Precipitation- water in a liquid or solid state that falls from clouds or settles from the air onto earth's surface.
Rain
Under certain conditions, cloud droplets begin to merge into larger and heavier ones. They can no longer stay in the atmosphere and fall to the ground in the form rain.
hail
It happens that in the summer the air quickly rises and picks up rain clouds and carries them to a height where the temperature is below 0°. Raindrops freeze and fall as hail(Fig. 1).
Rice. 1. Origin of the hail
Snow
IN winter time in temperate and high latitudes precipitation falls in the form snow. Clouds at this time do not consist of water droplets, but of tiny crystals - needles, which, joining together, form snowflakes.
Dew and frost
Precipitation falling onto the earth's surface not only from clouds, but also directly from the air is dew And frost.
The amount of precipitation is measured by a precipitation gauge or rain gauge (Fig. 2).
Rice. 2. Structure of the rain gauge: 1 - outer casing; 2 - funnel; 3 - container for collecting oxen; 4-dimensional tank
Classification and types of precipitation
Precipitation is distinguished by the nature of precipitation, by origin, by physical state, by seasons of precipitation, etc. (Fig. 3).
According to the nature of precipitation, precipitation can be torrential, heavy and drizzling. Rainfall - intense, short-lived, cover a small area. Cover precipitation - medium intensity, uniform, long-term (can last for days, capturing large areas). Drizzle - fine precipitation falling over a small area.
Precipitation is classified according to its origin:
- convective - characteristic of the hot zone, where heating and evaporation are intense, but often occur in the temperate zone;
- frontal - are formed when two air masses meet different temperatures and fall out of warmer air. Characteristic for temperate and cold zones;
- orographic - fall on the windward slopes of the mountains. They are very abundant if the air comes from the side warm sea and has high absolute and relative humidity.
Rice. 3. Types of precipitation
Comparing to climate map annual quantity atmospheric precipitation in the Amazonian lowland and in the Sahara desert, one can see their uneven distribution (Fig. 4). What explains this?
Precipitation brings wet air masses, forming over the ocean. This is clearly seen in the example of territories with monsoon climate. The summer monsoon brings a lot of moisture from the ocean. And there are continuous rains over the land, as on the Pacific coast of Eurasia.
Constant winds also play a big role in the distribution of precipitation. Thus, trade winds blowing from the continent bring dry air to northern Africa, where the most vast desert world - Sahara. Western winds bring rain to Europe from the Atlantic Ocean.
Rice. 4. Average annual distribution of precipitation on Earth's land
As you already know, sea currents affect precipitation in the coastal parts of continents: warm currents contribute to their appearance (the Mozambique Current off the eastern coast of Africa, the Gulf Stream off the coast of Europe), cold weather, on the contrary, prevents precipitation ( Peruvian Current off the western coast of South America).
Relief also affects the distribution of precipitation, for example, the Himalayan mountains do not allow moist winds blowing from the Indian Ocean to pass to the north. Therefore, on their southern slopes sometimes up to 20,000 mm of precipitation falls per year. Moist air masses, rising along the mountain slopes (ascending air currents), cool, become saturated, and precipitation falls from them. The territory north of the Himalayan mountains resembles a desert: only 200 mm of precipitation falls there per year.
There is a relationship between belts and precipitation. At the equator - in the belt low pressure— constantly heated air; rising upward, it cools and becomes saturated. Therefore, in the equator region there are many clouds and heavy rainfall. A lot of precipitation also falls in other areas of the globe where low pressure prevails. Wherein great importance has an air temperature: the lower it is, the less precipitation falls.
In belts high pressure downward air currents predominate. As the air descends, it heats up and loses the properties of its saturation state. Therefore, at latitudes 25-30° precipitation occurs rarely and in small quantities. Areas of high pressure near the poles also receive little precipitation.
Absolute maximum precipitation registered on o. Hawaii ( Pacific Ocean) - 11,684 mm/year and in Cherrapunji (India) - 11,600 mm/year. The absolute minimum - in the Atacama Desert and the Libyan Desert - less than 50 mm/year; Sometimes there is no precipitation at all for years.
