity > 100 || humidity < 0) return null;

let T = kelvinToCelcius(temperatureSI);
let R = humiditySI;
let T = kelvinToCelcius(temperature);
let R = humidity;

let c1 = -8.78469475556;
let c2 = 1.61139411;
Expand All @@ -100,24 +123,33 @@ function heatIndex(temperatureSI, humiditySI) {
return celciusToKelvin(HI);
}

function heatIndexText(heatIndexTemperatureSI) {
/**
*
* @param {number} heatIndexTemperature Temperature in K (Kelvin)
* @returns {string} Heat Index Warning
*/
function heatIndexText(heatIndexTemperature) {
let thresholds = [
{ lowerLimit: 52, text: "Extreme danger", warning: "Heat stroke is imminent." },
{ lowerLimit: 40, text: "Danger", warning: "Heat cramps and heat exhaustion are likely; heat stroke is probable with continued activity." },
{ lowerLimit: 33, text: "Extreme caution", warning: "Heat cramps and heat exhaustion are possible. Continuing activity could result in heat stroke." },
{ lowerLimit: 26, text: "Caution", warning: "Fatigue is possible with prolonged exposure and activity. Continuing activity could result in heat cramps." }
];

let result = thresholds.find((t) => {
return heatIndexTemperatureSI >= (t.lowerLimit + KELVIN);
});
let result = thresholds.find((t) => heatIndexTemperature >= (t.lowerLimit + KELVIN));

return result == null ? "No warning" : result;
}

function humidex(temperatureSI, humiditySI) {
let Tair = kelvinToCelcius(temperatureSI);
let Tdew = dewPointMagnusFormula(temperatureSI, humiditySI);
/**
* Gets the Humidex temperature
* @param {number} temperature Temperature in K (Kelvin)
* @param {number} humidity Humidity in RH (Relative Humidity)
* @returns {number} Humidex in Kelvin
*/
function humidex(temperature, humidity) {
let Tair = kelvinToCelcius(temperature);
let Tdew = dewPointMagnusFormula(temperature, humidity);

let e = 6.11 * Math.exp(5417.7530 * ((1 / 273.16) - (1 / Tdew)));
let h = (0.5555) * (e - 10.0);
Expand All @@ -126,43 +158,70 @@ function humidex(temperatureSI, humiditySI) {
return celciusToKelvin(humidex);
}

function humidexText(humidexSI) {
/**
* Gets the Humidex test warning
* @param {number} humidex Temperature in K (Kelvin)
* @returns {string} Humidex Warning
*/
function humidexText(humidex) {
let thresholds = [
{ lowerLimit: 46, text: "Dangerous" },
{ lowerLimit: 40, text: "Great discomfort" },
{ lowerLimit: 30, text: "Some discomfort" }
];

let result = thresholds.find((t) => {
return humidexSI >= (t.lowerLimit + KELVIN);
});
let result = thresholds.find((t) => humidex >= (t.lowerLimit + KELVIN));

return result == null ? "No warning" : result;
}

function kelvinToCelcius(temperatureSI) {
return temperatureSI - KELVIN;
/**
* Convert Kelvin to Celcius
* @param {number} temperature Temperature in K (Kelvin)
* @returns {number} Celcius
*/
function kelvinToCelcius(temperature) {
return temperature - KELVIN;
}

function celciusToKelvin(temperatureC) {
return roundToTwoDecimals(temperatureC + KELVIN);
/**
* Convert Celcius to Kelvin
* @param {number} temperature Temperature in C (Celcius)
* @returns {number} Kelvin
*/
function celciusToKelvin(temperature) {
return roundToTwoDecimals(temperature + KELVIN);
}

/**
* Round decimal number to two decimals
* @param {number} num Number
* @returns {number} num rounded to two decimals
*/
function roundToTwoDecimals(num) {
return Math.round(num * 100) / 100;
}

function meterPerSecondToKilometerPerHour(meterPerSecond) {
return meterPerSecond * 3.6;
/**
* Convert M/S to KM/H
* @param {number} mps Meter Per Second
* @returns {number} KM/H
*/
function meterPerSecondToKilometerPerHour(mps) {
return mps * 3.6;
}

module.exports = {
dewPointMagnusFormula: dewPointMagnusFormula,
dewPointArdenBuckEquation: dewPointArdenBuckEquation,
windChillIndex: windChillIndex,
australianAapparentTemperature: australianAapparentTemperature,
heatIndex: heatIndex,
heatIndexText: heatIndexText,
humidex: humidex,
humidexText: humidexText
dewPointMagnusFormula,
dewPointArdenBuckEquation,
windChillIndex,
australianAapparentTemperature,
heatIndex,
heatIndexText,
humidex,
humidexText,
roundToTwoDecimals,
kelvinToCelcius,
celciusToKelvin,
meterPerSecondToKilometerPerHour
}

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