Talk:Humidex

Calculation error
The article says "If the temperature remains 30 °C and the dew point rises to 25 °C (77 °F), the humidex rises to 41." According to the formula given in the article, I get a humidex of 42.3 for temperature 30 and dew point 25. 209.195.80.67 17:41, 12 July 2007 (UTC)
 * I came to this talk page for this exact reason. I was going to ask for verification but this comment answers my question. My calculations also give me 42.3 (42.33841). I will update the temperature in the article, rounded to 42.
 * Lanouette (talk) 12:43, 2 February 2010 (UTC)

Removed word 'measurement'
As the humidex is not measured, it is not a measurement. Although it is calculated with an equation, this also does not make it a measurement.99.229.115.25 (talk) 05:16, 19 August 2009 (UTC)

Dimensionless?
The article says "note that humidex is a dimensionless number, but that the number indicates an approximate temperature in °C" -- given the formula, I don't see how it can be dimensionless. It's (air temperature) plus something else ... and air temperature is in units of temperature. That constant of 0.5555 out front of the second term in the formula must have units of °C, to make the whole thing come out in units of °C, right? Ratios can be dimensionless, but when you add something to a term that already has units, the result can't be free of units.


 * One suspects that 0.5555 is the conversion from °F to °C, i.e. "F-humidex" = T + e - 10 if T is in °F. Note that e is the partial pressure of water vapour in millibars. (The saturation pressure equals 10 mbar at 7°C, so e - 10 is positive if the dew point is above 7°C.) You can't add degrees and millibars, but you can add dimensionless numbers equal to "the temperature in degrees" and "the pressure in millibars", just as you could on a calculator. Of course, any physical argument for the formula is going to produce something dimensionally consistent, like T + c*(e - f), where f is also in millibars and c is in degrees per millibar. The fact that c is taken to be unity (with °F) suggests such a physical argument may be lacking, and so the equation is just a "rule of thumb" and the humidex not really a temperature.


 * Would it be better to refer the humidex as unitless, or say: "note that the humidex does not have associated units, but that indicates... "


 * to me, the arguments above mean that it might be a poor model of the perceived temperature (compared to https://en.wikipedia.org/wiki/Wet-bulb_globe_temperature, for instance), but not that the unit is not a temperature. And anyway, adding a unit term to an adimensional one wouldn't be "unitless", it would be inconsistant. If this index is consistant, since it sum a temperature, it must have temperature unit. Whatever poor or uncomplete the underlying model might be. — Preceding unsigned comment added by 2A01:E35:2E4B:8E70:F4FF:5B3:DB9:31A3 (talk) 19:10, 24 June 2019 (UTC)

Add Chart or Table of Values?
Complete well written article. Could benefit from adding a calculated reference chart or table of Humidex values, similar to the one in the (US) Heat Index article. HalFonts (talk) 11:11, 22 June 2012 (UTC)

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