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The training started on November 5, 2015
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Topic #1: The main characteristics of the weather.
Main atmospheric phenomena
December 25, 2013 19: 00
The structure of the Earth's atmosphere
First of all, we need to understand what the atmosphere and meteorology are.
The atmosphere is the gas envelope of a celestial body, held near it by gravity.
Meteorology is the science of the structure and properties of the Earth's atmosphere and the physical processes taking place in it.
The lower boundary of the atmosphere coincides with the Earth's surface, since air penetrates into the smallest pores in the soil and is dissolved even in water.
The upper boundary at an altitude of 2000-3000 km gradually passes into outer space.
There are several layers in the atmosphere that differ in temperature and density (see the figure).
The troposphere is the lowest layer of the atmosphere, the thickness of which is 8-10 km above the poles, 10-12 km in temperate latitudes, and 16-18 km above the equator.
The air in the troposphere is heated from the Earth's surface, i.e. from land and water.
Therefore, the air temperature in this layer decreases with altitude by an average of 0.6 °C for every 100 m.
At the upper boundary of the troposphere, it reaches -55 °C.
At the same time, in the area of the equator at the upper border of the troposphere, the air temperature is -70 °C, and in the area of the North Pole -65 °C.
About 80% of the atmospheric mass is concentrated in the troposphere, almost all water vapor is located, thunderstorms, storms, clouds and precipitation occur, as well as vertical (convection) and horizontal (wind) air movement occurs.
We can say that the weather is mainly formed in the troposphere.
Stratosphere — the layer of the atmosphere located above the troposphere at an altitude of 8 to 50 km.
The color of the sky in this layer seems to be purple, which is explained by the rarefaction of the air, because of which the sun's rays are almost not scattered.
20% of the mass of the atmosphere is concentrated in the stratosphere.
The air in this layer is rarefied, there is practically no water vapor, and therefore almost no clouds and precipitation are formed.
However, stable air currents are observed in the stratosphere, the speed of which reaches 300 km/h.
This layer contains ozone (the ozone shield, the ozonosphere), a layer that absorbs ultraviolet rays, preventing them from reaching the Earth and thereby protecting living organisms on our planet.
Due to ozone, the air temperature at the upper boundary of the stratosphere is in the range from -50 to -55 °C.
Between the mesosphere and the stratosphere there is a transition zone — the stratopause.
The mesosphere is a layer of the atmosphere located at an altitude of 50-80 km.
The air density here is 200 times less than that of the Earth's surface.
The color of the sky in the mesosphere seems black, stars are visible during the day.
The air temperature drops to -75 (-90)°C.
At an altitude of 80 km, the thermosphere begins.
The air temperature in this layer rises sharply to a height of 250 m, and then becomes constant: at an altitude of 150 km, it reaches 220-240 °C; at an altitude of 500-600 km, it exceeds 1500 °C.
In the mesosphere and thermosphere, under the influence of cosmic rays, gas molecules break up into charged (ionized) atomic particles, so this part of the atmosphere is called the ionosphere a layer of very rarefied air located at an altitude of 50 to 1000 km, consisting mainly of ionized oxygen atoms, nitrogen oxide molecules and free electrons.
This layer is characterized by high electrification, and long and medium radio waves are reflected from it, like from a mirror.
Auroras appear in the ionosphere — the glow of rarefied gases under the influence of electrically charged particles flying from the Sun — and sharp fluctuations in the magnetic field are observed.
The exosphere is the outer layer of the atmosphere located above 1000 km.
This layer is also called the scattering sphere, since gas particles move here at high speed and can be scattered into outer space.
The main characteristics of the atmosphere: atmospheric pressure, air temperature, air humidity.
As can be seen from the description of its structure, the atmosphere is characterized by several concepts: pressure, temperature and humidity.
Atmospheric pressure is the force with which air presses on the Earth's surface.
Atmospheric pressure is created by the gravitational attraction of air to the Earth.
Normal atmospheric pressure is considered to be a pressure equal to the pressure of a column of mercury with a height of 760 mm at a temperature of 0 °C.
The atmospheric pressure decreases as the altitude increases, since it is created only by the overlying layer of the atmosphere.
At low altitudes, every 12 m of ascent, the atmospheric pressure is reduced by 1 mm Hg.
At high altitudes, this pattern is violated.
