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Night time cooling

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Furqan Ahmed
Furqan Ahmed

Radiation inversions occur at night when the ground and air lose more heat through infrared radiation than they receive from the sun. This causes the air closest to the ground to cool more than the air above, forming an inversion layer. Ideal conditions for strong radiation inversions are calm winds, long nights, dry air, and clear skies. They commonly result in below-freezing temperatures near the ground and temperatures 5属C warmer just a few meters above. The coldest temperatures are usually observed at sunrise as cold air settles into low-lying areas overnight.

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NIGHTTIME COOLING As the sun lowers, its energy is spread over a larger area In late afternoon or early evening, the earths surface and air above begin to lose more energy than they receive The ground and air above cool by radiating infrared energy, a process called radiational cooling The land is much better radiator than air Surface air transfers some energy to the ground by conduction The measured increase in air temperature just above the ground which is formed mainly through radiational cooling of the surface is known as a radiation inversion As radiation inversions occur on most clear, calm nights, they are also called nocturnal inversions
Night time cooling
Radiation Inversions A strong radiation inversion occurs when the air near the ground is much colder than the air higher up Ideal conditions for a strong inversion; calm air long night fairly dry air and cloud-free sky Windless night Long night Clear sky and dry air
Night time cooling
On winter nights in middle latitudes, it is common to experience below-freezing temperatures near the ground and air 5属C warmer at your waist Top of the inversion is usually not more than 100 m above the ground A surface that is wet or covered with vegetation can add water vapor to the air Lowest temperature on any given day is usually observed around sunrise Cold, heavy surface air slowly drains downhill during the night and eventually settles in low-lying basins and valleys
Night time cooling
Night time cooling

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Night time cooling

  • 1. NIGHTTIME COOLING As the sun lowers, its energy is spread over a larger area In late afternoon or early evening, the earths surface and air above begin to lose more energy than they receive The ground and air above cool by radiating infrared energy, a process called radiational cooling The land is much better radiator than air Surface air transfers some energy to the ground by conduction The measured increase in air temperature just above the ground which is formed mainly through radiational cooling of the surface is known as a radiation inversion As radiation inversions occur on most clear, calm nights, they are also called nocturnal inversions
  • 3. Radiation Inversions A strong radiation inversion occurs when the air near the ground is much colder than the air higher up Ideal conditions for a strong inversion; calm air long night fairly dry air and cloud-free sky Windless night Long night Clear sky and dry air
  • 5. On winter nights in middle latitudes, it is common to experience below-freezing temperatures near the ground and air 5属C warmer at your waist Top of the inversion is usually not more than 100 m above the ground A surface that is wet or covered with vegetation can add water vapor to the air Lowest temperature on any given day is usually observed around sunrise Cold, heavy surface air slowly drains downhill during the night and eventually settles in low-lying basins and valleys