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Geography of the planet Earth Atmosphere Weather.
What is the weather?
General information
Weather.
What is the weather?
General information
geolog March 20th, 2014 Atmosphere
Weather is a set of values of meteorological elements and atmospheric phenomena observed at a certain point in time at a particular point in space.
The concept of "Weather" refers to the current state of the atmosphere, as opposed to the concept of "Climate", which refers to the average state of the atmosphere over a long period of time.
If there are no clarifications, then the term "Weather" means the weather on Earth.
Weather phenomena occur in the troposphere (the lower part of the atmosphere) and in the hydrosphere.
The weather can be described by the pressure, temperature and humidity of the air, the strength and direction of the wind, clouds, precipitation, visibility range, atmospheric phenomena (fogs, blizzards, thunderstorms) and other meteorological elements.
The weather is experiencing continuous changes that can be very noticeable not only from one day to another, but also for even a few minutes.
Weather changes are periodic and non periodic.
Periodic changes are those changes that are periodic in nature, because they are associated with the rotation of the Earth around its axis (daily changes) or around the Sun (annual changes).
The most noticeable diurnal changes are directly at the earth's surface, due to the fact that the changes are associated with changes in the temperature of the earth's surface, and the rest of the meteorological elements are associated with the air temperature.
Annual changes are expressed in the change of seasons.
Non periodic changes, especially significant in extratropical latitudes, are caused by the transfer of air masses.
The discrepancy between the phase of periodic changes and the nature of non periodic changes leads to the most abrupt changes in the weather.
When air masses are transferred from one area of the Earth to another, they bring with them their own weather characteristics that differ from those that previously existed in this area, which change in this place in accordance with where the new air mass comes from and what properties it has in this regard.
With altitude, the intensity of non periodic weather changes generally decreases.
For aviation, it is important to take into account sharp increases in wind and turbulence, which are associated with jet currents.
Reasons
The usual weather phenomena on Earth are wind, clouds, precipitation (rain, snow, hail, etc.), fogs, thunderstorms, dust storms and blizzards.
Rarer events include natural disasters such as tornadoes and hurricanes.
Almost all weather events occur in the troposphere (the lower part of the atmosphere).
Differences in the physical properties of air masses arise due to changes in the angle of incidence of sunlight depending on the latitude and distance of the region from the oceans.
The large temperature difference between the Arctic and tropical air is the reason for the presence of high altitude jet currents.
Baric formations in the middle latitudes, such as extratropical cyclones, are formed during the development of waves in the zone of high altitude jet flow.
Since the Earth's axis is inclined relative to the plane of its orbit, the angle of incidence of the sun's rays depends on the time of year.
On average, the annual temperature on the Earth's surface varies within ±40 °C.
For hundreds of thousands of years, changes in the Earth's orbit affect the amount and distribution of solar energy on the planet, determining the long term climate.
The difference in temperatures on the surface, in turn, causes a difference in the atmospheric pressure field.
The hot surface heats the air above it, expands it, lowering the pressure and density of the air.
The resulting horizontal pressure gradient accelerates the air towards low pressure, creating wind.
And due to the work of the Coriolis effect, when the Earth rotates, the flow twists.
An example of a simple weather system is coastal breezes, and a complex one is the Hadley cell.
The atmosphere is a complex system, so minor changes in one part of it can have a big impact on the system as a whole.
In the history of mankind, there have been constant attempts to control the weather.
It has been proven that human activities, such as agriculture and industry, can influence the weather to some extent.
Precipitation formation
Clouds consist of very small water droplets or ice crystals, which are so small that they only slowly descend under the influence of gravity.
When they increase in size and become heavier, they fall faster and rain or snow falls out of the cloud.
In any cloud, water vapor is in a saturated state, that is, the largest amount of steam possible at a given temperature is contained within the cloud.
If this were not the case, the droplets that make up the cloud would evaporate and the cloud would melt.
Precipitation falls from clouds, which consist of a mixture of water droplets and ice crystals.
Due to the property of ice to attract water, the crystals gradually grow and turn into snowflakes.
This explains not only the snowfall, but also the rain.
In the troposphere, the air temperature decreases with altitude and it is always cold at an altitude of several kilometers.
Therefore, almost every summer rain begins as snow, and only when it gets into the lower warm layers, the snowflakes melt and turn into raindrops.
The air is in continuous motion, especially due to the activity of cyclones and anticyclones.
The warm air mass, which moves from warm areas to colder ones, causes an unexpected warming by its arrival.
At the same time, from contact with the colder earth's surface, the moving air mass cools from below and the air layers adjacent to the ground may be even colder than the upper layers.
The cooling of the warm air mass coming from below causes the condensation of water vapor in the lowest layers of the air, resulting in clouds and precipitation.
