Precipitation as an atmospheric phenomenon. What are the precipitation
Precipitation - water in liquid or solid state, falling out of clouds or deposited from the air on earth's surface.
Rain
Under certain conditions, cloud drops begin to merge into larger and heavier ones. They can no longer be retained in the atmosphere and fall to the ground in the form rain.
hail
It happens that in summer the air rises quickly, picks up rain clouds and carries them to a height where the temperature is below 0 °. raindrops freeze and fall out hail(Fig. 1).
Rice. 1. Origin of hail
Snow
AT winter time in temperate and high latitudes, precipitation falls in the form of snow. Clouds at this time do not consist of water droplets, but of the smallest crystals - needles, which, when combined together, form snowflakes.
dew and frost
Precipitation that falls on 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 rain gauge or rain gauge (Fig. 2).
Rice. 2. The structure of the rain gauge: 1 - outer case; 2 - funnel; 3 - a container for collecting oxen; 4 - measuring tank
Classification and types of precipitation
Precipitation is distinguished by the nature of precipitation, by origin, by physical condition, seasons of precipitation, etc. (Fig. 3).
According to the nature of the precipitation, there are torrential, continuous and drizzling. Rainfall - intense, short, capture a small area. Overhead precipitation - medium intensity, uniform, long (can last for days, capturing large areas). Drizzling precipitation - fine-drop precipitation falling over a small area.
By origin, precipitation is distinguished:
- convective - are characteristic of the hot zone, where heating and evaporation are intense, but often occur in temperate zone;
- frontal - formed when two people meet air masses With different temperatures and fall out of warmer air. Characteristic for temperate and cold zones;
- orographic - fall on the windward slopes of mountains. They are very plentiful 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 amount precipitation on the Amazonian lowland and in the Sahara desert, one can be convinced of their uneven distribution (Fig. 4). What explains this?
Precipitation is brought by moist air masses that form 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 over land there are continuous rains, as on the Pacific coast of Eurasia.
The constant winds also play big role in the distribution of precipitation. Thus, the trade winds blowing from the continent bring dry air to northern Africa, where the largest desert in the world, the Sahara, is located. westerly winds bring rain to Europe from the Atlantic Ocean.
Rice. 4. Average annual distribution of precipitation on the Earth's land
As you already know, sea currents affect precipitation in the coastal parts of the continents: warm currents contribute to their appearance (Mozambique current off the eastern coast of Africa, Gulf Stream off the coast of Europe), cold ones, on the contrary, prevent precipitation (Peruvian current off the western coast of South America) .
The relief also affects the distribution of precipitation, for example, the Himalayan mountains do not allow moist winds blowing north from indian ocean. Therefore, up to 20,000 mm of precipitation sometimes falls a year on their southern slopes. Humid air masses, rising along the slopes of the mountains (ascending air currents), cool, saturate, 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 rainfall. At the equator - in the belt low pressure— constantly heated air; as it rises, it cools and becomes saturated. Therefore, in the region of the equator, a lot of clouds form and there are heavy rains. There is also a lot of precipitation in other areas the globe where low pressure prevails. Wherein great importance air temperature has: the lower it is, the less precipitation falls.
In belts high pressure descending air currents predominate. The air, descending, heats up and loses the properties of the state of saturation. Therefore, at latitudes of 25-30 °, precipitation is rare and in small quantities. High-pressure areas near the poles also receive little precipitation.
Absolute maximum precipitation registered on about. Hawaii ( Pacific Ocean) - 11,684 mm/year and in Cherrapunji (India) - 11,600 mm/year. Absolute minimum - in the Atacama Desert and the Libyan Desert - less than 50 mm / year; sometimes precipitation does not fall at all for years.
The moisture content of an area is moisture factor- the ratio of annual precipitation and evaporation for the same period. The moisture coefficient is denoted by the letter K, the annual rainfall is denoted by the letter O, and the evaporation rate is denoted by I; then K = O: I.
