New stats and the explanation

Hello what is the meaning or the explanation of those two new values?

`Wet Bulb Temperature

Wet Bulb Globe Temperature`

Wet Bulb Temperature, along with the dry bulb temperature, can be used to determine relative humidity - Wet-Bulb Temperature - an overview | ScienceDirect Topics.

Wet Bulb Globe Temperature (WBGT) is a heat stress index … unlike many heat stress indices it includes a measurement of the effects of direct sunlight (so, if it is cloudy there is less direct sunlight and WBGT would trend lower during cloudy periods … and in the spring, winter and autumn, the lower sun angle also produces a lower WBGT) and wind speed … Wet Bulb Globe Temperature, Latest + Forecasts .

Hi @michaelloercher ,
Thank you for this question :slight_smile:
I had not seen the Wet bulb globe temperature displayed until you asked this question and was keen to find it because it is very useful. I had to search because it is only displayed for my Tempest and is not displayed for my Sky and Air combination, which is why I had never noticed it.

I would like to know the formula being used to calculate the Wet bulb globe temperature because it must include the suns angle therefore will be different depending on the time of day and where on Earth each Tempest is located.
(@eric can you obtain the formula being used?)
The formula could be added to this page:
https://weatherflow.github.io/Tempest/api/derived-metric-formulas.html

Most people assume that the readings for the suns radiation and UV index displayed in the weather reports is what they would feel from the sun. But that is not correct due to the instruments reading the radiation such as the panel on the top of the Tempest is horizontal. But if we are facing the sun when it is near the horizon our face is receiving a stronger amount of radiation than the amount measured on a horizontal surface.

So the Wet bulb globe temperature is a very good (The Best?) indicator of how hot we feel standing in the sun with our body sweating.
cheers Ian :slight_smile:

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well, both the global irradiance and the UV-index require horizontally placed detectors. But you are right, WBGT is a nice indicator for the intensity of the sun, But keep in mind that it doesn’t warn you for UV at all. I’m also curious how that is derived from the measured values.

Interesting enough, I brought the tempest inside to see how WBGT reacted to increase in temperature.
temperature T (series1) vs Wet Bulb Global temperature WBGT (series2) and dewpoint DP (series3) (solar irradiance 0 W/m2, windspeed = 0.0 m/s) at random time samples:

T 11.7 WBGT 14.4
T 13.0 WBGT 15.1 DP 10.0
T 14.0 WBGT 15.6 DP 10.2
T 15.7 WBGT 16.5 DP 10.9
T 16.9 WBGT 17.0 DP 11.2
T 17.6 WBGT 17.5 DP 11.6
T 18.2 WBGT 17.8 DP 12.0
T 18.8 WBGT 18.1 DP 12.1
T 19.4 WBGT 18.4 DP 12.4
T 19.9 WBGT 18.6 DP 12.6
T 21.0 WBGT 19.2 DP 13.2
T 21.5 WBGT 19.5 DP 13.4
T 22.5 WBGT 20.1 DP 13.8
T 23.0 WBGT 20.3 DP 14.0
T 23.5 WBGT 20.5 DP 14.2
T 23.9 WBGT 20.9 DP 14.6
T 24.4 WBGT 21.1 DP 14.8
T 24.8 WBGT 21.2 DP 14.9
T 25.5 WBGT 21.7 DP 15.2
T 26.3 WBGT 22.1 DP 15.7
T 27.3 WBGT 22.7 DP 16.3
T 28.4 WBGT 23.2 DP 16.7

and with a wet towel in the oven as well (which should give a humidity of around 95%) :
T 14.8 WBGT 17.0 DP 13.0
T 15.4 WBGT 17.7 DP 14.1
T 16.1 WBGT 15.3 DP 15.0
T 16.9 WBGT 16.2 DP 15.9
T 17.8 WBGT 17.1 DP 16.8
T 18.7 WBGT 18.0 DP 17.7
T 19.5 WBGT 18.8 DP 18.5
T 20.3 WBGT 21.9 DP 19.5
T 21.0 WBGT 22.5 DP 20.2
T 21.7 WBGT 23.0 DP 20.9
T 22.4 WBGT 23.6 DP 21.6
T 23.0 WBGT 24.1 DP 22.2
T 23.6 WBGT 24.6 DP 22.8
T 24.1 WBGT 25.0 DP 23.2
T 24.6 WBGT 25.4 DP 23.7
T 25.5 WBGT 26.1 DP 24.6
T 26.2 WBGT 26.7 DP 25.3
T 27.2 WBGT 27.5 DP 26.3
T 28.1 WBGT 28.3 DP 27.2

Do I understand these data points. No, not at all… certainly not the sudden drop in values.

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Ok here is the formula used for those loving maths

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interesting but quoted from the article :

The values to be entered are wind speed (u in meters per hour), ambient temperature (Ta
in degrees Celsius), dew point temperature (Td in degrees Celsius), solar irradiance (S in
Watts per meter squared), direct beam radiation from the sun (𝑓𝑑𝑏) and diffuse radiation
from the sun (𝑓𝑑𝑖𝑓).

but we don’t have direct beam radiation, so how to proceed?

At the bottom of the article there is a formula for wet bulb temperature:
Wet Bulb Temperature = (-5.806 + 0.672 * Ta – 0.006 * Ta^2 +(0.061 + 0.004 * Ta + 9910^-6 * Ta^2) * RH + (-3310^-6 – 5*10^-6 *Ta – 1 * 10^-7 * Ta^2) * RH^2)