The air temperature is, obviously, the temperature of the gas layer surrounding us.
With increasing altitude, the air temperature is constantly changing.
This change is called the temperature gradient.
The temperature gradient is a vertical vector reflecting the change (difference) in temperature in the atmosphere with altitude (in degrees per 100 m).
In the troposphere, and it is this layer of air that interests us, the temperature drops by an average of 0.6°C for every 100 m.
By the way, the air temperature continues to decrease to the thermosphere, and only there it makes a sharp jump up: from -90°C to 1500°C.
In addition, the temperature gradient (temperature change with increasing altitude) depends on the humidity of the air: in dry air, the temperature drops with an increase in altitude by about 1°C for every 100 m , in saturated water vapor - on average by 0.5°C.
Air humidity is the saturation of air with water vapor.
There is a concept of absolute and relative humidity of the air.
Absolute humidity is the amount of water vapor contained in 1 m3 of air.
It is expressed in grams.
For example, if they say "the absolute humidity is 15", it means that 1 m3 contains 15 g of water vapor.
Relative humidity is the ratio (as a percentage) of the actual water vapor content in 1 m3 of air to the amount of water vapor that can be contained in 1 m3 at a given temperature.
For example, if the radio during the transmission of the weather report reported that the relative humidity is 70%, it means that the air contains 70 % of the water vapor that it can hold at a given temperature.
The main characteristics of the weather: wind direction and strength, cloudiness, precipitation, visibility.
Depending on the combinations of the above characteristics, we say that today is good or bad weather, flying or non flying.
High relative humidity can lead to precipitation, the formation of clouds and fog.
And the difference in temperatures and pressures in different layers of air leads to the formation of wind.
So, let's start from the end of J
Wind.
The power of the wind.
The Beaufort scale.
Wind — the movement of air in a horizontal direction.
Winds are usually classified according to the scale, direction, speed, types of forces that cause them, places of propagation and impact on the environment.
The most important for us are the direction and speed of the wind.
In meteorology, the direction of the wind is the direction FROM WHICH the wind blows.
That is, the north wind blows from north to south.
The east wind blows from east to west.
The wind direction is measured in degrees clockwise, i.e. the north wind is 0 degrees, the east wind is 90 degrees.
Wind speed is the speed at which air moves in a horizontal direction.
The Beaufort scale is used for visual assessment of wind speed.
The Beaufort scale is a twelve point scale adopted by the World Meteorological Organization for approximate assessment of wind speed by its impact on land objects or by waves in the open sea.
The average wind speed is indicated at a standard height of 10 m above an open flat surface.
The wave height in the scale is given for the open ocean, not the coastal zone.
Beaufort Points
Verbal definition of wind power
Average wind speed, m / s
Average wind speed, km/h
Wind action
on land
on the sea
0
Calm
0—0,2
< 1
No wind.
The smoke rises vertically, the leaves of the trees are motionless
The mirror smooth sea
1
Quiet
0,3—1,5
1—5
The wind direction is noticeable by the smoke smell, but not by the weather vane
There are no ripples, there is no foam on the crests of the waves.
Wave height up to 0.1 m
2
Easy
1,6—3,3
6—11
The movement of the wind is felt by the face, the leaves rustle, the weather vane is set in motion
Short waves with a maximum height of up to 0.3 m, the crests do not tip over and appear glassy
3
Weak
3,4—5,4
12—19
The leaves and thin branches of the trees are constantly swaying, the wind is waving light flags
Short, well defined waves.
The ridges, tipping over, form a glassy foam.
Occasionally small lambs are formed.
The average wave height is 0.6 m
4
Moderate
5,5—7,9
20—28
The wind picks up dust and debris, sets in motion the thin branches of trees
The waves are elongated, the lambs are visible in many places.
Maximum wave height up to 1.5 m
5
Fresh
8,0—10,7
29—38
Thin tree trunks are swaying, the movement of the wind is felt by the hand
Well developed in length, but not large waves, the maximum wave height is 2.5 m, the average is 2 m.
White sheep are visible everywhere (in some cases, splashes are formed)
6
Strong
10,8—13,8
39—49
Thick branches of trees are swaying, telegraph wires are humming
Large waves begin to form.
White foamy ridges occupy significant areas, splashes are likely.
The maximum wave height is up to 4 m, the average is 3 m
7
Strong
13,9—17,1
50—61
The tree trunks are swaying
The waves pile up, the crests of the waves break, the foam lies in strips on the wind.