The lower the humidity coefficient, the drier the climate. If the annual precipitation is approximately equal to evaporation, then the moisture coefficient is close to unity. In this case, moisture is considered sufficient. If the moisture index is greater than one, then the moisture excess, less than one - insufficient. If the moisture coefficient is less than 0.3, moisture is considered meager. Zones with sufficient moisture include forest-steppes and steppes, while zones with insufficient moisture include deserts.
Precipitation is water that falls from the atmosphere onto the earth's surface. Atmospheric precipitation also has a more scientific name - hydrometeors.
They are measured in millimeters. To do this, measure the thickness of the water that has fallen to the surface with the help of special instruments - precipitation gauges. If you need to measure the water column on large areas then weather radars are used.
On average, our Earth receives almost 1000 mm of precipitation annually. But it is quite predictable that their amount of moisture that has fallen out depends on many conditions: the climate and weather conditions, the terrain, and the proximity of water bodies.
Types of precipitation
Water from the atmosphere falls to 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 consider 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 into clouds, which consist of tiny drops, ranging in size from 0.05 to 0.1 mm. These tiny droplets in the clouds merge with each other over time, becoming larger 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 the cloud, they spill onto the ground in the form of rain.
Summer it's raining in the form of large drops. They remain large because the heated air rises from the ground. It is these ascending jets that do not allow drops to break into smaller ones.
But in spring and autumn, the air is much cooler, so at these times of the year the rains are drizzling. Moreover, if the rain comes from stratus clouds, it is called oblique, and if the drops begin to fall from the kune-rain, then the rain turns into a downpour.
Almost 1 billion tons of water is poured onto our planet every year in the form of rain.
It is worth highlighting in a separate category drizzle. This type of precipitation also falls from stratus clouds, but its drops are so small and their speed is so negligible that the water droplets seem to be suspended in the air.
Dew
Another type of liquid precipitation that falls at night or early in the morning. Dew drops are formed from water vapor. During the night, this vapor cools, and the water turns from a gaseous state into a liquid one.
The most favorable conditions for the formation of dew: clear weather, warm air and almost no wind.
Solid atmospheric precipitation
We can observe solid precipitation during the cold season, when the air cools to such an extent that the water droplets in the air freeze.
Snow
Snow, like rain, forms in clouds. 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 in the form of snow. Each drop freezes in the form of a kind of crystal. Scientists say that all snowflakes have different shape and it is simply impossible to find the same.
By the way, snowflakes fall very slowly, since they are almost 95% air. For the same reason they white color. And the snow crunches underfoot because the crystals break. And our ears are able to pick up this sound. But for fish, this is a real torment, since snowflakes falling on the water emit a high-frequency sound that fish hear.
hail
falls only in the warm season, especially if it was very hot and stuffy the day before. The heated air rushes up in strong streams, carrying the evaporated water with it. Heavy cumulus clouds form. Then, under the influence of ascending currents, the water droplets in them become heavier, begin to freeze and grow into crystals. It is these lumps of crystals that rush to the ground, increasing in size along the way due to merging with drops of supercooled water in the atmosphere.
It should be borne in mind that such ice "snowballs" rush to the ground with incredible speed, and therefore hail is able to break through slate or glass. Hail does a lot of damage agriculture, so the most "dangerous" clouds that are ready to burst into hail are dispersed with the help of special guns.
Frost
Hoarfrost, like dew, is formed from water vapor. But in winter and autumn months When it is already cold enough, the water droplets freeze and therefore fall out as a thin layer of ice crystals. And they do not melt because the earth cools even more.
rainy seasons
In the tropics and very rarely in temperate latitudes there comes a time of the year when it falls out of proportion a large number of precipitation. This period is called the rainy season.
In countries that are located in these latitudes, there are no severe winters. But spring, summer and autumn are incredibly hot. During this hot period, a huge amount of moisture accumulates in the atmosphere, which then pours out in the form of prolonged rains.
At the equator, the rainy season occurs twice a year. And in the tropical zone, south and north of the equator, such a season happens only once a year. This is due to the fact that the rain belt gradually runs from south to north and back.
Water that falls on the Earth's surface in the form of rain, snow, hail or condensed on objects as frost or dew is called precipitation. Precipitation can be heavy rainfall associated with warm fronts or showers associated with cold fronts.
