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Humidex question
Posted: Tue 08 Feb 2011 4:19 am
by fractonimbus
One of the realtime.txt values is "Humidex". Is this what is also plotted in the standard C 1.9.1 web page as "Apparent Temperature"?
fracto
Re: Humidex question
Posted: Tue 08 Feb 2011 8:16 am
by nking
No they are not the same, take a look at FAQ's.
Re: Humidex question
Posted: Tue 08 Feb 2011 9:52 am
by fractonimbus
Yes, thanks, I found an earlier post on the subject,
https://cumulus.hosiene.co.uk/viewtopic.php?f=14&t=3482
I've just coded the apparent temperature for PHP, which as a single equation is as follows:
$apptemp = round(($temp + 0.33*($hum/100)*6.105*exp(17.27*$temp/(237.7+$temp))- 0.70*$wspeed - 4.00),1);
I always use brackets (...) around anything where I don't trust the order of compuation (or don't know the language).
The round(x,1) command trims it back to one decimal place.
Here, $apptemp is the apparent temperature variable, $temp is the (dry bulb) temperature, $hum is the relative humidity, and $wspeed is the average windspeed. Seems to work OK.
fracto