Differences between Heat Index, Dew Point and Wet Bulb Temperature

[hmmy]

What are the differences between them? I have not understood well. I know all of them depend on air temperature and relative humidity. If so, why we need to know and the three ones? Only one is not enough? Can someone explain to me which of them is better of our skin's feeling, during summer or winter? Thank you.

Are you ready for the future?

 

[IRstuff]

They're not that related, i.e., the heat index tells you very little about the absolute air temperature and is empirically generated:

http://en.wikipedia.org/wiki/Heat_index#Formula

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[dgillette]

Dry bulb is the plain old air temperature. Below that is the wet bulb temp, which is the lowest that can be achieved by evaporative cooling. Lowest of the three is the dew point, which is the highest temperature of an object on which water vapor will condense; it is simply a measure of the amount of water vapor in the air, and it is independent of air temperature. (Actually, if the air temp is below the dew point, it's raining, snowing, or depositing frost or dew on the grass.) The difference between the dry-bulb temp and the wet-bulb temp indicates the relative humidity; the closer they are, the higher the humidity. You can probably find the charts on the internet somewhere.

Just out of curiosity, why did you ask this question here, of all places?

 

[Ron]

Google psychrometric chart and you'll find loads of charts as dgillette mentioned. The heat index is the temperature that the body perceives and is usually a few degrees above the actual temperature (dry bulb), based on the relative humidity as measured by the relationship between wet bulb temperature and dry bulb temperature as determined from the psychrometric graph/chart.

 

[charnott]

heat index can also refer to lcoal or regional index relationships. in the middle east we have a index chart of temp vs humidity, index values from this chart above 54 mean work in direct sunlight has to cease, above 48 there are specific requirements for rest periods and fluid intakes etc.