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submitted 3 months ago by fossilesque@mander.xyz to c/science_memes@mander.xyz

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[-] alcoholicorn@lemmy.ml 12 points 3 months ago* (last edited 3 months ago)

100F was defined as the human body temperature (The guy they used had a cold or something so it's off by a degree and a half.)

That's useful for perception of heat. When the dry bulb gets above 100F, wind only cools you down by sweat evaporation, and when the wet bulb gets above 100F, even that can’t cool you down, and you will die if you don’t get to a cooler or drier environment.

This is more intuitive than 36.5C.

[-] lime@feddit.nu 13 points 3 months ago* (last edited 3 months ago)

what Fahrenheit used for his endpoints was 1) the melting point of a brine mixture that he didn't write down the ratio of, and 2) his wife's armpit.

those "bulb" things is something i only ever hear of from americans. it's never used here.

and I fail to see how two numbers are somehow differently intuitive. they are just numbers. also, 36.5 is too low. it's pretty much 37.0 now, because average body temp has interestingly enough shifted since he took those measurements.

[-] Voyajer@lemmy.world 6 points 3 months ago

What does Europe use for apparent temperature measurement then? Just humidity and not evaporation?

[-] lime@feddit.nu 3 points 3 months ago

temperature, wind speed and direction, and humidity are given separately. regular news report style forecasts don't give humidity at all.

[-] Venat0r@lemmy.world 1 points 3 months ago

What's a dry/wet bulb?

[-] Voyajer@lemmy.world 5 points 3 months ago

Dry bulb is a normal temperature reading with say a thermometer. Wet bulb is that same thermometer but it is wrapped in a wet cloth to simulate evaporation of sweat.

The purpose of wet bulb temperature measurement is to fix the dangerous temperature threshold at body temperature instead of having to adjust for humidity. So if the wet bulb temperature crosses 35C/95F you know that it is dangerous to even be outside because your sweat can't even evaporate enough to prevent you from overheating just standing in the shade.

[-] alcoholicorn@lemmy.ml 4 points 3 months ago* (last edited 3 months ago)

Dry bulb is the temperature independent of humidity. Wet bulb is has a wet cloth on the thermometer bulb. This simulates how much sweat cools you in the current humidity and wind.

Measuring humidity instead and cross-referencing to get heat index is more common these days, but IMO it's worse. 120 in the desert vs 120 heat index due to humidity is the difference between someone using a hair dryer on your face and getting cooked in a steam room, and it doesn't consider wind and cloud cover.