What does dew point mean?

Answer 1

Every air mass contains some water vapour which is the gaseous form of water. The amount of water vapour in the air varies considerably, coastal areas tend to have more than inland areas.

Water vapour in the air is constantly condensing to form minute water droplets and these droplets are constantly evaporating. The rate of evaporation is governed by the temperature - the hotter it is, the more evaporation. If you cool the air, the rate of evaporation decreases. At a particular temperature, the rate of evaporation equals the rate of condensation. This temperature is the dewpoint. At this temperature, the air is saturated, it is at 100% relative humidity and the vapour pressure is at the saturation vapour pressure.

If the temperature falls further, the condensation exceeds the evaporation and the water vapour condenses into liquid water. This could be dew on the ground, fog close to the ground or cloud above the ground. The air is cooled either by being lifted or by the ground radiating heat into space.

Air does not "hold" water vapour any more than it "holds" oxygen.

Answer 2

The temperature at which the air's relative humidity would be 100% if you did not change anything else than the temperature. Hot air can hold far more humidity than cold air.

If the air cools below the dew point, the humidity contained in the air condenses and forms a stratus cloud (if near the ground = fog).

If a "bubble" of air is moving upwards, its temperature will decrease as the pressure diminishes. If it goes up far enough for its temperature to fall below the dew point of the bubble, then a cloud forms.

If the bubble is climbing rapidly (as on a hot sunny summer day), you get cumulus clouds. If it climbs violently (as when a cold front pushes on a warm front), you get cumulonimbus (storm clouds).

If it rises slowly (as when a warm front pushes on a colder air mass) you get the stratus family.

Answer 3

The dew point is the temperature to which a given parcel of air must be cooled, at constant barometric pressure, for water vapor to condense into water. The condensed water is called dew. The dew point is a saturation point. When the dew point temperature falls below freezing it is often called the frost point, as the water vapor no longer creates dew but instead creates frost or hoarfrost by deposition. The dew point is associated with relative humidity. A high relative humidity indicates that the dew point is closer to the current air temperature. Relative humidity of 100% indicates the dew point is equal to the current temperature and the air is maximally saturated with water. When the dew point remains constant and temperature increases, relative humidity will decrease.[1] At a given barometric pressure, independent of temperature, the dew point indicates the mole fraction of water vapor in the air, and therefore determines the specific humidity of the air. The dew point is an important statistic for general aviation pilots, as it is used to calculate the likelihood of carburetor icing and fog, and estimate the height of the cloud base.

Answer 4

Dew point is the temperature needed to cause water to condense. This temperature depends on the humidity of the air.

Very humid air will begin to condense water at fairly high temperatures so the dew point could be high, like 90 degrees F (we have dew points like that sometimes here in mississippi).

Very dry air must be cooled down quite low before the first drop of water "rains" out, so it has a low dew point.

Again, the dew point is the temperature that is cold enough to make the air start "dewing" or "raining" or "condensing".

Answer 5

Dew point means that the temperature and the saturation of water vapor in the air has reached a point where the air can no longer hold all that vapor and that water will accumulate (in liquid form) on objects. The higher the temperature of the air the more water vapor it can hold. That is why in the morning (typically when the air temperature is at it's lowest) water droplets will form on plants, rocks building, etc.

EDIT: Others explained it better than myself and posted while I was still typing :P

Answer 6

It indicates the temperature at which dew will be created for a given humidity level. In other words, an indicate of humidity.

Answer 7

Dewpoint is the temperature at which air would become saturated if it is cooled sufficiently,a further lowering of this temperature being responsible for spontaneous condensation.
In other words it is the temperature for which the saturation vapour pressure is identical with the actual pressure of the vapour in the air.

Answer 8

Dewpoint = in an easy way to understand. ITs the temp. needed to get rain.

say weather is 40 degrees and dew point is 42. then it needs to be under the dewpoint to rain.

Answer 9

the temperature at which the air is saturated with moisture