Weather in this area has a strong impact on human life, so information about the state of the earth’s atmosphere is always useful from an economic point of view and from the point of view of safety for health. Temperature inversion is a type of state of the lower atmosphere. What it is and where it appears is considered in the article.
What is temperature inversion?
By this concept is meant an increase in air temperature with increasing height from the earth's surface. This seemingly harmless definition entails quite serious consequences. The fact is that air can be considered an ideal gas, for which the pressure at a fixed volume is inversely dependent on temperature. Since the temperature increases with increasing temperature inversion, the air pressure decreases and its density decreases.
From the school course of physics, it is known that convection processes that cause vertical mixing in the volume of a fluid substance located in a gravitational field occur if the lower layers are less dense than the upper ones (hot air always rises). Thus, temperature inversion prevents convection in the lower atmosphere.
Normal atmospheric conditions
As a result of numerous observations and measurements, it was found that in the temperate climatic zone of our planet the air temperature decreases by 6.5 ° C for every kilometer of altitude, that is, by 1 ° C with an increase in height of 155 meters. This fact is due to the fact that the heating of the atmosphere occurs not as a result of the passage of sunlight through it (for the visible spectrum of electromagnetic radiation, the air is transparent), but as a result of absorption of reradiated energy in the infrared range from the surface of the earth and water. Therefore, the closer the air layers to the ground, the more they warm up on a sunny day.
In the tropical climate zone, the air cools more slowly with increasing altitude than the indicated figures (approximately 1 ° C per 180 m). This is due to the presence of trade winds in these latitudes, which transfer heat from the equatorial regions to the tropics. In this case, heat flows from the upper layers (1-1.5 km) to the lower ones, which prevents a rapid drop in air temperature with increasing height. In addition, the thickness of the atmosphere in the tropical zone is greater than in the temperate.
Thus, the normal state of the atmospheric layers consists in their cooling with increasing height above sea level. This condition favors the mixing and circulation of air in the vertical direction due to convection processes.
Why can the upper air layers be warmer than the lower ones?
In other words, why is temperature inversion manifested? This happens for the same reason as the existence of normal atmospheric conditions. Earth has a greater value of thermal conductivity than air. This means that at night, when there are no clouds and clouds in the sky, it cools quickly and those atmospheric layers that are in direct contact with the earth's surface also cool. The result is the following picture: a cold surface of the earth, a cold layer of air in the immediate vicinity of it, and a warm atmosphere at a certain height.
What is temperature inversion and where does it occur? This situation often arises in the lowlands, in absolutely any locality and at any latitude in the morning. Lowland is protected from horizontal movements of air masses, that is, from the wind, so the air cooled in it during the night creates a locally stable atmosphere. The phenomenon of temperature inversion can be observed in mountain valleys. In addition to the described process of night cooling, in the mountains its formation is also facilitated by the “sliding” of cold air from the slopes to the plains.
The lifetime of temperature inversion can last from several hours to several days. Normal atmospheric conditions are established as soon as the earth's surface heats up.
What is the danger of the phenomenon under consideration?
The state of the atmosphere in which there is a temperature inversion is stable and windless. This means that if any emissions into the atmosphere or the evaporation of toxic substances occur in a given territory, they do not disappear anywhere, but remain in the air above the area in question. In other words, the phenomenon of temperature inversion in the atmosphere contributes to a multiple increase in the concentration of toxic substances in it, which poses a huge danger to human health.
The described situation often arises over large cities and megacities. For example, cities like Tokyo, New York, Athens, Beijing, Lima, Kuala Lumpur, London, Los Angeles, Bombay, the capital of Chile - Santiago and many other cities around the world often suffer from the effects of temperature inversion. Due to the large concentration of people, industrial emissions in these cities are gigantic, which leads to smog in the air, which impairs visibility and poses a threat not only to health but also to human life.
So, in 1952 in London and in 1962 in the Ruhr Valley (Germany), several thousand people died as a result of the long time of the existence of temperature inversion and significant emissions of sulfur oxides into the atmosphere.
Capital of Peru, Lima
Opening the question of what is temperature inversion in geography, it is interesting to bring the situation in the capital of Peru. It is located on the Pacific Ocean and at the foot of the Andes Mountains. The coast near the city is washed by the cold Humboldt Current, which leads to severe cooling of the earth's surface. The latter, in turn, contributes to the cooling of the lowest air layers and the formation of mists (with decreasing air temperature, the solubility of water vapor in it decreases, the latter manifests itself in the formation of dew and fog).
As a result of the described processes, a paradoxical situation arises: the coast of Lima is covered with fog, which prevents the rays of the sun from heating the earth's surface. Therefore, the state of temperature inversion is so stable (mountains interfere with horizontal air circulation) that it almost never rains here. The latter fact explains why the coast of Lima is almost a desert.
How to behave in case of receiving information about the adverse state of the atmosphere?
If a person lives in a large city and he has received information about the existence of a temperature inversion in the atmosphere, it is recommended not to go outside in the morning, if possible, but to wait until the earth warms up. If such a need arises, then you should use individual respiratory protective equipment (gauze bandage, scarf) and do not stay outdoors for a long time.