The maximum wave height is up to 5.5 m
8
Very strong
17,2—20,7
62—74
The wind breaks the branches of trees, it is very difficult to go against the wind
Moderately high long waves.
Splashes begin to fly up along the edges of the ridges.
The foam strips fall in rows in the direction of the wind.
The maximum wave height is up to 7.5 m, the average is 5.5 m
9
Storm
20,8—24,4
75—88
Minor damage, the wind begins to destroy the roofs of buildings
High waves (maximum height — 10 m, average 7 m).
The foam lies in wide dense strips on the wind.
The crests of the waves begin to tip over and crumble into splashes, which worsen visibility
10
A strong storm
24,5—28,4
89—102
Significant destruction of buildings, the wind uproots trees
Very high waves (maximum height — 12.5 m, average 9 m) with long crests curving downwards.
The resulting foam is blown by the wind in large flakes in the form of thick white stripes.
The surface of the sea is white with foam.
The strong roar of the waves is like blows
11
A violent storm
28,5—32,6
103—117
Large destruction over a significant area.
It is observed very rarely.
Visibility is poor.
Exceptionally high waves (maximum height up to 16 m, average 11.5 m).
Small and medium sized vessels sometimes disappear from view.
The sea is all covered with long white flakes of foam, located in the wind.
The edges of the waves are blown into foam everywhere
12
Hurricane
> 32,6
> 117
Huge destruction, buildings, buildings and houses were seriously damaged, trees were uprooted, vegetation was destroyed.
The case is very rare.
Exceptionally poor visibility.
The air is filled with foam and splashes.
The sea is all covered with strips of foam
Long term observations of the direction and strength of the wind are depicted in the form of a graph wind roses.
The wind rose is a vector diagram that characterizes the wind regime in a given place according to long term observations.
It looks like a polygon where the lengths of the rays diverging from the center of the diagram in different directions (the points of the horizon) are proportional to the repeatability of the winds of these directions ("from where" the wind blows).
Global causes of wind occurrence.
The main reason for the occurrence of wind is the difference in atmospheric pressure over parts of the Earth's surface.
It is only necessary for the pressure to decrease or increase somewhere, as the air will be directed from the place of greater pressure towards a smaller one.
Due to the continuous change of pressure in time and space, the wind speed and direction are constantly changing.
With altitude, the wind speed changes due to the decreasing friction force.
The distribution of atmospheric pressure over the earth's surface.
As already mentioned above, different atmospheric pressure prevails over different parts of the Earth's surface.
This is due to the peculiarities of heating and air movement.
Above the equator, the air warms up well.
This makes it expand, become less dense, and therefore easier.
The heated air rises up - there is an upward movement of air.
Therefore, a low pressure belt is established at the equator near the Earth's surface during the year.
Over the poles, where temperatures are low throughout the year, the air cools, becomes denser and heavier.
It descends - there is a downward movement of air and the pressure increases.
Therefore, high pressure belts were formed at the poles.
The air that has risen above the equator spreads to the poles.
But before reaching them, it cools at altitude, becomes heavier and falls at parallels 30-350 in both hemispheres.
As a result, belts of moderately high pressure are formed there.
Local causes of wind occurrence.
It should be understood that in each of the atmospheric pressure zones, this pressure itself is not a constant value.
The air temperature, and, accordingly, the pressure that it exerts on the earth's surface depends on many factors: the time of day, season, features of light absorption of heated surfaces, relief, etc.
All this is the local causes of the pressure difference on certain parts of the Earth's surface, and, accordingly, the causes of the wind.
Thermal wind and coastal breeze.
On a bright sunny day, the earth's surface is heated by the sun, and the heating occurs unevenly.
Areas such as arable land, rocky or sandy soils are heated much faster than areas covered with water or dense vegetation.
The air heated above the field goes up and is replaced by cold air, for example, a nearby lake.
At this moment, a light breeze will blow on the border of the field and the lake.
This is the thermal wind.
A similar picture is observed on the seashore.
During the day, the land heats up faster than the sea.
The air heated above the earth's surface rises up and is replaced by cold air from the sea.
The wind blows from the sea to the shore.
At night, the earth's surface cools quickly, the sea becomes warmer than the land, and the wind begins to blow from the shore into the sea.