The appearance of rain is due to the merging of small droplets of water in a cloud into larger ones, which, overcoming gravity, fall to the Earth. If the cloud contains small particles solids(dust particles), the condensation process proceeds faster, since they act as condensation nuclei. At negative temperatures, the condensation of water vapor in the cloud leads to snowfall. If snowflakes from the upper layers of the cloud fall into the lower layers with a higher temperature, which contains a large number of cold drops of water, then the snowflakes combine with water, losing their shape and turning into snowballs up to 3 mm in diameter.
Precipitation formation
Hail is formed in clouds of vertical development, characteristic features which is the presence of positive temperatures in the lower layer and negative - in the upper. In this case, spherical snowballs with ascending air currents rise to the upper parts of the cloud with more low temperatures and solidify with the formation of spherical ice - hailstones. Then, under the influence of gravity, the hailstones fall to the Earth. They usually vary in size and can be as small as a pea to a chicken egg.
Types of precipitation
Such types of precipitation as dew, hoarfrost, hoarfrost, ice, fog, are formed in the surface layers of the atmosphere due to the condensation of water vapor on objects. Dew appears at more high temperatures, frost and frost - with negative. With an excessive concentration of water vapor in the surface atmospheric layer, fog appears. If fog mixes with dust and dirt in industrial cities, it is called smog. 
Precipitation is measured by the thickness of the water layer in millimeters. On our planet, on average, about 1000 mm of precipitation falls annually. A rain gauge is used to measure the amount of precipitation. For many years, observations have been made of the amount of precipitation in different regions of the planet, thanks to which the general patterns of their distribution over the earth's surface have been established.
The maximum amount of precipitation occurs in equatorial belt(up to 2000 mm per year), the minimum - in the tropics and polar regions(200-250 mm per year). In the temperate zone, the average annual rainfall is 500-600 mm per year.
In every climate zone there is also irregularity in precipitation. This is due to the peculiarities of the relief of a certain area and the prevailing wind direction. For example, on the western outskirts of the Scandinavian mountain range, 1000 mm falls per year, and on the eastern outskirts - more than two times less. Areas of land were identified, on which precipitation is almost completely absent. These are the Atacama Deserts, the central regions of the Sahara. In these regions, the average annual rainfall is less than 50 mm. Great amount rainfall is recorded in southern regions Himalayas, in Central Africa(up to 10000 mm per year).
Thus, the determining features of the climate of a given area are the average monthly, seasonal, average annual precipitation, their distribution over the Earth's surface, and intensity. These climate features have a significant impact on many sectors of the human economy, including agriculture.
Related content:
Municipal educational institution
the main comprehensive school in the village of Severny.
Public lesson on this topic:
"Precipitation"
6th grade
Geography teacher
Zinovieva Yu. A.
Lesson topic: "Atmospheric precipitation"
Target: to form the concept of "atmospheric precipitation" among students.
Tasks: Educational: expand knowledge about precipitation, identify the causes of formation various kinds atmospheric precipitation and their significance.
Developing: continue to develop techniques for reading climate charts. Develop the ability to work with geographical maps, tables, analyze, summarize and draw conclusions.
Educational: promote interest in the subject.
During the classes.
Organizing time
Repetition of the studied material (survey on cards)
Card number 1.
(solid, liquid, gaseous).
What types of clouds do you know? (cumulus, stratus, pinnate).
(4: 9*100 = 44,4%) .
Card number 2
(clouds are fog that has risen to a height).
How is fog formed? (air saturated with water vapor comes into contact with the cooled earth's surface).
(14: 17*100 = 82,4%) .
Card number 3
(cumulus)
How are clouds formed? (clouds form when rising air cools).
(2: 5*100 = 40%).
Learning new material.
Precipitation- water in a liquid or solid state, falling out of clouds or deposited from the air on the earth's surface and objects on it.
Types of precipitation:
A) falling out of the clouds:
rain - 0.5-7 mm (average 1.5 mm),
snow - hexagonal ice crystals,
hail - large pieces of ice from 7 mm to 8 cm, falls from cumulonimbus clouds. The largest hailstone - India - 1kg, 13cm
groats - ice, snow - rounded nucleoli 1 mm or more,
drizzle - small drops up to 0.5 mm.
