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Under normal conditions, air temperature decreases with increasing altitude. However, under certain weather conditions, for example, during a long period of anticyclonal weather, the opposite situation is observed, and the temperature rises with the increasing altitude. Thus, the colder surface air cannot rise upwards and pollution accumulates near the surface of the earth.
There is also such a phenomenon as isothermy, when the air temperature remains unchanged with increasing altitude. Like inversion, isothermy prevents the dispersion of pollutants in the atmosphere.
Temperature inversion and isothermy are usually destroyed by sunlight. Thus, these meteorological phenomena usually occur after sunset and disappear with sunrise. According to the measurement data, up to 90% of temperature inversions in Moscow occur at night.
The temperature inversion is illustrated by the example of smoke rising from a fire. Smoke will rise vertically, and then, when it reaches the “inversion layer”, it will bend horizontally.
An example of an inversion on a graph on our website.
The color shows the temperature: in blue tones, colder air is displayed, in red tones, warmer. By the color difference, you can tell the difference in temperature. Horizontal scale – time is displayed, vertical scale – height. Thus, if it is seen that below the color is red, and above it is blue, then the temperature decreases with height and there is no inversion. And if a blue color is displayed at the bottom, and red at the top, then the presence of an inversion is clearly shown.
As can be seen from the graph, from 20:00 to 08:00 the next day, there is a layer of warmer air above the surface layer of cold air at heights from 50 to 600 meters. During this period, the intensity of the inversion changed, which can be seen from the change in the color gradient of the graph.
To detect the temperature inversion, Mosecomonitoring uses MTP-5 meteorological temperature profilers, which allow obtaining data on air temperature at various altitudes.
MTP 5 is a tool for remote sensing of the atmosphere, which measures radiation in the atmospheric boundary layer at altitudes from 0 to 1000 meters. The device has unique characteristics, including all-weather operation, a self-calibration system, the possibility of continuous operation, and also has an intuitive software interface.
The atmosphere is a powerful source of radiation, but since temperature changes are insignificant, a very sensitive receiver must be used to record these changes. The heart of the MTR-5 are unique radiometers, as well as an antenna system of a special design, tuned to work in the range of 5 mm.
Atmospheric radiation is measured by scanning it at various angles from the horizon to the zenith. The software restores the measured values to temperature profiles. Data is saved and displayed every 5 minutes at intervals of 50m
Currently, one profiler is located on the territory of the Ostankino television technical center, the second in the Kosino-Ukhtomsky region (in the East of Moscow).