These winds are called coastal breezes.
Their speed can reach 10 m / s.
See Figure 4.
Mountain breeze.
Mountain breezes are the result of the fact that during the day the air located near the mountain slopes warms up more than the air located further from the surface.
Warm air rises along the slopes, creating a vacuum at the bottom of the valley.
Masses of cold air from the center of the valley rush into the rarefaction zone.
A mountain rising breeze is formed.
At night, the opposite phenomenon is observed.
The air above the mountain peaks cools faster than the central column of air.
Cold air flows down the slopes, while a column of warm air in the center of the valley rises up.
A mountain descending breeze is formed.
See Figure 5.
Local winds are winds characteristic of relatively small, limited area areas.
The strength and direction of such winds is determined by the terrain features of a particular area.
These include, for example, breeze, hair dryer and bora.
We have already sorted out the breeze.
This is a warm wind blowing from the shore to the sea at night and from the sea to the shore during the day; in the first case, it is called a coastal breeze, and in the second — a sea breeze.
A hair dryer is a strong warm and dry wind blowing from the mountains to the coast or valley.
Hair dryers can be formed when the mountain system is occupied by an anticyclone, while there is a general lowering of air on both slopes of the mountain.
The warmth and dryness of the hair dryers is due to the fact that the air meets an obstacle when it moves.
The air flow is slowed down and quickly heats up, the humidity decreases.
At the same time, cold air from the slopes tends to replace the warm air of the valley and flows down.
The hair dryer blows.
This wind is most often characteristic of spring and summer.
Bora is a cold, sharp wind blowing from the mountains to the coast or valley.
It is formed more often in winter, when cold air quickly passes through low mountain ranges, and, without having time to warm up, falls down to the heated surface.
It can reach hurricane strength.
The wind is near the ground.
Wind gradient.
As mentioned earlier, the wind gradient is a change in the speed and direction of the wind with height relative to the earth's surface.
Due to the friction of moving air on the ground, the wind speed at the surface is less than at altitude.
This layer of air is called the boundary layer.
The boundary layer is a friction layer: a thin layer of air near a streamlined surface, in which the effect of viscosity (resistance to the movement of one part of a liquid or gas relative to another) is manifested.
By the way, the air layer near the surface of the aircraft is also borderline, because it has the same effects.
It should also be noted that the terrain irregularities and thermal activity turbulate the surface layers of air and sometimes change the wind direction near the ground relative to the flow at altitude.
See Figure 7.
A noticeable increase in wind speed is observed up to heights of about 300-350 meters above the ground her.
Gusts of wind.
A gust of wind is a short term increase in wind speed.
The rush does not last long, and it should not be evaluated in points on the Beaufort scale.
The influence of the streamlined surface on the air flow.
For example, there is a local braking of the air flow when passing all sorts of obstacles: houses, slopes, trees.
When flowing around these surfaces, the flow is turbolized, twists and either just a part of it suddenly begins to blow in the other direction, or suddenly "catches up" with the flowing air.
In addition, wind gusts are caused by thermal activity.
The wind, passing over the heated surface, tears off bubbles of even warmer air from it, which immediately tends to rise up.
At this moment, there is a kind of acceleration of the air mass, i.e. a gust of wind.
Global atmospheric phenomena.
Air masses
What I described above – the wind, and what I have not yet managed to describe clouds, fog, precipitation – all this is called atmospheric phenomena.
Atmospheric phenomena are a visible manifestation of complex physical and chemical processes occurring in the Earth's air envelope the atmosphere.
There is a classification of atmospheric phenomena:
Hydrometeors — a set of water droplets or ice particles floating in the air (clouds, fogs), precipitation falling from the atmosphere (rain, drizzle, snow, hail, ice rain, ice grains, snow grains, snow grains), formed on the Earth's surface and objects located on it, ground hydrometeors (dew, frost, frost (crystalline and granular), hard plaque, ice, ice), raised by the wind from the earth's surface (blizzard, pozemok);
Lithometeors are a set of solid (not water) particles that are lifted by the wind from the earth's surface and transported to a certain distance or float in the air (dust storm, dusty (sandy) snow);
Electrical phenomena — light and sound manifestations of atmospheric electricity (thunderstorm, lightning, St. Elmo's lights, ball lightning);
Optical phenomena the consequences of refraction or diffraction of sunlight or moonlight in the atmosphere (rainbow, halo, mirage, circle around the Moon, crown around the Sun, crown around the Moon, solar column, dawn, gloria);
Unclassified — various meteorological phenomena in the atmosphere that are difficult to attribute to any of the above types (squall, Dust vortex, tornado, haze, dust haze, snow haze, ice needles).