B) released from the air:
fog - accumulation of water in the air, when the smallest condensation products of water vapor are formed (at air temperatures above -10 ° these are the smallest droplets of water, at -10 ... -15 ° - a mixture of water droplets and ice crystals, at temperatures below -15 ° - crystals ice, sparkling in the sun or in the light of the moon and lanterns),
frost - a white crystalline precipitate that forms on the surface of the earth as a result of the transition from a gaseous state to a solid state of water vapor contained in the air at a negative soil temperature (up to 3 mm thick).
dew - droplets of water formed on the surface of the earth as a result of condensation of water vapor at a positive temperature of air and soil, a cloudy sky and light wind.
ice - a layer of dense vitreous ice that forms on plants, wires, objects, the surface of the earth as a result of freezing of precipitation particles in contact with a surface that has a negative temperature. It is observed at air temperatures most often from zero to −10 °,
frost - a species that is a crystalline or granular deposits on thin and long objects (tree branches, wires) in wet, frosty weather.
Reasons for the formation of precipitation:
Do you think precipitation falls from each cloud? How is precipitation formed?
Let's look at Fig. 80 on page 25 and try to answer these questions.
Now let's fill in the table:
TYPE OF RAIN
RAIN
SNOW
GRAD
At whatt air are formed
At the surface of the earth - positive, in the clouds - below 0 ° С
What time of year does it fall
Spring, summer, autumn, sometimes winter (during thaws)
In winter, late autumn, in early spring
What clouds do they fall from?
Cumulonimbus, nimbostratus
layered
Cumulonimbus
Conclusion: Precipitation falls from clouds that are at different heights and contain different amounts of moisture.
Fizminutka
Precipitation difference(composing a cluster).
According to the nature of occurrence:
A) liquid - rain, dew, drizzle
B) solid - snow, cereals, hail, hoarfrost, frost, ice.
Precipitation is classified according to the type of precipitation
A) showers - a rapid change in intensity, short-lived (cumulonimbus clouds, often with hail)
B) oblique - uniform, long-term (nimbostratus clouds)
C) drizzling - in the form of drizzle (stratus, stratocumulus clouds)
Differences in precipitation by origin.
A) convective precipitation - intense heating and evaporation (hot zone)
B) frontal precipitation - the meeting of two different air masses (temperate and cold zones)
C) orographic - fall on the windward slopes of mountains
Precipitation
According to the nature of the drop
Origin
According to the nature of occurrence
Measuring the amount of precipitation.
Exist special devices to measure the amount of precipitation
rain gauge- a device for measuring liquid atmospheric precipitation
snow gauge designed to measure the height and density of the snow cover.
Precipitation
The amount of precipitation per day is calculated by adding the results of two measurements.
Monthly rainfall equal to the sum of precipitation for all days of that month.
Annual precipitation is the sum of precipitation for all months of the year.
Working with a climatogram
Sediments of our region.
What types of precipitation are typical for our area?
Suggested answer: spring, summer and autumn in Saratov region Precipitation falls in the form of rain, hail, in winter - in the form of snow. Sometimes it can rain in the form of rain during the winter.
Summary of the lesson.
Having studied the material of today's lesson, we determined the types of precipitation, the causes of their precipitation, learned how to read precipitation diagrams, and found out what precipitation is typical for our area.
As a result of our work, we have compiled a scheme (cluster) "Types of precipitation".
Card number 1.
What kind aggregate states water you know?
What types of clouds do you know?
Absolute humidity at a temperature of +10 o C is 4 g of water vapor. Determine relative humidity this air.
Card number 2
What do clouds and fog have in common?
How is fog formed?
Absolute humidity at a temperature of +20 ° C is 14 g of water vapor. Determine the relative humidity of this air.
Card number 3
What clouds look like white heaps of cotton wool scattered across the sky?
How are clouds formed?
Absolute humidity at 0°C is 2 g of water vapor. Determine the relative humidity of this air.
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