How is fog formed? Where does it come from? Gradual formation of fog in the atmosphere.

Natural phenomena are often more admired than man-made ones. No matter what a person does, everyone will look at mountains, hurricanes and tsunamis with admiration. Admiration, horror and awe. All this is natural in relation to such majestic and hazardous phenomena. Interest can also be aroused by more mundane moments; many would not mind learning how fog is formed and whether this natural phenomenon should be feared.

Fight against nature

Man fights with nature throughout his entire existence. Civilization opposes itself to chaotic primordial power:

• People tend to love orderliness and consistency.
• Since primitive times, it was nature, in all its manifestations, that most “spoiled life” for man.
• By struggling with the environment, the first settlers colonized new lands and asserted their power.
• Every year farmers entered into a deadly race with nature. Its meaning was to get as much harvest as possible in a short time and feed everyone who needs it.
• Even in ancient times, doctors were faced with the problems of mass epidemics. Their sources were microorganisms, the same elements of living nature.

Today, although people have become quite distant from nature, having conquered it in many areas through their activities, humanity still largely depends on it. And it cannot be said that no “sudden turn” performed by Mother Nature will be able to erase our civilization and any memories of it.

Where does the fog come from?

The fog, oddly enough, fog comes from the air. To do this, depending on the area, you will need:

• Availability large quantity industrial enterprises and road transport.
• Special weather conditions.
• Reservoirs, preferably rivers and lakes.

Fog caused by the influence of exhaust gases and emissions from factories is usually called smog, and it is typical for industrial centers. If about 150 years ago it was most often found in England, today the “palm” has moved to South America and China. It just so happens that Europe and the USA are trying to move their production as far as possible so as not to “enjoy” the smog and other possible consequences.

Weather changes and the presence of bodies of water affect the amount of evaporated moisture, which leads to the formation of fog. This variety is less dangerous for people, it practically does not cause exacerbation chronic bronchitis and new attacks of bronchial asthma. But visibility is still reduced.

Such fog spreads over the surface and disappears within a few hours. But exceptions are possible; nature does not have many strict rules.

How does fog appear?

To understand the formation of fog, you need to remember movement of air masses:

1. Air moves not only horizontally, but also vertically.
2. There are two types of masses - cold and heated air.
3. Obeying the laws of physics, warm air rises higher, and cold air, on the contrary, descends closer to the surface.
4. During such movement, condensation occurs - evaporation and fixation of microscopic droplets of water in the air.
5. They are best fixed on dust particles, so industrial areas even ordinary fog occurs earlier. What can we say about smog?

Enormous volumes of air are constantly moving, the laws of physics also apply without change. But fog is a rare phenomenon, sometimes forgotten about for months. And the secret is simple, For maximum effect the maximum level of humidity will be required. In dry climates, such phenomena occur only under very low temperatures, extremely low.

So Any fog is based on the movement of warm and cold air , contact and a kind of “conflict” of these two environments, ending with the evaporation of moisture into the environment.

How to make fog at home?

Fog can also be created artificially. The only question is the scale and goals:

At home you will need:

• An empty bottle, preferably a liter bottle. One third filled with hot water.
• A drop of vodka to add to the water.
• Ice tongs and, in fact, a piece of ice. It will need to be kept close to the neck.

That's the whole simple scheme. Of course, you won’t be able to achieve a thick and long fog, but even this result will surprise your guests. For the same purposes, you can acquire a special machine that, based on the same principles, will produce fog on an industrial scale. But this is an expensive option and bulky equipment. For those who are not looking for easy ways.

Formation of fog in stages

There is nothing secret about the formation of fog; physicists revealed the secret of this natural phenomenon centuries ago. This is how fog forms in the atmosphere:

1. There is constant air circulation in the atmosphere.
2. Warm and cold masses move, replacing each other.
3. During movement, condensation and evaporation of moisture occurs.
4. Water can also evaporate from the surface water sources, if the ambient temperature is slightly lower than the water temperature.
5. Droplets are fixed on any surface and linger in the air for some time.
6. The delay is observed for several hours, as a rule. At this time, the surface is covered with a light haze and visibility is significantly reduced.

Fog can be a challenge for those suffering from chronic lung disease. Most often, problems arise with smog. Reduced visibility increases the risk of accidents, so motorists need to either be extremely careful or limit their time behind the wheel of a vehicle for a couple of hours.