All of the above phenomena are formed as a result of the movement and interaction of air masses.
Air masses are large volumes of air in the lower part of the Earth's atmosphere the troposphere, having horizontal dimensions of many hundreds or several thousand kilometers and vertical dimensions of several kilometers, characterized by approximate uniformity of temperature and moisture content horizontally.
The uniformity of the properties of the air mass is achieved by forming it over a homogeneous underlying surface under similar conditions of thermal and radiation balance.
Air masses are classified, first of all, according to the centers of their formation, depending on their location in one of the latitudinal zones.
According to the geographical classification, air masses can be divided into the main geographical types according to the latitudinal zones in which their foci are located :
Arctic or Antarctic air (AB),
Moderate air (UV),
Tropical Air (TV),
Equatorial air (EV).
These air masses, in addition, can be divided into oceanic (m) and continental (k).
When moving, the air mass begins to change its properties — they will already depend not only on the properties of the formation center, but also on the properties of neighboring air masses, on the properties of the underlying surface over which the air mass passes, as well as on the length of time that has elapsed since the formation of the air mass.
These influences can cause changes in the moisture content in the air, as well as changes in the air temperature as a result of the release of latent heat or heat exchange with the underlying surface.
The process of changing the properties of the air mass is called transformation or evolution.
The transformation associated with the movement of the air mass is called dynamic.
The velocities of the air mass movement at different altitudes will be different, the presence of a velocity shift causes turbulent mixing.
If the lower layers of air are heated, then instability occurs and convective mixing develops (the air tends upwards).
Usually, the process of transformation of the air mass lasts from 3 to 7 days.
A sign of its end is the cessation of significant changes in air temperature from day to day, both near the earth's surface and at altitudes.
Fronts
Depending on the conditions of its occurrence, the air mass can be warm or cold.
An air mass moving over a warmer underlying surface is called cold; moving over a colder underlying surface is called warm; being in thermal equilibrium with the environment is called local.
When air masses of different temperatures come into contact in the troposphere, transitional regions arise – atmospheric fronts, their length reaches 1000 km, and their height is several hundred meters.
Thus, the atmospheric front is a transition zone in the troposphere between adjacent air masses with different physical properties.
Distinguish between:
warm fronts;
cold fronts;
occlusion fronts;
stationary fronts.
A warm front (1) is formed when warm air actively moves towards cold air.
Then the light warm air flows into the retreating wedge of cold air and rises along the interface plane.
When lifting, it cools down.
This leads to the condensation of water vapor and the appearance of cirrus and layered rain clouds, and then to precipitation.
When a warm front approaches, its harbingers appear during the day – cirrus clouds.
They float like feathers at an altitude of 7-10 km.
At this time, the atmospheric pressure decreases.
The arrival of a warm front is usually associated with warming and the fall of cold, drizzling precipitation.
A cold front (2) is formed when cold air moves towards warm air.
Cold air, as heavier, flows under the warm air and pushes it up.
At the same time, layered cumulus rain clouds arise, piling up like mountains or towers, and precipitation from them falls in the form of showers with squalls and thunderstorms.
The passage of a cold front is associated with a cooling and strengthening of the wind.
As you understand, it is the cold front that pleases the pilots.
Cyclones and anticyclones.
Wind movement in cyclones and anticyclones
Powerful air vortices are sometimes formed on the fronts, similar to whirlpools when two streams of water meet.
The dimensions of these air vortices can reach 2-3 thousand km across.
Cold air is heavier and tends to push warm air up, and warm air is lighter and tends to rise.
At the same time, the centrifugal force resulting from the rotation of the Earth twists the moving masses of air in a spiral.
When moving, the cold air begins to flow under the warm one and turns to the south, and the warm air turns to the north and flows into the cold one (the same spiral).
In the areas where warm air flows, the air pressure decreases (the molecules of warm air move faster, its pressure is lower), and in the areas where cold air flows, the air pressure increases (the molecules move slower – the pressure is higher).
