Atmospheric fronts are what? What are they like?

Watching the weather changes is very exciting. The sun is replaced by rain, the rain is snow, and gusty winds blow over all this diversity. In childhood, it causes admiration and surprise, in older people - the desire to understand the mechanism of the process. Let's try to understand what forms the weather and how the atmospheric fronts are related to this.

Air mass boundary

In the usual perception, the "front" is a military term. This is the face on which the collision of enemy forces occurs. And the concept of atmospheric fronts is the boundary of contact between two air masses, which form over vast areas of the Earth's surface.

By the will of nature, man has the opportunity to live, evolve and populate all large areas. The troposphere - the lower part of the Earth's atmosphere - provides us with oxygen and is in continuous motion. It consists of separate air masses, united by a common origin and similar indicators. Among the main indicators of these masses determine the volume, temperature, pressure and humidity. During the movement, different masses can approach and collide. However, they never lose their borders and do not mix with each other. Atmospheric fronts are areas where air masses come in contact and sudden weather jumps occur.

A bit of history

The concepts of "atmospheric front" and "frontal surface" did not arise on their own. They were introduced into meteorology by the Norwegian scientist J. Bjerknes. It happened in 1918. Bjerknes proved that atmospheric fronts are the main links in the atmosphere's circulation in the high and middle layers. However, before the studies of the Norwegian, as early as 1863, Admiral Fitzroy suggested that violent atmospheric processes begin at the meeting places of the masses of air coming from different directions of the world. But at that time the scientific community did not pay attention to these observations.

The Bergen school, represented by Bjerknes, not only conducted its own observations, but also brought together all the knowledge and assumptions made by earlier observers and scientists and presented them in the form of a consistent scientific system.

By definition, the inclined surface, which is the region of transition between different air currents, is called the frontal surface. But the atmospheric fronts are the mapping of frontal surfaces onto a meteorological map. Usually the transition region of the atmospheric front is tied at the surface of the Earth and rises up to the heights at which the differences between the air masses are blurred. Most often the threshold of this height is from 9 to 12 km.

Warm front

Atmospheric fronts are different. They depend on the direction of movement of warm and cold massifs. There are three types of fronts: cold, warm and occlusions, formed at the point of closing of various fronts. Let us consider in more detail what warm and cold atmospheric fronts are.

A warm front is a movement of air masses, in which cold air gives way to warm air. That is, the air of a higher temperature, advancing, is located in a territory dominated by cold air masses. In addition, it rises skyward along the transition zone. At the same time, the air temperature gradually decreases, which causes condensation of the water vapor present in it. So clouds are formed.

The main features on which it is possible to determine a warm atmospheric front are:

• The atmospheric pressure drops sharply;
• The dew point increases;
• The air temperature rises;
• Appear pinnate, then pinnately-layered, and after - high-layered clouds;
• The wind turns slightly to the left and becomes stronger;
• Clouds become layered-rain;
• Precipitations of different intensity fall out.

Usually, after the precipitation stops, it warms, but it does not last long, as the cold front moves very fast and catches up a warm atmospheric front.

Cold front

There is such a feature: the warm front is always inclined towards the movement, and the cold front is in the opposite direction. When the fronts move, cold air is wedged into the warm, pushing it up. Cold atmospheric fronts lead to a decrease in temperature and cooling in a large area. As the warm air masses have cooled, the moisture condenses into cloudiness.

The main features on which you can determine the cold front:

• Front of the front, the pressure drops, it increases sharply beyond the atmospheric front line;
• Cumulus clouds are formed;
• There is a gusty wind, with a sharp change of direction clockwise;
• Begins heavy rain with a thunderstorm or hail, the duration of precipitation is about two hours;
• The temperature drops sharply, sometimes by 10 ° C immediately;
• Numerous clearings are observed behind the atmospheric front.

For travelers to go through the cold front - the test is not easy. Sometimes it is necessary to overcome vortices and squalls in conditions of poor visibility.

Front of Occlusion

It has already been said that atmospheric fronts are different, if everything is clear with warm and cold, then the front of occlusions causes a lot of questions. The formation of similar effects takes place at the places where the cold and warm fronts close. Warmer air is pushed upwards. The main action takes place in the cyclones at a time when a more rapid cold front is catching up warm. As a result, the atmospheric fronts move and three air masses collide, two cold and one warm.

The main signs on which it is possible to determine the front of occlusions:

• Clouds and sediments of the general type;
• Sudden changes in wind direction without a strong change in speed;
• Smooth pressure change;
• Absence of sudden temperature changes;
• Cyclones.

The front of the occlusions depends on the temperature of the cold air masses in front of it and behind its line. There are cold and warm fronts of occlusions. The most difficult conditions are observed at the moment of immediate closure of the fronts. As the warm air is forced out, the front is washed out, weather conditions improve.

Cyclone and anticyclone

Since the concept of "cyclone" was used in describing the front of occlusions, it is necessary to tell what kind of phenomenon it is.

Due to the uneven distribution of air in the surface layers, high and low pressure zones are formed. High-pressure zones are characterized by excessive air, low - insufficient number. As a result of the flow of air between the zones (from excessive to insufficient), a wind is formed. Cyclone is a low-pressure section that tightens, like a funnel, missing air and clouds from areas where they are in excess.

Anticyclone is an area with increased pressure, which displaces excess air into low pressure zones. The main characteristic is clear weather, since clouds from this zone are also being displaced.

Geographical division of atmospheric fronts

Depending on climatic zones over which atmospheric fronts are formed, they are divided by geographic feature into:

1. Arctic, separating the cold arctic air masses from the moderate ones.
2. Polar, located between the temperate and tropical masses.
3. Tropical (trade-wind), delimiting the tropical and equatorial zones.

Influence of the underlying surface

The physical properties of the air masses are affected by radiation and the appearance of the underlying surface of the Earth. Since the nature of such a surface may be different, friction about it also occurs unevenly. A complex geographic relief can deform the atmospheric front line and change its effects. For example, there are cases of destruction of atmospheric fronts when passing through mountain ranges.

The air masses and atmospheric fronts bring many surprises to the weather forecasters. Comparing and studying the directions of mass movement and the vagaries of cyclones (anticyclones), they compose graphs and forecasts that people use every day without even thinking about how much work behind it is worth.