HUMIDITY AND DEW POINT

CONDENSATION � H2O can exist in solid, liquid, or gaseous states. Change from liquid to gas is evaporation. Change from gas to liquid is condensation. � Condensation occurs where the relative humidity 100% (saturation) C E Ppt T When air is saturated, the rate of evaporation equals condensation

DEW POINT The dewpoint is the temperature at which condensation begins to form. Measures the amount of water vapor in the air. In your own words, come up with an example of how to illustrate dewpoint in the natural environment.

Thermoregulation: body sweats and as sweat evaporates, the body is cooled. How would you be affected if the humidity levels were high?

RELATIVE HUMIDITY Humidity is a measure of the amount of water vapor (gas) in the air. Relative humidity is a measure of how much water vapor the air actually could "hold" at a certain temperature. (air is like a sponge) Is written as a percentage Saturated air will have an RH of 100 %. You need the RH of 100% to have rain form in clouds.

To measure relative humidity use a psychrometer Dry bulb thermometer and a wet bulb thermometer mounted together Dry bulb tells actual temperature Wet bulb shows how much water can be evaporated – temperature lowers as water is evaporated

The difference in temperature on the 2 thermometers is an indication of the amount of water vapor in the air.

Wet- and Dry Bulb Psychrometer Psychrometric Chart. If the difference between wet and dry bulb is 6º F and the temperature is 72º F (dry bulb), then the RH is 54%.

How would a psychrometer be affected if the air was moist? How would a psychrometer be affected if the air was dry?

When the Wet bulb temperature = the dry bulb temperature……… 100% HUMIDITY!!!