As a result of the movement of cold air to the south and its rotation to the east in the direction of lowering the pressure and the movement of warm air to the north with its rotation to the west, a vortex movement occurs, moving the air to an area with low pressure.
The area of this vortex movement is called a low pressure area, or a cyclone.
So, a cyclone is an atmospheric vortex of a huge (from hundreds to several thousand kilometers) diameter with a reduced air pressure in the center.
In the central part of the cyclone, the air rises and spreads to its outskirts.
During the ascent, the air expands, cools, water vapor condenses and clouds appear.
During the passage of cyclones, cloudy weather usually occurs with rain in summer and snowfall in winter.
The wind in the cyclone moves counterclockwise in the northern hemisphere, clockwise in the southern hemisphere.
In the vertical section – from the center to the edges.
The speed of the cyclone in the direction of movement of warm air on average is 25-40 km.
If, on the contrary, the pressure is increased in the center, then this vortex is called an anticyclone.
So, an anticyclone is an area of high atmospheric pressure in the troposphere with its gradual decrease from the central part to the periphery.
In anticyclones, air outflow (wind)at the surface of the Earth, it occurs from the center to the edges, heading clockwise.
Simultaneously with the outflow of air from the anticyclone, air from the upper layers of the atmosphere enters its central part.
When it is lowered, it heats up, absorbing water vapor, and the clouds dissipate.
Therefore, in areas where anticyclones appear, clear, cloudless weather is established with weak winds, hot in summer and cold in winter.
Anticyclones cover larger areas than cyclones.
They are more stable, move at a lower speed, break down more slowly, often stay in one place for a long time.
With the approach of an anticyclone, the atmospheric pressure increases.
This attribute should be used when predicting the weather.
In addition, there are a number of other signs of an anticyclone:
Clear or low cloud weather
No wind
No precipitation
The stable nature of the weather (it does not change noticeably over time, as long as there is an anticyclone)
The barogram map.
The movement of fronts and the formation of cyclones and anticyclones can be traced on the barogram map (synoptic map) – a weather map compiled for a certain period of time.
It is compiled several times a day based on data received from a network of meteorological stations.
On this map, numbers and symbols show information about the weather – air pressure in millibars, air temperature, wind direction and speed, clouds, the position of warm and cold fronts, cyclones and anticyclones, the nature of precipitation.
The name comes from the pressure measurement units bars.
The frontal zone.
Let's go back to our air masses again.
If the air masses were stationary, the surface of the atmospheric front would be horizontal, with cold air below and warm air above it, but since both masses are moving, it is located obliquely to the earth's surface.
At the same time, the average angle of inclination is about 1° to the Earth's surface.
The cold front is inclined in the same direction in which it is moving, and the warm front is inclined in the opposite direction.
The zone of the atmospheric front is very narrow in comparison with the air masses separated by it, therefore, for the purposes of theoretical research, it is approximately considered as the interface of two air masses of different temperatures and called the frontal surface (frontal zone).
For this reason, on synoptic maps, fronts are depicted as a line (front line).
At the intersection with the earth's surface, the front zone has a width of about tens of kilometers, while the horizontal dimensions of the air masses themselves are about thousands of kilometers.
So, the frontal zone is the zone of the atmospheric front.
It is the frontal zone that interests us as a suitability or unsuitability for conducting flights.
An unstable air mass is formed in this zone.
It is characterized by the fact that in its lower layers (approximately below 3 km), unstable stratification (distribution) of the atmosphere sphere is observed.
In case of unstable stratification, the vertical temperature gradient in the air mass before the condensation level is greater than the dry adiabatic gradient, and above the condensation level more than the wet adiabatic gradient.
In an unstable air mass with sufficient humidity, convection develops (an upward movement of warm air) with the formation of vertical clouds, increased turbulence, strong gusty wind, showers, thunderstorms, squalls are observed.
A cold air mass, moving to a warmer underlying surface and warming up from below, becomes, as a rule, an unstable, stuffy mass.
A cold unstable air mass is observed most often over the mainland in the summer in the afternoon hours in the rear part of the cyclone or in the front part of the anticyclone.
The work of weather prediction services
We can predict all these movements of air masses.
For weather forecasting, maps (synoptic maps) are compared and changes in the position of warm and cold fronts, the displacement of cyclones and anticyclones and the nature of the weather in each of them are established.
Currently, space stations are widely used to refine weather predictions.