The moisture content of the area is characterized by humidification coefficient— the ratio of annual precipitation and evaporation for the same period. The humidification coefficient is denoted by the letter K, the annual amount of precipitation by the letter O, and evaporation by the letter I; then K = O: I.
The lower the humidification coefficient, the drier the climate. If the annual precipitation is approximately equal to evaporation, then the humidification coefficient is close to unity. In this case, hydration is considered sufficient. If the moisture level more than one, then hydration excessive, less than one - insufficient. When the humidification coefficient is less than 0.3, humidification is considered meager. Zones with sufficient moisture include forest-steppes and steppes, and zones with insufficient moisture include deserts.
First of all, let’s define the concept itself “ precipitation" In the Meteorological Dictionary, this term is interpreted as follows: “Precipitation is water in a liquid or solid state that falls from clouds or settles from the air on the surface of the earth and on objects.”
According to the above definition, precipitation can be divided into two groups: precipitation released directly from the air - dew, frost, frost, ice, and precipitation falling from clouds - rain, drizzle, snow, snow pellets, hail.
Each type of precipitation has its own characteristics.
Dew represents tiny droplets of water deposited on the surface of the earth and on ground objects (grass, tree leaves, roofs, etc.). Dew forms at night or in the evening in clear, calm weather.
Frost appears on surfaces cooled below 0 °C. It is a thin layer crystal ice, the particles of which resemble snowflakes in shape.
frost- this is the deposition of ice on thin and long objects (tree branches, wires), which forms at any time of the day, usually in cloudy, foggy weather with negative temperatures(below - 15°C). Frost can be crystalline and granular. On vertical objects, frost is deposited mainly on the windward side.
Among the sediments deposited on the earth's surface, special meaning It has black ice. It is a layer of dense transparent or muddy ice, growing on any objects (including trunks and branches of trees, bushes) and on the surface of the earth. Formed at air temperatures from 0 to -3°C due to the freezing of drops of supercooled rain, drizzle or fog. A crust of frozen ice can reach a thickness of several centimeters and cause branches to break off.
Precipitation falling from clouds is divided into drizzle, heavy and shower.
Drizzle (drizzle) consist of very small drops of water with a diameter of less than 0.5 mm. They are characterized by low intensity. This precipitation usually falls from stratus and stratocumulus clouds. The speed at which the droplets fall is so slow that they appear to be suspended in the air.
Cover precipitation- this is rain consisting of small drops of water, or snowfall of snowflakes with a diameter of 1-2 mm. This is long-term precipitation that falls from dense altostratus and nimbostratus clouds. They can continue for several hours and even days, covering vast areas.
Rainfall characterized by high intensity. These are large droplets and uneven precipitation, falling in both liquid and solid form (snow, graupel, hail, sleet). The downpour can last from a few minutes to several hours. The area covered by a rainstorm is usually small.
hail, always observed during a thunderstorm, usually together with heavy rain, is formed in cumulonimbus (thunderstorm) clouds of vertical development. It usually falls in spring and summer in a narrow strip and most often between 12 and 17 hours. The duration of hail is measured in minutes. Within 5-10 minutes, the ground can be covered with a layer of hailstones several centimeters thick. During intense hail, plants may be damaged varying degrees or even destroyed.
Precipitation is measured by the thickness of the water layer in millimeters. If 10 mm of precipitation fell, this means that the layer of water that fell on the surface of the earth is equal to 10 mm. What does 10 mm of precipitation mean for an area of 600 m2? It's not hard to calculate. Let's start the calculation for an area equal to 1 m2. For her, this amount of precipitation will be 10,000 cm 3, i.e. 10 liters of water. And this is a whole bucket. This means that for an area of 100 m2, the amount of precipitation will already be equal to 100 buckets, but for an area of six acres - 600 buckets, or six tons of water. This is what 10 mm of rainfall is for a typical garden plot.
Clouds contain atmospheric water, which falls to the ground in the form of precipitation - raindrops, snowflakes or hailstones.