These clouds are located low, often fall to the ground and cause fogs.
In the lower layers of the warm air mass, it is quite warm and there are no ice crystals.
Therefore, they can not give heavy precipitation, only sometimes a fine, drizzling rain falls.
Clouds of warm air mass cover the entire sky with a smooth cover (then they are called layered) or a slightly wavy layer (then they are called layered cumulus).
The cold air mass moves from cold areas to warmer ones and brings a cold snap.
Moving to a warmer earth's surface, it is continuously heated from below.
When heated, not only does not condensation occur, but the existing clouds and fogs should evaporate, nevertheless, the sky does not become cloudless, just clouds are formed for completely different reasons.
When heated, all bodies heat up and their density decreases, so when the lowest layer of air heats up and expands, it becomes lighter and, as it were, floats up in the form of separate bubbles or jets and heavier cold air falls in its place.
Air, like any gas, heats up during compression, and cools down during expansion.
Atmospheric pressure decreases with altitude, so the air, rising, expands and cools by 1 degree for every 100 m of ascent, and as a result, condensation and cloud formation begins in it at a certain height.
The descending air jets are heated by compression and not only does nothing condense in them, but even the remnants of clouds that fall into them evaporate.
Therefore, the clouds of cold air masses are clouds piling up in height with gaps between them.
Such clouds are called cumulus or cumulonimbus clouds.
They never descend to the ground and do not turn into fogs, and, as a rule, do not cover the entire visible sky.
In such clouds, ascending air flows drag water droplets into those layers where there are always ice crystals, while the cloud loses its characteristic "cauliflower" shape and the cloud turns into a cumulonimbus.
From this moment, precipitation falls out of the cloud, although strong, but short lived due to the small size of the clouds.
Therefore, the weather of cold air masses is very unstable.
Atmospheric front
The boundary of contact of different air masses is called the atmospheric front.
On synoptic maps, this border is a line that meteorologists call the "front line".
The boundary between the warm and cold air mass is an almost horizontal surface, imperceptibly descending to the front line.
Cold air is under this surface, and warm air is on top.
Since the air masses are always in motion, the boundary between them is constantly shifting.
An interesting feature: the front line necessarily passes through the center of the low pressure area, and the front never passes through the centers of the high pressure areas.
A warm front occurs when a warm air mass moves forward and a cold one retreats.
The warm air, as a lighter one, creeps over the cold one.
Due to the fact that the rise of air leads to its cooling, clouds form above the surface of the front.
Warm air climbs up quite slowly, so the cloud cover of the warm front is a smooth veil of pinnately layered and highly layered clouds, which has a width of several hundred meters and sometimes thousands of kilometers in length.
The further ahead of the front line there are clouds, the higher and thinner they are.
A cold front is moving towards warm air.
At the same time, the cold air gets under the warm one.
The lower part of the cold front lags behind the upper part due to friction against the earth's surface, so the front surface bulges forward.
The development and movement of cyclones and anticyclones leads to the transfer of air masses over considerable distances and corresponding non periodic weather changes associated with a change in wind directions and speeds, with an increase or decrease in cloud cover.
Small scale vortices (tornadoes, blood clots, tornadoes) are also important for the weather.
A cyclone is an atmospheric vortex of a huge (from hundreds to several thousand kilometers) diameter with a reduced air pressure in the center.
There are extratropical and tropical cyclones.
The latter have special properties and occur much less often.
Tropical cyclones are formed in tropical latitudes and have smaller sizes (hundreds, rarely more than a thousand kilometers), but large baric gradients and wind speeds reaching hurricane ones.
Such cyclones are characterized by the "eye of the storm" — a central region with a diameter of 20-30 km with relatively clear and windless weather.
Tropical cyclones can turn into extratropical ones in the course of their development.
A cyclone is not just the opposite of an anticyclone, they have a different mechanism of occurrence.
Cyclones constantly and naturally appear due to the rotation of the Earth, thanks to the Coriolis force.
Studying the weather
"Meteorology (from the Greek metéros — raised up, celestial, metéra — atmospheric and celestial phenomena and ... logy), the science of the atmosphere and the processes occurring in it."
atmospheric physics is the main branch of meteorology that studies physical phenomena and processes in the atmosphere.
synoptic meteorology is the science of weather and methods of its prediction.
Weather forecast — "a scientifically based assumption about the upcoming weather changes, based on the analysis of the development of large scale atmospheric processes".
Atmospheric chemistry studies the chemical processes in the atmosphere.
Dynamic meteorology studies atmospheric processes by theoretical methods of hydroaeromechanics.
Biometeorology studies the influence of atmospheric factors on biological processes.
The World Meteorological Organization coordinates the activities of the meteorological services of various countries.