We ourselves can also predict the onset of flying or non flying weather, based on our observations.
Signs of stable and clear weather (flight weather)
The air pressure is high, almost does not change or rises slowly.
The daily course of temperature is sharply expressed: it is hot during the day, cool at night.
The wind is weak, intensifies by noon, subsides in the evening.
The sky is cloudless all day or covered with cumulus clouds that disappear in the evening.
The relative humidity of the air decreases during the day and increases by night.
During the day, the sky is bright blue, the twilight is short, the stars twinkle faintly.
In the evening, the dawn is yellow or orange.
Heavy dew or frost at night.
Fogs over the lowlands, increasing at night and disappearing during the day.
At night, it is warmer in the forest than in the field.
Smoke from chimneys and bonfires rises up.
Swallows fly high.
Signs of unstable inclement weather
The pressure fluctuates sharply or continuously decreases.
The daily temperature course is weakly expressed or with a violation of the general course (for example, the temperature rises at night).
The wind increases, sharply changes its direction, the movement of the lower layers of clouds does not coincide with the movement of the upper ones.
The cloud cover is increasing.
On the western or southwestern side of the horizon, cirrus layered clouds appear, which spread throughout the entire sky.
They are replaced by highly layered and layered rain clouds.
It's stuffy in the morning.
Cumulus clouds grow up, turning into cumulonimbus clouds to a thunderstorm.
The morning and evening dawns are red.
By nightfall, the wind does not subside, but increases.
Light circles (halos) appear around the Sun and the Moon in cirrus layered clouds.
There are crowns in the clouds of the middle tier.
There is no morning dew.
Swallows fly low.
Ants hide in anthills.
Cloud cover.
Cloud formation.
Precipitation
The air of the atmosphere always contains a certain amount of water vapor, which is formed as a result of evaporation from the surface of the land and ocean.
The rate of evaporation depends primarily on temperature and wind.
The higher the temperature and the larger the steam capacity, the stronger the evaporation.
The amount of water that can evaporate from a particular surface is called evaporation.
The evaporation rate depends on the air temperature and the amount of water vapor in it.
The higher the air temperature and the less water vapor it contains, the higher the evaporation rate.
The air can accept water vapor up to a certain limit, until it becomes saturated.
If the saturated air is heated, it will again acquire the ability to accept water vapor, i.e. it will again become unsaturated.
When the unsaturated air cools, it approaches saturation.
Thus, the ability of air to contain more or less water vapor depends on the temperature
The amount of water vapor that is contained in the air at the moment (in g per 1 m3) is called absolute humidity.
The ratio of the amount of water vapor contained in the air at a given moment to the amount that it can hold at a given temperature is called relative humidity and is measured as a percentage.
The moment of transition of air from an unsaturated state to a saturated one is called the dew point.
The lower the air temperature, the less it can contain water vapor and the higher the relative humidity.
This means that when the air is cold, the dew point occurs faster.
When the dew point occurs, i.e. when the air is completely saturated with water vapor, when the relative humidity approaches 100 %, water vapor condensation occurs – the transition of water from a gaseous state to a liquid state.
Thus, the process of condensation of water vapor occurs either with strong evaporation of moisture and saturation of the air with water vapor, or with a decrease in air temperature and relative humidity.
At negative temperatures, water vapor, bypassing the liquid state, turns into solid crystals of ice and snow.
This process is called water vapor sublimation.
Condensation and sublimation of water vapor determine the formation of precipitation.
When water vapor condenses in the atmosphere at an altitude of several tens to hundreds of meters and even kilometers, clouds form.
This occurs as a result of the evaporation of water vapor from the Earth's surface and its rise by ascending streams of warm air.
Depending on their temperature, clouds consist of water droplets or ice and snow crystals.
These droplets and crystals are so small that even weak updrafts keep them in the atmosphere.
The shape of clouds is very diverse and depends on many factors: altitude, wind speed, humidity, etc.
At the same time, it is possible to distinguish groups of clouds that are similar in shape and height.
The most famous of them are cumulus, cirrus and layered, as well as their varieties: layered cumulus, pinnately layered, layered rain, etc.
Clouds that are oversaturated with water vapor, having a dark purple or almost black hue, are called clouds.
The degree of cloud coverage of the sky, expressed in points (from 1 to 10), is called cloud cover.
A high degree of cloud cover usually portends precipitation.