Fogs occur at any time of the year, but most often they occur in late summer or autumn, when the air cools faster than the ground cools. As a result, cool air falls to the ground or water, which still retains heat, condensation occurs, and many water droplets hang in the air. It looks like a huge cloud is hanging right above the ground or a body of water. In the place where the fog formed, the air humidity is 100%. Fogs have different structures. If the air temperature is not very cold, above 10 degrees below zero, then the foggy cloud consists of water droplets. At a temperature of 10-15 degrees below zero, the cloud consists of a mixture of water droplets with ice crystals. If the temperature drops below 15 degrees below zero, then ice fog forms when the entire cloud consists of ice crystals. In cities and populated areas fogs are denser due to the fact that condensation mixes with exhaust gases and dust.

What kind of fogs are there?

Fogs are different. It depends on how good the visibility is in the foggy area.

Haze is the weakest type of fog.

Ground fog is fog that spreads over the ground or body of water in a thin layer. This fog has no effect great influence for visibility.

Translucent fog, visibility in which ranges from several tens to several hundred meters. Through such fog the sun and clouds are visible.

Continuous fog, when a whitish cloud envelops the earth, through which it is impossible to see literally anything at a distance of several meters, and sometimes even at arm's length. With such fog, traffic becomes impossible. If a driver finds himself in a cloud of continuous fog, it is better for him to wait until the fog clears.

There are not only natural fogs, but also artificial ones. Artificial fogs arise from industrial activity person. Artificial fog consists of dust, smoke, exhaust gases, chemical substances, other combustion products. Otherwise it is called smog. Smog-one of the most important problems modern cities, as it causes irreparable harm to human health and pollutes the environment.

Finding yourself in the middle of a continuous white cloud, so dense that it is practically impossible to distinguish anything at arm's length, you often ask yourself the question: why such a thick fog formed, why did it white and you begin to wonder how long this phenomenon usually lasts, and also why any fog dissipates.

Fogs are formed when drops or ice crystals accumulate in the air in the lower layers of the atmosphere, causing along earth's surface a cloud-like veil is formed, limiting visibility so much that space beyond one kilometer is not visible, and in some cases objects become difficult to distinguish even at a distance of several meters.

If the temperature environment exceeds -10°C, the vapor veil consists only of droplets. If the temperature fluctuates from -10 to -15°C, it is made up of water droplets and ice crystals, and when it is -15°C outside, the fog consists of small ice crystals, shimmering in the light of night lamps.

Why this phenomenon occurs is not difficult to answer: its appearance is due either to the evaporation of water from a warm surface into cold air, or to the cooling of warm air currents saturated with moisture. For example, the appearance of ground clouds can often be observed in the evening or in the morning after the temperature of the soil and vegetation (grass) drops; the lower layers of the atmosphere cool so much that they begin to release excess moisture in the form of water droplets.

Another example, this time in winter, is fog over a river, lake or other body of water, on the ice of which an ice hole has formed: in cold weather there is always a veil over it, spreading over the water surface. This happens because the temperature of the water during frost is warmer than the ice surrounding it and the air in contact with it (because of this, the air above the water is always warmer than the rest and there is almost always fog over the river in the area of ​​the ice hole).

After warm air mixes with cold air currents, it begins to cool, releasing steam and forming a cloud at the very surface of the Earth. Therefore, the fog over the river and other bodies of water is usually stable and long-lasting: cold and warm air currents and currents constantly mix here.

A striking example of this phenomenon is the Canadian island of Newfoundland located in the Atlantic Ocean. Due to the fact that two currents collide with each other here – the warm Gulf Stream and the cold Labrador Stream, local residents are forced to spend about one hundred and twenty foggy days a year among the haze.

Formation of terrestrial clouds

When air saturated with water vapor cools or mixes with colder air currents, droplets begin to be released into the atmosphere. After this, if there are tiny particles of dust above the earth’s surface, they begin to stick to them, layering on each other and forming drops of more large sizes(the more dust in the air, the faster the cloud forms, so large cities are almost always shrouded in a weak, almost imperceptible veil).

