Trixology
WeatherCat => WeatherCat General Discussion => Topic started by: UncleBuck on December 12, 2012, 02:49:52 AM
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Just wondering....
Is the Heat Index in WC calculated?
If so, is it done the same way that it is done in Aus as shown below from the BoM site:
About the formula for the apparent temperature
The formula for the AT used by the Bureau of Meteorology is an approximations of the value provided by a mathematical model of heat balance in the human body. It can include the effects of temperature, humidity, wind-speed and radiation. Two forms are given, one including radiation and one without. On this site we use the non-radiation version.
Version including the effects of temperature, humidity, and wind:
AT = Ta + 0.33?e − 0.70?ws − 4.00
Version including the effects of temperature, humidity, wind, and radiation:
AT = Ta + 0.348?e − 0.70?ws + 0.70?Q/(ws + 10) − 4.25
where:
Ta= Dry bulb temperature (?C)
e= Water vapour pressure (hPa) [humidity]
ws= Wind speed (m/s) at an elevation of 10 meters
Q= Net radiation absorbed per unit area of body surface (w/m2)
The vapour pressure can be calculated from the temperature and relative humidity using the equation:
e = rh / 100 ? 6.105 ? exp ( 17.27 ? Ta / ( 237.7 + Ta ) )
where:
rh= Relative Humidity [%]
Source: Norms of apparent temperature in Australia, Aust. Met. Mag., 1994, Vol 43, 1-16
Col.
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It's the American calculation. I don't think it would be too difficult to make it selectable though, so I've added it as a feature request for a future release. Many thanks for the suggestion.
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Thanks for that.... I appreciate you looking after us down-unders as we often get forgotten when it comes to internationalisation in software.
Col.
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I have been thinking a bit more about this and this is what I would like to see it work like....
In Aus we use AT (Apparent Temperature) by using the formula I previously quoted. What would be really cool would be to be able to graph the AT so that if it is higher than the current temp it would appear red (i.e. hotter) and if it is below the current temp it would appear blue (i.e. colder) and if it is the same, it appears the same colour as the Temp.
This would then allow me to only have to show two lines on a graph (Temp. and Apparent Temp.) whereas at the moment I have to show three (Temp., Heat Index and Wind Chill).
The attached image shows how I have it currently set up and as you can see when the Temp. Heat Index and Wind Chill are equal, it looks a bit crowded.
Col.
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Thanks for the suggestion - I've added it to the features request list [tup]