Their precipitation is most likely from highly layered, cumulonimbus and layered rain clouds.
Water that has fallen in a solid or liquid state in the form of rain, snow, hail or condensed on the surface of various bodies in the form of dew, frost, is called atmospheric precipitation.
Rain is formed when the smallest droplets of moisture contained in the cloud merge into larger ones and, thus, overcome reflecting the force of the ascending air flows, they fall to the Ground under the influence of gravity.
If the smallest particles of solids, such as dust, are in the cloud, the condensation process is accelerated, since dust particles play the role of condensation nuclei.
In desert areas with low relative humidity, condensation of water vapor is possible only at high altitude, where the temperature is lower, but raindrops, not reaching the ground, evaporate in the air.
This phenomenon is called dry rains.
If the condensation of water vapor in the cloud occurs at subzero temperatures, precipitation in the form of snow is formed.
Sometimes snowflakes from the upper layers of the cloud fall into the lower part of it, where the temperature is higher and there is a huge amount of supercooled water droplets held in the cloud by ascending air currents.
Connecting with water droplets, snowflakes lose their shape, their weight increases, and they fall to the ground in the form of a snow blizzard – spherical snow lumps with a diameter of 2-3 mm.
A necessary condition for the formation of hail is the presence of a vertical development cloud, the lower edge of which is located in the zone of positive temperatures, and the upper one is in the zone of negative temperatures.
Under these conditions, the formed snow blizzard rises in ascending streams to the zone of negative temperatures, where it turns into a ball – shaped ice floe a hailstone.
The process of raising and lowering a hailstone can occur repeatedly and be accompanied by an increase in its mass and size.
Finally, the hailstone, overcoming the resistance of the ascending air currents, falls to the ground.
Precipitation such as dew, frost, fog, frost, ice, are formed not in the upper layers of the atmosphere, but in its surface layer.
Cooling from the surface of the Earth, the air can no longer hold water vapor, it condenses and settles on the surrounding objects.
This is how dew is formed.
When the temperature of objects located near the Earth's surface is below 0 °C, frost is formed.
When warmer air comes into contact with cold objects (most often wires, tree branches), frost falls – a coating of loose ice and snow crystals.
Classification of clouds
Let's linger a little on the clouds.
As I have already said, clouds come in different shapes and sizes depending on many factors: altitude, wind speed, humidity, etc.
The lowest and heaviest clouds are layered.
They are located at an altitude of 2 km from the earth's surface.
At an altitude of 2 to 8 km, you can observe more picturesque cumulus clouds (and that's exactly what we need).
The highest and lightest are cirrus clouds.
They are located at an altitude of 8 to 18 km above the Earth's surface.
Families
Genera of clouds
Appearance
A. Clouds of the upper tier above 6 km
I. Pinnate
Filamentous, fibrous, white
II.
Cirrus cumulus
Layers and ridges of small flakes and curls, white
III.
Pinnately layered
Transparent whitish veil
B. Clouds of the middle tier above 2 km
IV.
High beam
Layers and ridges of white and gray color
V. Highly layered
A smooth veil of milky gray color
B. Clouds of the lower tier up to 2 km
VI.
Layered rain
A solid shapeless gray layer
VII.
Layered cumulus
Non illuminated layers and ridges of gray color
VIII.
Layered
An impenetrable shroud of gray color
G. Vertical development clouds - from the lower to the upper tier
IX.
Cumulus
The clubs and domes are bright white in color, with torn edges in the wind
X. Cumulonimbus
Powerful cumulus like masses of dark lead color
Visibility
As I said earlier, clouds are formed as a result of condensation of water vapor in the atmosphere at a high altitude.
However, condensation can also occur at lower layers.
When water vapor is concentrated in the surface layer of the atmosphere, fog is formed.
Fogs are especially frequent in large industrial centers, where water droplets, merging with dust and gases, form a poisonous mixture – smog.
When fog is formed, visibility is significantly reduced.
Visibility is the maximum distance at which a person with normal vision can distinguish objects in daylight.
Visibility can be divided into poor (less than 3 km), normal (from 3 to 10 km) and good (over 10 km).
If the pilot from the launch site is not able to observe the site planned for landing and what is happening in the air, this significantly complicates the flight.
Therefore, for the production of flights, good visibility is necessary (over 10 km).
Flying in fog and clouds is prohibited.
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