heat insulationAdiabatic cooling refers to that during the adiabatic rise of air, the air pressure decreases with the rise of height, and the air block works due to volume expansion, which leads to the reduction of air temperature.Adiabatic cooling causes water vapor condensation orSublimationThis is the most important process of the formation of many water vapor condensates and condensates in the atmosphere, such as clouds and rain.
Chinese name
Adiabatic cooling
Foreign name
adiabatic cooling
Impact
Formation of water vapor condensate and condensate
Discipline
meteorology
Principle
When the air rises and the air pressure decreases, the air block works and consumes energy
When air rises from the ground, its pressure decreases and its volume expands. If there is no heat exchange between the rising air and its surroundings, the air temperature will decrease due to energy consumption due to expansion. This temperature change is called adiabatic cooling.According to the calculation, for every 100 meters of air rise in the atmosphere, the temperature will decrease by about 1 ℃ due to the adiabatic change.This adiabatic cooling is the most important process that causes water vapor condensation or condensation. Many water vapor condensates and condensates in the atmosphere, such as clouds and rain, are formed from this.
Heat insulation is the process and function of isolating and preventing heat transfer, loss and convection, so that the temperature or heat in a closed area is not affected or cannot be affected by the outside world, and the internal stability or independent changes can be maintained.The function of thermal insulation includes heat preservation and cold preservation.
Adiabatic process(Adiabatic process) refers to the state change process of any gas without heat exchange with the outside world. It refers to the state change of a system without heat exchange or mass exchange with the surrounding environment.Many important phenomena in the atmosphere areAdiabatic changeofFor example, in the lower atmosphere, the temperature usually decreases with height, mainly due to the adiabatic mixing of air.causeWater vaporThe cooling effect of condensation, cloud and rain is mainly due to the temperature drop when the air rises;Sunny and dry weather is usually related to warming and drying caused by air subsidence.The cooling effect of rising air and the warming effect of sinking air are mainly due to theAdiabatic expansionandAdiabatic compressionResults.
If a system subject to warming or cooling effects exchanges heat with its surroundings through radiation and conduction, it is called a diabatic process.
Air cooling
One of the ways to saturate the air is to reduce the amount of water vapor that the air can hold. In the atmosphere, it mainly depends on air cooling.There are three types of air cooling: radial cooling, advection cooling, and adiabatic cooling.
Formation principle
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Adiabatic cooling, from the ground up, the air pressure decreases rapidly for the following reasons:
(1) The gravity of the whole air column of the surface barometer. The air pressure on the higher side only represents the pressure of the upper air column
(2) The air is compressible, so the air density near the ground is very high, and it decreases rapidly upward
It can be seen that if a piece of air rises for some reason, its volume will expand due to the low ambient air pressure.For the convenience of discussion, it is assumed that the gas field will not exchange energy with the outside world during the rising and falling process, which is called the adiabatic process.When the gas block expands due to low external pressure, such resistance to external pressure must work and consume energy.But since there is no heat supply from the outside world, it is only natural to reduce its own temperature.This is the principle of adiabatic cooling.
According to the calculation, before the gas field is unsaturated, the temperature will decrease by about 1 ℃ due to the adiabatic change every 100 meters of air rise.We call itDry adiabatic straightness(dry adiabatic lapserate)。On the contrary, when the gas field drops, the surrounding pressure will rise, so the temperature will also rise. We call it adiabatic warming, that is, the temperature will rise by one degree every 100 meters.
Atmospheric phenomenon
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Cooling, insulation and clouds
For every 100 meters of air rise in the atmosphere, the temperature will decrease by about 1 ℃ due to the adiabatic change.At a certain temperature, the water vapor contained in the air has a certain limit. Reaching this limit is called "saturation". After the temperature decreases, the amount of water vapor that may be contained in the air will decrease.Therefore, the originally unsaturated air may reach saturation due to adiabatic cooling during the ascending movement. After the air reaches saturation, the excess water vapor will attach to the floating condensation core, forming water droplets.When the temperature is below zero degrees Celsius, the excess water vapor will condense into tiny ice crystals.These water droplets and ice crystals gather together and float in the air to become clouds.[1]
Hail clouds are composed of water droplets, ice crystals and snowflakes.It is generally divided into three layers: the lowest layer is composed of water droplets with a temperature above 0 ℃;The intermediate temperature is from 0 ℃ to minus 20 ℃, which is composed of supercooled water drops, ice crystals and snowflakes;The temperature of the top layer is below - 20 ℃, which is basically composed of ice crystals and snowflakes.
Cooling adiabatic and gravity waves
Atmospheric gravity wave is a kind of wave caused by the interference of statically stable atmosphere.Adiabatic cooling occurs when the gas block is disturbed and moves upward from the equilibrium position, and returns to the equilibrium position under the action of gravity.Similarly, adiabatic warming occurs when moving downward, and buoyancy makes it return to the equilibrium position.The wave formed by the outward propagation of such vibration is called gravity wave because the restoring force is gravity and buoyancy. If the influence of Coriolis force is considered, it is called inertial gravity wave.Gravity waves can act as a trigger mechanism in the occurrence and development of mesoscale convective weather, such as rainstorm, and can also play the role of transmitting energy and momentum.[2]
Difference from adiabatic heating
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The state change of the vertically moving air block in the atmosphere is usually close toheat insulationProcess.
When the air block rises, due to the gradual decrease of the external pressure, the volume of the air block expands and works externally. Under the adiabatic condition, the energy required for work can only be borne by its own energy. Internal energy is consumed and the temperature of the air block drops. This phenomenon of temperature falling due to the rise of the air block adiabatic is called "adiabatic cooling";
When the air block descends, due to the increase of the external pressure, the outside world does work on the air block. Under the adiabatic condition, the work done can only be used to increase the internal energy of the air block, so the temperature of the air block rises. This phenomenon is called“Adiabatic heating”。