In the troposphere, bottom layer The atmosphere contains huge reserves of water - in the form of steam, small drops or ice crystals. This amount would be enough to cover the entire planet with a layer one meter thick, if, of course, all this water could fall to the ground at once, which does not happen. Only stratus and cumulus clouds are capable of returning water in the form of rain, snow and hail. Some water also falls with dew and frost.
From the smallest droplets to rain
Moisture is found in clouds in the form of tiny ice crystals or water droplets. While these particles are small, they can remain suspended, floating in rising air currents. When there are a lot of such particles, they combine into larger ones. Drops formed from millions of tiny droplets are already heavy enough to fall to the ground. This is how rain occurs in warm latitudes.
IN temperate zone The formation of raindrops is usually preceded by the appearance of snowflakes. In the upper layers of clouds, the temperature is almost always below zero, so water condenses here in the form of ice crystals. When there are a lot of them, they stick together, forming snowflakes. As snowflakes descend to the ground, they fall into increasingly warmer layers of air. If they find themselves in a layer with a temperature above zero before they reach the surface of the earth, they melt, turn into drops of water and fall as rain.
26,000 liters per square meter
If the atmosphere is relatively homogeneous and the rising air currents are weak, droplets or water crystals suspended in the air do not reach large sizes. Then it can be drizzling for a long time, the drops of which are less than 0.5 mm in diameter. Typically, such rain forms in dense stratus clouds covering large areas.
In unstable weather with strong winds Cumulus clouds of large vertical development often form, within which active convective air movement occurs, promoting the formation of large droplets. The resulting localized heavy rains usually do not last long. Air friction limits the falling speed (no more than 8 m/s) and the size of the droplets. Drops with a diameter of 6 mm are crushed into smaller ones.
The largest cumulonimbus clouds can shed thousands of tons of water per second over an area of tens of square kilometers. In 1952, on one section of Reunion Island in Indian Ocean 1,872 liters per 1 m2 fell per day - almost twice as much as in Paris for the whole year. But even this is not a record yet. In 1860-1861 rain gauges (installations for measuring precipitation) recorded 12 exclusively wet months in one of the regions of India: it was a real flood, when more than 26,000 liters of water fell per 1 m2.
Floods
Flash floods, or flash floods, occur after heavy rains, when rivers do not have time to carry away the water entering them and overflow their banks. In addition, the flow speed increases sharply, and leisurely rivers often become violent. Such floods usually occur in mountains, foothills, gorges, and on densely built-up slopes. Sometimes they develop within a few hours.
Powerful flash floods often carry with them large volumes of soil, stones, branches, and entire trees washed away from slopes. They destroy bridges and houses and often cause death. On the plains, river floods cause less rapid flooding. Usually the water rises gradually, over several days, in the spring after the snow melts or in the fall after heavy rains. During spring floods and autumn floods, rivers overflow widely, covering large areas with water. Flooding is increasing due to rising groundwater, artificial or natural obstacles located downstream and slowing down the movement of water. Cutting forests, fencing around cropland, and building houses and roads can all impede flow. As a result less water goes underground, and the rivers overflow more. In estuarine areas, sea tides can also delay runoff river water and increase flooding. Floods caused by typhoons at the mouth of the Ganges lead to terrible disasters in Bangladesh. Thus, in 1991, about 150 thousand people died in the country due to rising waters. In China, over the past 3,500 years, there have been almost 1,500 severe floods on the Yellow River, causing the death of millions of people.
Giant hailstones
If the ice crystals that form in the clouds do not all melt completely as they fly towards the ground, snowing with the rain. If falling crystals fall into a warm cloud layer, where there are many tiny drops of water, then snow pellets are formed.
In clouds with a large vertical temperature contrast, strong upward and downward air currents develop. As a result, the crystals repeatedly fall into the warm zone of the cloud, where new droplets of water settle on them, and then rise again into the cold zone, where the settled water freezes. This is how hailstones are formed layer by layer. When these ice balls become so heavy that the rising air currents can no longer hold them, the hailstones fall to the ground. Usually their diameter is from 0.5 to 5 cm. But there were also huge specimens - almost 20 cm in diameter. Like cannonballs, they flew down at a speed of about 40 m/s. If not only in the upper layers of the cloud, but also along the entire path of precipitation to the ground, the temperature is below zero, snow falls. Snowflakes can reach several centimeters in diameter.
