Dew point depression
Encyclopedia
The dew point depression (T-Td) is the difference between the temperature
and dew point
temperature at a certain height in the atmosphere
.
The smaller the difference, the more moisture
there is, and the higher the relative humidity
. In the lower troposphere
, more moisture (small dew point depression) results in lower cloud base
s and is also important to severe thunderstorm
s. Conversely, instability is increased when there is a mid-level dry layer (large dew point depression) known as a "dry punch", which is favorable for convection
if the lower layer is buoyant.
As it measures moisture content in the atmosphere, the dew point depression is also an important indicator in agricultural and forest meteorology, particularly in predicting wildfire
s.
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
and dew point
Dew point
The dew point is the temperature to which a given parcel of humid air must be cooled, at constant barometric pressure, for water vapor to condense into liquid water. The condensed water is called dew when it forms on a solid surface. The dew point is a saturation temperature.The dew point is...
temperature at a certain height in the atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
.
The smaller the difference, the more moisture
Moisture
Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...
there is, and the higher the relative humidity
Relative humidity
Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions...
. In the lower troposphere
Troposphere
The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....
, more moisture (small dew point depression) results in lower cloud base
Cloud base
This article refers to meteorology. For the airborne base of the TV series Captain Scarlet and the Mysterons, see Cloudbase.The cloud base is the lowest altitude of the visible portion of the cloud...
s and is also important to severe thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
s. Conversely, instability is increased when there is a mid-level dry layer (large dew point depression) known as a "dry punch", which is favorable for convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
if the lower layer is buoyant.
As it measures moisture content in the atmosphere, the dew point depression is also an important indicator in agricultural and forest meteorology, particularly in predicting wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
s.
See also
- Wet-bulb depression
- Atmospheric thermodynamicsAtmospheric thermodynamicsAtmospheric thermodynamics is the study of heat to work transformations in the earth’s atmospheric system in relation to weather or climate...