What Is A Bulb Temperature?

[Backtrack]

I always here people talking about a wet/dry bulb temperature.

One question

What are they?

[MAF]

a brief explanation of wet bulb from BBC

The best hygrometer is one which has two thermometers - one of which has its bulb wetted continuously by a wet cloth. This is called a Mason's or a 'wet-and dry-bulb' hygrometer. Air passing over this wet bulb evaporates some water and lowers the wet bulb temperature by an amount that depends on the humidity of the air. To demonstrate this cooling, wet your finger and blow in it. The humidity can be found by noting the difference in temperature between the wet and dry bulb and looking up the RH value in a set of tables. The relative humidity (RH value) is the amount as a percentage of that required to saturate the air completely.

[johnholmes]

or this from the Australian Met office Glossary

Wet-bulb temperature is measured using a standard mercury-in-glass thermometer, with the thermometer bulb wrapped in muslin, which is kept wet. The evaporation of water from the thermometer has a cooling effect, so the temperature indicated by the wet bulb thermometer is less than the temperature indicated by a dry-bulb (normal, unmodified) thermometer. The rate of evaporation from the wet-bulb thermometer depends on the humidity of the air - evaporation is slower when the air is already full of water vapour. For this reason, the difference in the temperatures indicated by the two thermometers gives a measure of atmospheric humidity.

The dry bulb is simply a mercury in glass (if using mercury in glass) with no muslin cover on it, in what is called a Stevenson screen, that measures the actual temperature of the air. In a screen to protect from direct radiation with louvred sides to ensure a free flow of air over both thermometers.

[Backtrack]

Thank you guys!

[chrisbell-nottheweatherman]

I was also unclear on this, so thanks from me!

[Nights King]

Is there a simple equation to calculate wet bulb temperature using temperature and humidity and dew points ect?

Or do i have to put a damp cloth on an old fashioned murcury thermometer?

[johnholmes]

what temperature and humidity data do you collect?

[Nights King]

I have a oregon advanced weather station WMR928

I dont remember seeing wet bulb temp on it? I am at work so cannot check at moment.

[johnholmes]

no most auto weather stations have some kind of humidity sensor rather than the old style dry and wet thermometer in a Stevenson screen as original met stations had. One then used a slide rule to work out relative humidity, vapour pressure and thence the dewpoint.

Wet bulb temperature is thus not needed for most amateur needs.

To get an idea on how to work out the wet bulb-quite useful for more detail weather information-try Google I'm sure there is plenty of info out there. if you don't find it then ask again and I'll go through it.