You might be interested in:
2403
Hello Dear friends! In this article I want to tell you about how various sediments are formed, what kind of process it is and where it is formed.
We have all seen various precipitation in our lives, but most likely we have never thought about where it is formed from, what types of precipitation there are, and what processes are involved in all this, how to determine what the weather will be like tomorrow... Let's consider precipitation and its types.
Precipitation- this is the moisture contained in which falls to the Earth in different types: snow, rain, hail, etc. Precipitation is measured by the thickness of the fallen ball of water in millimeters. On average per year globe About 1000 mm of precipitation falls per year, and in high latitudes and deserts - less than 250 mm per year.
Tiny droplets of water vapor in a cloud move up and down rather than hanging. When they fall down, they merge with other droplets of water, but their weight will not allow them to break through the rising air that created them. This process is called “coalescence” (fusion). Let's discuss with you the main types of precipitation.
According to Swedish meteorologist Bergeron's theory, which was put forward in the 1930s, snow and rain are caused by supercooled water droplets that form ice crystals in clouds. Depending on whether these crystals melt during the fall or not, they fall to Earth in the form of rain or snow.
As crystals move up and down in the clouds, new layers grow on them, thus hail forms. This process is called “accretion” (growth).
When water vapor at temperatures from -4°C to -15°C condenses in a cloud, ice crystals stick together and form into snowflakes, thus snow forms.
The shape and size of snowflakes depend on the air temperature and the strength of the winds in which they fall. On the surface, snowflakes form a snow cover that reflects more than half of the sun's ray energy, and the purest and driest snow reflects up to 90% of the sun's rays.
This cools snow-covered areas. Snow cover capable of emitting thermal energy, and therefore even the slight heat that it has quickly goes into the atmosphere.
The resulting water when water vapor condenses is rain. It falls from the clouds and reaches the Earth's surface in the form of liquid droplets. Heavy, light and moderate (storm) rains are distinguished depending on the volume of precipitation that fell in a certain period of time.
The intensity of light rain varies from very low to 2.5 mm/h; moderate rain - from 2.8 to 8 mm/h and with heavy rain more than 8 mm/h or more than 0.8 mm in 6 minutes. When there is continuous cloud cover over a large area, there are continuous continuous rains, usually weak and consisting of small droplets.
In smaller areas, rainfall tends to be more intense and consist of larger droplets. Atmospheric precipitation in the form of very small droplets that fall very slowly from fog or clouds is drizzle.
Other precipitations are also distinguished: freezing rain, ice pellets, snow grains, snow pellets, etc. But I will not write about this, because from the example of basic precipitation written above, you can now clearly understand all these meanings. All this precipitation has the following consequences: ice, frozen trees... and they are very similar to each other.
Cloudiness.
Her can be determined by eye. It varies in oktas on an 8-point scale. For example, 0 oktas – cloudless sky, 4 oktas – half the sky is covered with clouds, 8 oktas – completely cloudy. The weather can be determined without weather forecasts.
It has a local character: somewhere it’s raining, but a few kilometers away it’s standing clear weather. Sometimes it may not be kilometers, but meters (it’s clear on one side of the street, but it’s raining on the other), I myself have repeatedly witnessed such rain.
Many fishermen and residents rural areas, as well as older people, are able to predict the weather in their area much better by studying clouds.
During sunset, red clouds in the sky often guarantee clear weather the next day. Thunderstorms in summer and hail in winter carry copper-colored clouds with bright silvery edges. The storm is foreshadowed by the dawn sky covered with blood-red spots.
The end of a period of stable weather is often heralded by a sky covered in “lamblets” of cirrocumulus clouds. Changes in weather are often indicated by cirrus clouds ("horses tails") high in the sky. Thunderstorms with rain, snow or hail usually bring cumulonimbus clouds.
You can find out more about all types of clouds
Well, now we have looked at all the precipitation that is important to us, and we know the main signs of the weather 🙂
Atmospheric precipitation is the name given to water that falls from the atmosphere onto the earth's surface. Atmospheric precipitation has more scientific name- hydrometeors.
