What is dewpoint?

Question

What is dewpoint and what is humidity? The weatherman says in our area the temp is 87 degrees F. and the humidity is 55% and the dewpoint is 73 degrees. All I know is it is hard to breathe outside. Ick..

Answer 1

The dewpoint is the temperature that you'd have to cool the air down to so that water vapor would start condensing out of it. The higher the dewpoint the more moist the air is. Dewpoints above 65 start getting uncomfortable, and once they get over 75 there is a serious danger of heat stroke if the temperature is also high. People often talke about "90 degrees and 90% humidity," but that is very rare, because it requires a dewpoint of 86 degrees! I might add that the relative humidity is not measured relative to the maximum amount of water vapor that the air can hold, but is relative to the saturation water vapor. Relative humidities greater than 100% can and do exist.

Answer 2

The dewpoint is the point at which moisture in the air condenses if the air is cooled continually. Usually fog or rain occurs at this point.

If the dewpoint reaches the upper teens or lower twenties, it starts to get uncomfortably hot and humid, such as it did in Calgary last week. Calgary has a dry climate, and rarely sees dewpoints above the mid-teens. In Canada, the dewpoint can reach the upper twenties in southern SK, MB, and ON. The highest dewpoints in the 30's would occur in the humid tropics.

Answer 3

Dewpoint is the temperature at which the air becomes saturated with water vapor...i.e., 100% relative humidity.

Relative humidity if the amount of water vapor in the air compared to the maximum amount of water vapor the air at that temperature can hold. So at 87 deg the air is holding 55% of the maximum water vapor that it can hold. If you cooled the air to 73 degrees, the air would be saturated (the humidity would be 100%) and dew would collect on the windows, cars, etc. That's the dewpoint.

Answer 4

Dew point is the temperature at which air would become saturated, if it were cooled sufficiently.If you lower the air temperature below the dew point, spontaneous condensation of water vapour will occur.Clouds form like this only.The maximum amount of water vapour air can contain, varies with temperature.If, at a particular temperature the air contains the maximum moisture, then the air temperature and the dew point temprerature will be the same and the air is said to be saurated.Here the humidity will be 100 percent.If the humidity is less than 100 percent ,Dew point temperature will be less than Air temperature.At 100 percent, both are same.
Relative humidity is the ratio of the amount of water vapour present in the air,to the amount of water vapour required to saturate it at that particular temperature.This is expressed in percentage.In other words Relative humidity is the degree of saturation.

Answer 5

The "dew point" or "dewpoint" of a given parcel of air is the temperature to which the parcel must be cooled, at constant barometric pressure, for water vapor to condense into water, called dew. When the dew point temperature falls below freezing it is called the frost point as the water vapor no longer creates dew but instead creates frost or hoarfrost by deposition. The graph to the right shows the maximum percentage of water vapor that can exist in air at sea level across a range of temperatures. Note that with higher temperatures the equilibrium partial pressure of water vapor increases thus more water evaporates. The behavior of water vapor does not depend on the presence of air. The formation of dew would occur at the dew point even if the only gas present were water vapor. Dew point is a monotonic function of the partial pressure of water vapor, so dew point can be determined from partial pressure of water vapor alone, and vice versa.

Answer 6

*point occurs when all factors converge to create a particular condition. In Dewpoint it is when certain humidity and a certain temperature meet to create Dewey from Malcolm in the Middle. He usually appears in the morning but can appear anytime the conditions exist for him to come around.