In the warm season, the size of such a drop ranges from 5 to 15 microns, during frosts - from 2 to 5 microns, so winter cold fog is not as thick as summer fog. As soon as the drops reach the required volumes, objects turn out to be blurry and difficult to distinguish: air at heavy fog acquires a whitish tint and bluish when weak.

The answer to the question of why this phenomenon comes in different colors is simple: smaller droplets scatter short blue rays better, while in dense ground clouds larger droplets and light waves scatter all rays equally, regardless of their length.

The water content of such clouds usually does not exceed 0.5 g/m3, but sometimes dense fog can contain up to 1.5 g/m3 (this water is enough for plants to receive the necessary moisture, this is especially important for vegetation in the arid regions of the planet). How impenetrable the shroud will be depends largely on the humidity of the air, which is usually between 85 and 100% during the occurrence of ground clouds:

• if visibility does not exceed 50 meters, thick fog is observed, and the number of drops is 1200 per cubic centimeter;
• if the space is visible at a distance of 50 to 500 meters - moderate (water drops in this case from 100 to 600);
• if visibility is a kilometer - weak (drops - from 50 to 100).

Fogs are also common during frosts, and the phenomenon can be seen even when the humidity does not exceed fifty percent. They can usually be observed in cities, especially at railway and bus stations, where the haze is formed by steam that appears during the combustion of fuel and is released into the air through chimneys and exhaust pipes.

Kinds

Terrestrial clouds do not always owe their origin only to nature: a large number of fogs occur in cities, and therefore they consist not only of drops and dust, but also smoke, soot, which are emitted by factory or chimneys, or arise after or during fires, when a forest, peat or steppe burns. Based on their origin, meteorologists divide fogs into dry (smoke, soot, etc. are to blame for their formation) and wet (only water and dust are involved), and often the second form flows into the first.

In turn, wet fogs, the formation of which is directly influenced by nature - this is evening, night or morning fog (this period is optimal for the formation of clouds creeping along the ground), meteorologists are also divided into groups:

1. Underground. Evening or morning fog that spreads low over the earth's surface or body of water (for example, fog over a river). The shroud may be continuous, or it may be in separate wisps, and visibility will not exceed a kilometer.
2. Translucent. Despite the fact that visibility along the surface is low and in some cases does not exceed several meters, clouds can be clearly distinguished in the sky. This type includes night, evening, and morning fog.
3. Solid. Visibility of dense fog is very limited and often does not exceed fifty meters. The sky is almost invisible, so it is almost impossible to distinguish clouds. This is mainly evening, night and morning fog, and during cold weather when the temperature rises temperature indicators cold fog can be seen during the day.

Why do fogs disappear?

The duration of this phenomenon varies and can range from half an hour to several days (especially during cold weather or when warm and cold air and water currents collide, for example, fog over a river). The main reason why any fog dissipates is the air warming up. Since a veil forms near the surface, after Sun rays it is heated, the air also heats up, as a result of which the drops evaporate and turn into steam.

The higher above the earth's surface, the weaker the fog dissipates, since in upper layers atmosphere, the air temperature begins to drop again, the steam transforms into water droplets and forms clouds.

The summer fog by the river is incredibly beautiful. Only in such moments do you understand how good it is to live! And the distant shores, hidden by a foggy haze, evoke lyrical memories and dreams.

However, even the most inveterate esthete will not always have an answer to the question of what fog is and what is the mechanism of its formation. If you don’t know this either, we invite you to read our article.

We should start with the fact that this natural phenomenon occurs when air heated during the day comes into contact with the cold surface of water or soil.

So what is fog? This is condensation in the form of tiny droplets (aerosol), which, collected in one place, sometimes reduce visibility to zero.

Note that the formation of fogs is impossible without solid or liquid particles called condensation nuclei. It is on them that water begins to precipitate, forming drops. It goes without saying that classic water fogs are formed only when the ambient temperature is not lower than -20 degrees Celsius. Otherwise, their ice form will form.

By the way, what is ice fog? In fact, their formation begins with the condensation of the same water on particles in the air, but due to the low temperature, these droplets instantly turn into the solid fraction. Considering that the refractive index of ice is higher, visibility in this case drops even more.

This will be confirmed to you by all drivers who have at least once worked in conditions Far North. In such conditions it is extremely difficult to drive a car, since there is almost no help. And the glass freezes over in a couple of minutes, so it’s simply impossible to see the road.