They are measured in millimeters. To do this, measure the thickness of water that has fallen to the surface using special instruments - precipitation gauges. If you need to measure the water thickness at large areas, then use weather radars.
On average, our Earth receives almost 1000 mm of precipitation annually. But it is quite predictable that the amount of moisture that falls depends on many conditions: climate and weather conditions, terrain and proximity to water bodies.
Types of precipitation
Water from the atmosphere falls onto the earth's surface, being in its two states - liquid and solid. According to this principle, all atmospheric precipitation is usually divided into liquid (rain and dew) and solid (hail, frost and snow). Let's look at each of these types in more detail.
Liquid precipitation
Liquid precipitation falls to the ground in the form of water droplets.
Rain
Evaporating from the surface of the earth, water in the atmosphere collects in clouds, which consist of tiny droplets, ranging in size from 0.05 to 0.1 mm. These miniature droplets in the clouds merge with each other over time, becoming larger in size and noticeably heavier. Visually, this process can be observed when the snow-white cloud begins to darken and become heavier. When there are too many such drops in a cloud, they fall to the ground in the form of rain.
In summer It is raining in the form of large drops. They remain large because heated air rises from the ground. These rising jets prevent the drops from breaking into smaller ones.
But in spring and autumn the air is much cooler, so at these times of the year the rain is drizzling. Moreover, if the rain comes from stratus clouds, it is called cover clouds, and if drops begin to fall from nimbus clouds, then the rain turns into downpour.
Every year, almost 1 billion tons of water fall on our planet in the form of rain.
It is worth highlighting in a separate category drizzle. This type of precipitation also falls from stratus clouds, but the droplets are so small and their speed is so negligible that the water droplets appear suspended in the air.
Dew
Another view liquid precipitation, which falls at night or early in the morning. Dew droplets are formed from water vapor. During the night this steam cools, and the water from gaseous state turns into liquid.
The most favorable conditions for dew formation: clear weather, warm air and almost complete absence of wind.
Solid precipitation
We can observe solid precipitation in the cold season, when the air cools to such an extent that water droplets in the air freeze.
Snow
Snow, like rain, forms in a cloud. Then, when the cloud enters a stream of air in which the temperature is below 0°C, the water droplets in it freeze, become heavy and fall to the ground as snow. Each droplet solidifies into a kind of crystal. Scientists say that all snowflakes have different shapes and it is simply impossible to find identical ones.
By the way, snowflakes fall very slowly, since they are almost 95% air. For the same reason they white. And the snow crunches underfoot because the crystals are breaking. And our hearing is able to catch this sound. But for the fish it’s a real torment, since snowflakes falling on the water emit a high-frequency sound that the fish hear.
hail
falls only in the warm season, especially if the day before it was very hot and stuffy. The heated air rushes upward in strong currents, carrying with it the evaporated water. Heavy cumulus clouds form. Then, under the influence of rising currents, the water droplets in them become heavier, begin to freeze and become overgrown with crystals. These lumps of crystals rush to the ground, increasing in size along the way due to merging with drops of supercooled water in the atmosphere.
It must be taken into account that such icy “snowballs” rush to the ground with incredible speed, and therefore hail is capable of breaking through slate or glass. Hail causes big damage agriculture, therefore, the most “dangerous” clouds that are ready to burst into hail are dispersed with the help of special guns.
Frost
Frost, like dew, is formed from water vapor. But in winter and autumn months When it's cold enough, the water droplets freeze and therefore fall out as a thin layer of ice crystals. But they don’t melt because the earth is cooling even more.
Rainy seasons
In the tropics and very rarely in temperate latitudes there comes a time of year when there is an excessive amount of rainfall a large number of precipitation. This period is called the rainy season.
In countries located at these latitudes, there is no harsh winters. But spring, summer and autumn are incredibly hot. During this hot period, accumulates great amount moisture in the atmosphere, which then pours out in the form of prolonged rains.
In the equator region, the rainy season occurs twice a year. And in tropical zone, south and north of the equator, such a season occurs only once a year. This is due to the fact that the rain belt gradually runs from south to north and back.
Loading...
