https://www.davisinstruments.com/product_documents/weather/app_notes/AN_28-derived-weather-variables.pdf
On Sunday, December 9, 2018 at 8:07:28 PM UTC-5, Philip Kutzenco wrote: > > First, let me apologize for hijacking this Belchertown thread to get > educated on Apparent Temperature. > > Second, thanks Gary, your explanation clarifies it for me. It seems I was > fixed on a simplistic definition of Apparent Temperature sometimes used in > the US which yields the same value as either Wind Chill, Temperature, or > Heat Index depending upon the value of "actual temperature". In contrast, > the weewx calculation relies on the more sophisticated model developed by > Steadman. > > I actually like that the weewx calculated value is different than what I > thought it should be. The simplistic definition doesn't add any new > information as you could just look at Wind Chill, Heat Index and > Temperature to get the same information the simple definition provides. In > addition, I don't actually know what formula Vantage uses to calculate Wind > Chill and Heat Index (I'll look it up), which my station hardware > calculates and provides. > > The Steadman model gives a more nuanced value probably closer to what is > intended - that is, what the human body perceives the temperature to be. > > I'll move any further questions I have on this to a separate topic. > phil > > On Sunday, December 9, 2018 at 6:05:08 PM UTC-5, gjr80 wrote: >> >> As you point out weeWX windchill and heatindex values track outTemp below >> certain minimums and above certain maximums respectively. The weeWX >> calculated appTemp uses the formulas mentioned in the post you linked and >> is quite different to a composite heatindex and windchill (by composite I >> mean windchill below 50F and heatindex above 81F). The key difference >> (other than the formula) is that appTemp is valid across all temperatures. >> appTemp is certainly affected by wind speed (just look at the formula), I >> often notice appTemp moving in time (and quite markedly) with wind speed >> changes on my realtime gauges. >> >> I like to think of 'feels like' as being a term that means different >> things to different people and without an agreed understanding can be a >> source of confusion. It really is just a general term that tries to better >> approximate the effect of current weather conditions on the body, it could >> be based on a measure of heatindex, windchill, humidex, wet bulb globe >> temperature or apparent temperature. For me in Australia I think of >> apparent temperature, I expect in Canada humidex may be a more accepted >> measurement. >> >> The use of the term 'apparent temperature' can also be confusing at >> times; does it refer to the accepted formula for Apparent Temperature (as >> you linked or as used by weeWX) or is it the more literal meaining. For >> this reason I prefer to refer to something like the 'weeWX appTemp field' >> or 'Apparent Temperature' to make it clear I am referring to the calculated >> value. >> >> Gary >> >> -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