Meteorological information
There are two types of meteorological information:
the primary information about the current weather obtained as a result of meteorological observations.
weather information in the form of various summaries, synoptic maps, aerological charts, vertical sections, cloud maps, etc.
The success of the developed weather forecasts largely depends on the quality of the primary meteorological information.
The main consumers of meteorological information are aviation and the navy.
Agriculture is also highly dependent on weather conditions and climate.
The productivity is greatly influenced by the humidity of the soil and air, the amount of precipitation, light, and heat.
At the end of the XIX century, an independent branch of meteorology was formed — agrometeorology.
Climate information is widely used in the design and operation of various structures — buildings, airfields, railways, power lines, etc.
Organization of meteorological observations
In Russia, there is an extensive network of meteorological stations (of various categories with different observation programs), meteorological and hydrological posts.
A significant role is played by observations made by means of meteorological radars (spatial images of cloud layers and the intensity of precipitation and thunderstorms within a radius of up to 250 km from the location of the locator) and meteorological artificial Earth satellites (television images of clouds in various wavelength ranges, vertical profiles of temperature and humidity in the atmosphere).
Aerological observations are carried out on a network of special aerological stations with the help of radiosondes, sometimes with the help of meteorological and geophysical rockets.
Observations on the seas and oceans from specially equipped vessels.
The ground based meteorological network in the USSR reached its maximum development by the mid 1980s.
The economic crisis processes that began in the late 1980s caused a significant reduction in the meteorological network.
From 1987 to 1989, the number of weather stations in the USSR decreased by 15 %, at the beginning of 1995, the decrease in the number of weather stations in the Russian Federation was 22 %.
In the future, it is also possible to reduce weather stations due to the development of other methods of obtaining weather information (satellite and radar).
Synoptic maps
A synoptic map (Greek: συνοπτικός, "visible at the same time") is a geographical map on which the results of observations of many weather stations are marked with conventional signs.
Such a map gives a visual representation of the current state of the weather.
With the sequential compilation of maps, the directions of the movement of air masses, the development of cyclones, the movement of fronts are found out.
The analysis of synoptic maps allows you to anticipate changes in the weather.
It is possible to track changes in the state of the atmosphere, in particular, the movement and evolution of atmospheric disturbances, the movement, transformation and interaction of air masses, etc.
Since the mid 20th century, ground level synoptic information has been supplemented by the results of aerological observations, on the basis of which maps of the state of the free atmosphere are regularly built — the so called maps of baric topography.
Since the end of the 20th century, satellite information on the state of the oceans and parts of the land where there are no weather stations has also been widely used.
Photographing cloud systems from satellites allows you to detect the origin of tropical cyclones over the oceans.
Studying the weather on other planets
Weather exists not only on Earth, but also on other celestial bodies (planets and their satellites) that have an atmosphere.
Studying the weather on other planets has become useful for understanding the principles of weather changes on Earth.
A well known research object in the Solar System — the Great Red Spot of Jupiter, is an anticyclonic storm that has existed for at least 300 years.
However, the weather is not limited to planetary bodies.
The Sun's corona is constantly being lost into space, creating essentially a very thin atmosphere throughout the Solar System.
The movement of particles emitted by the Sun is called the solar wind.
Meteorological elements
Atmospheric phenomena are a visible manifestation of complex physical and chemical processes occurring in the Earth's air envelope the atmosphere:
precipitation (rain, snow, hail) fog blizzard thunderstorm tornado, etc.
Values that determine the "equivalent comfortable temperature":
atmospheric pressure air temperature air humidity wind speed and direction
Values important for transport and agriculture:
visibility range atmospheric turbulence possibility of icing solar radiation cloudiness, duration of sunshine possibility of a storm (at sea, large lake)
Weather forecasts
A weather forecast is a scientifically and technically sound assumption about the future state of the atmosphere in a certain place.
People have been trying to predict the weather for thousands of years, but official forecasts appeared in the nineteenth century.
To make a weather forecast, quantitative data on the current state of the atmosphere is collected, and with the help of a scientific understanding of atmospheric processes, it is projected how the state of the atmosphere will change.
If earlier forecasts were based mainly on changes in atmospheric pressure, current weather conditions and the state of the sky, now forecasting models are used to determine future weather.
Human participation is necessary to select the most appropriate forecasting model, on which the forecast will be based in the future.
This includes the ability to choose a model template, taking into account the relationship of remote events, knowledge of the principles of operation and features of the selected model.
The complex nature of the atmosphere, the need for powerful computer technology to solve equations describing the atmosphere, the presence of errors in measuring the initial conditions and an incomplete understanding of atmospheric processes mean that the accuracy of the forecast is reduced.
The greater the difference between the present time and the time for which the forecast is made (the forecast range), the lower the accuracy.