Most often, fog (the nature of which we have discussed) forms in the autumn, since the air during this period cools more slowly than the water or earth's surface. In the place where this natural phenomenon occurs, humidity atmospheric air strives for 100%.

As we have already said, the structure of the fog can be very different. The formation can be represented only by water droplets, water and ice, and also exclusively by ice crystals.

As you can see, fog is a multifaceted natural phenomenon, and therefore it is not surprising that there are several types of it:

• Solid type. Visibility is limited to almost zero, road traffic and aircraft flights are suspended.
• Smoky variety. Visibility is moderate, and the danger at low speeds is low.
• “Underground” - fog spreads at ground level.

On the shores of Canadian Newfoundland, all local residents are familiar with this natural phenomenon. The fact is that in these parts the Gulf Stream connects with the Labrador Current, which causes a strong temperature difference. For six months everything here is shrouded in a gloomy haze, and therefore pilots and sailors really do not like this area.

But there are places on our planet where fogs have never been seen. For example, this is the Indian city of Bombay. Well, the Chilean region hasn’t even seen rain in the last few hundred (or even thousands) years, so this natural phenomenon There's definitely nowhere to get it from.

So you have learned what fog is and where it comes from.

Fog is an accumulation of water droplets or ice crystals suspended in the ground layer of air, impairing horizontal visibility to 1000 m or less. In essence, it is a cloud lying on the surface of the earth or water.

Based on the main physical reasons, causing the formation of fogs, they can be divided into two main classes: cooling fogs and evaporation fogs. The first of these classes absolutely predominates.

Cooling fogs are formed by condensation or water vapor when air cools from the earth's or water's surface. They are divided into two types: radiative and advective.

Radiation fogs appear in conditions of stagnant air due to its nighttime cooling from the cooling underlying surface. Observed on clear, quiet nights and in the morning before sunrise. As soon as the sun's rays begin to warm up, these fogs quickly disappear.

Advection fogs are associated with cooling warm air when moving it to a cold surface (the formation of low stratus clouds, which can turn into fog when descending). These are the most powerful and lasting fogs. They are observed at any time of the day and can be transported over long distances.

Evaporation fogs (vapor) are formed due to the evaporation of water vapor from an underlying surface warmer than the air. Such fogs are most intense in winter over non-freezing bays and polynyas; over rivers and lakes they appear more often in autumn, and on land - after heavy rains in the evening and at night in the summer - autumn period.

Most common feature The distribution of fogs over the earth's surface is an increase in their frequency at high latitudes. Depending on the conditions of formation, fogs in Russia have different continuous durations. In continental areas, short-term fogs prevail, lasting no more than 2–4 hours, and on the coasts northern seas they may not stop for several days.

In the European part of Russia, the largest number of days with fog is observed on the coast arctic seas, in high mountain areas, on the slopes of hills facing moisture-carrying streams. Particular attention should be paid to (), where the frequency of fogs is extremely high throughout the year. In some places, the average annual number of days with fog can reach 230–280, and their duration per year is 2050 hours. One fog lasts on average 9 hours.

Under monsoon circulation conditions Far East A large number of fogs are observed during the warm period of the year. On , and Kuril Islands in some years the number of days with fog can exceed 160–180 per year with a duration of 1000–1400 hours.

The annual cycle depends on geographical conditions: over continents, fogs most often form in autumn, over seas and oceans - in spring, when the water surface is coldest.

Fogs with visibility of 500–200 meters are already seriously impeding traffic. Fogs with visibility less than 50 m and lasting 12 hours or more are considered particularly dangerous weather phenomena and can completely paralyze the work of air and sea ports and ground transport. The average continuous duration of fog with visibility of 500 m or less is usually 2–4 hours, but in some cases they can persist for more than a day.

In large industrial centers, due to the large number of active condensation nuclei emitted industrial enterprises, fogs can form even in unsaturated air and are observed 1.5–2 times more often than in the surrounding area. In Yakutsk, for example, the duration of fogs in the city center is 1300 hours, and on the outskirts (near the airport) - 475 hours.

IN major cities In the North-West, the number of days with visibility less than 500 m can range from 6 to 65. The longest fogs with such visibility are observed here in autumn months. Their continuous duration is on average 3 hours. The maximum duration of fogs per year in some cities is close to 200–300 hours.