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Temperature (and humidity) measurement: Difference between revisions
Temperature (and humidity) measurement (view source)
Revision as of 22:16, 13 June 2020
, 13 June 2020→Cumulus Calculated Parameters: dew point
m (→Cumulus Calculated Parameters: dew point) |
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[http://en.wikipedia.org/wiki/Wet_bulb Wet bulb]
and [https://en.wikipedia.org/wiki/Dew_point Dew point]▼
*The dew point calculation for Cumulus 1 uses a third party library which uses the Davis dew point calculation '''dewpoint := tempinC + ((0.13 * tempinC) + 13.6) * Ln(humidity / 100)''' ▼
* The dew point calculation for MX follows the standard [https://en.wikipedia.org/wiki/Dew_point calculation in wikipedia].
Note this means that Cumulus 1 and MX log files have a continuity break when you migrate from one flavour to another.
<pre>
/* =================================================================================================
DEW POINT TEMPERATURE
The dew point calculation in Cumulus 1 uses a third party library which uses the Davis dew point calculation '''dewpoint := tempinC + ((0.13 * tempinC) + 13.6) * Ln(humidity / 100)'''
============================================================================== */
function calcDewPoint(tempDegC, tempLetter, RHumidity)
{
var dp = tempDegC + ((0.13 * tempDegC) +13.6) * Math.log(RHumidity / 100);
return calcTempR(dp, tempLetter); // return as string in right units for user
}
/* =================================================================================================
DEW POINT TEMPERATURE
The following is a formula from https://github.com/nicolasgrancher/weather-js/blob/master/js/weather.js
This matches the formula that MX uses.
It has only been edited to add the middle input parameter and to output using a call to CalcTempR
============================================================================== */
/**
* Dew point calculation.
*
* @param Tc temperature in celsius
* @param R relative humidity
* @returns {number}
*/
function dewPoint(Tc, tempLetter, R)
{ // parameters: tempDegC, tempLetter, (RHumidity /100) // added middle parameter, should be accessible anyway, but playing safe
if (Tc < 0 || Tc > 60)
{
return calcTempR(Tc, tempLetter); // return as string in right units for user
}
if (R < 0.01 || R > 1) {
return calcTempR(Tc, tempLetter); // return as string in right units for user
}
var a = 17.27;
var b = 237.7;
var alphaTR = ((a * Tc) / (b + Tc)) + Math.log(R);
var Tr = (b * alphaTR) / (a - alphaTR);
if (Tr < 0 || Tr > 50) {
return calcTempR(Tc, tempLetter); // return as string in right units for user
}
return calcTempR(Tr, tempLetter); // return as string in right units for user
}
</pre>
▲ and [[#How_does_Cumulus_know_the_height_of_the_cloud_base.3F]]
▲The dew point calculation uses a third party library which uses the Davis dew point calculation '''dewpoint := tempinC + ((0.13 * tempinC) + 13.6) * Ln(humidity / 100)'''
[[Humidex]] and [[Wind chill]] and [[Heat index]] and [[#My heat index/humidex/wind chill is the same as my temperature]]
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