Using several models and bringing them to a single result helps to reduce the error and get the most likely result.
Many people use weather forecasts.
Storm warnings are important forecasts, as they are used to protect life and property.
Forecasts of temperature and precipitation are important for agriculture and, therefore, even for traders in the stock markets.
Moreover, there are even so called derivative financial instruments for the weather.
Thermal networks also need temperature forecasts to assess the heat energy needed in the coming days.
Every day, people use the weather forecast to decide what to wear on this day.
Forecasts of rain, snow and strong winds are used for planning work and outdoor recreation.
Currently there is a grid project ClimatePrediction.net the purpose of which is to find the most adequate model of climate change and build a forecast for the next 50 years on its basis.
Influence on people
Weather plays a big, and sometimes even a decisive role in human history.
In addition to climate changes that caused the gradual migration of peoples (for example, the desertification of the Middle East and the formation of land bridges between continents during ice ages), extreme weather events caused smaller scale movements of peoples and were directly involved in historical events.
One of such cases is the rescue of Japan by Kamikaze winds from the invasion of the Mongol fleet of Kublai Khan in 1281.
The French claim to Florida ended in 1565, when a hurricane destroyed the French fleet, giving Spain the opportunity to conquer Fort Carolina.
Most recently, Hurricane Katrina forced more than one million people to relocate from the central coast of the Gulf of Mexico to the United States, creating the largest diaspora in the history of the United States.
In addition to such a radical influence on people, the weather can affect a person in simpler ways.
People do not tolerate extreme values of temperature, humidity, pressure and wind.
The weather also affects mood and sleep.
The desire to influence meteorological phenomena can be traced throughout the history of mankind: from the oldest ritual rituals conducted in an attempt to summon rain to special military operations of our time, such as Operation Popeye of the American military forces during the Vietnam War (1965-1973), when attempts were made to prevent the supply of South Vietnamese guerrillas with weapons and food by extending the period of the Vietnamese monsoon.
The most successful attempts to influence the weather include cloud seeding, active influence on fogs and layered clouds in order to disperse them, used by large airports, techniques to increase snow precipitation over the mountains and reduce precipitation in the form of hail.
A recent example of the impact on hydrometeorological processes is the measures taken by China for the 2008 Summer Olympic Games.
1104 rockets were launched, with the help of which special reagents are seeded into the clouds.
Implemented by Beijing, they were intended to avoid rain during the opening ceremony of the Games on August 8.
Hu Guo, head of the Beijing City Meteorological Bureau, confirmed the success of the operation
While the effectiveness of such methods of influencing the weather has not yet been definitively proven, there is convincing evidence that agriculture and industry have an impact on the weather:
Acid rain caused by the entry of sulfur oxide and nitrogen oxides into the atmosphere has a detrimental effect on lakes, plants, and buildings.
Industrial waste (English: Human impact on the environment) worsens the quality of the air and its visibility.
Climate change caused by processes that lead to the release of greenhouse gases into the air is believed to affect the frequency of occurrence of such adverse events (Eng. Extreme weather) such as droughts, extreme temperatures, floods, storm winds and storms.
The amount of heat produced by large urban conglomerates immediately affects the weather in the region, even at distances of 1,000 miles.
The effects of unintended changes in weather conditions can pose a serious threat to many components of our civilization, including ecosystems, natural resources, economic development and human health.
Small scale meteorology
Micrometeorology, which considers meteorological phenomena of small and ultra small scales, both in time and in space, deals with atmospheric phenomena less than one kilometer, that is, those that are no longer considered by medium scale meteorology (English Mesoscale meteorology).
These two branches of meteorology are sometimes combined together, and they include the study of objects whose scales are smaller than those considered by Synoptic scale meteorology and cannot be reflected on a synoptic map.
This may include small and usually wandering clouds and similar objects.
Weather on other planets
Studying the weather features on other planets contributes to a deeper understanding of the processes occurring on Earth.
On other planets, weather conditions obey many of the physical laws inherent in the weather on Earth, but they occur on a different scale and in atmospheres different from the earth's chemical composition.
The Cassini Huygens mission to Titan discovered clouds formed from methane or ethane on the satellite, which produce rain consisting of liquid methane and other organic components.
The Earth's atmosphere consists of six zones of circulation in latitude, three in each hemisphere.
Unlike Earth, Jupiter is surrounded by many such zones.
Titan has only one stream near the 50th parallel of north latitude and one near the equator.
Weather records
Weather records are extreme meteorological indicators that have been officially registered on the Earth's surface.
The lowest temperature in history was recorded on July 21, 1983 at Vostok Station, Antarctica -89.2 °C.
The warmest recorded on September 13, 1922 in Alazizayi, Libya.
Then the thermometer rose to 58 °C; the value, however, is disputed.
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