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Meteorology

The course on meteorology deals with the atmosphere and atmospheric processes responsible for the production of different weather and climatic conditions

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The course on meteorology deals with the atmosphere and atmospheric processes responsible for the production of different weather and climatic conditions

Course Reviews

  1. Couldn’t find any material to study.Disappointed.

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  2. Interesting and valuable course on meterology
    The course was very interesting and got a valuable knowledge about defenition of meterology, branches, atmosphere. composition, aeresols,rainfall pattern over india. wind cyclones, mansoon, weather, climate ,mansoon pattern,wind pattern, clouds, lightening and thunderstorms,breeze and wind, coriolis effect

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  3. Thunder and lightening
    Thunder is the sound caused by lightning. Depending on the distance and nature of the lightning, thunder can range from a sharp, loud crack to a long, low rumble (brontide). The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within a bolt of lightning. In turn, this expansion of air creates a sonic shock wave, similar to a sonic boom, which produces the sound of thunder, often referred to as a clap, crack, or peal of thunder.
    The cause of thunder has been the subject of centuries of speculation and scientific inquiry. The first recorded theory is attributed to the Greek philosopher Aristotle in the fourth century BC, and an early speculation was that it was caused by the collision of clouds. Subsequently, numerous other theories were proposed. By the mid-19th century, the accepted theory was that lightning produced a vacuum.
    In the 20th century a consensus evolved that thunder must begin with ashock wave in the air due to the sudden thermal expansion of the plasma in the lightning channel.[1] The temperature inside the lightning channel, measured by spectral analysis, varies during its 50 μs existence, rising sharply from an initial temperature of about 20,000 K to about 30,000 K, then dropping away gradually to about 10,000 K. The average is about 20,400 K (20,100 °C; 36,300 °F).[2] This heating causes a rapid outward expansion, impacting the surrounding cooler air at a speed faster than sound would otherwise travel. The resultant outward-moving pulse is a shock wave,[3] similar in principle to the shock wave formed by an explosion, or at the front of asupersonic aircraft.
    Experimental studies of simulated lightning have produced results largely consistent with this model, though there is continued debate about the precise physical mechanisms of the process.[4][1] Other causes have also been proposed, relying on electrodynamic effects of the massive current acting on the plasma in the bolt of lightning.[5] The shockwave in thunder is sufficient to cause injury, such as internal contusion, to individuals nearby.[6]
    Inversion thunder results when lightning strikes between cloud and ground occur during a temperature inversion. In such an inversion, the air near the ground is cooler than the higher air. The sound energy is prevented from dispersing vertically as it would in a non-inversion and is thus concentrated in the near-ground layer. Inversions often occur when warm moist air passes above a cold front; the resulting thunder sound is significantly louder than it would be if heard at the same distance in a non inversion condition

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  4. Thunder clouds structure
    Figure 1 shows the electrical charge distribution inside a thundercloud in its mature stage. The positive charge is distributed widely at the top of the cloud, while the negative charge is distributed vertically, in a column.
    The precipitation area is distributed densely from around the freezing level (an altitude where the temperature is 0ºC) to heights where the temperature is minus 40ºC.
    Also, there are positive charges distributed locally near the base of the cloud.

    Electrical charge distribution in thunderclouds

    Electrical charge distribution in thunderclouds
    Figure 2 compares a model of thunderclouds observed in winter in northern Japan with a typical summer thundercloud. The figure shows how the winter thundercloud lies low at low temperature altitudes and, due to powerful north westerly seasonal winds, the cells of the thundercloud incline towards the horizontal.
    Whereas the vertical structure of the summer cells means that lightning is discharged exclusively from the negative charge in the lower part of the cloud, in the winter cells the diagonally upward positive charge tends to discharge lightning directly towards the ground. In the northern part of Japan, about half of the lightning is of this type.

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  5. Thunder storms
    Thunderstorm Basics

    What is a thunderstorm?
    A thunderstorm is a rain shower during which you hear thunder. Since thunder comes from lightning, all thunderstorms have lightning.
    Why do I sometimes hear meteorologists use the word “convection” when talking about thunderstorms?
    Usually created by surface heating, convection is upward atmospheric motion that transports whatever is in the air along with it—especially any moisture available in the air. A thunderstorm is the result of convection.
    What is a severe thunderstorm?
    A thunderstorm is classified as “severe” when it contains one or more of the following: hail one inch or greater, winds gusting in excess of 50 knots (57.5 mph), or a tornado.
    How many thunderstorms are there?
    Worldwide, there are an estimated 16 million thunderstorms each year, and at any given moment, there are roughly 2,000 thunderstorms in progress. There are about 100,000 thunderstorms each year in the U.S. alone. About 10% of these reach severe levels.
    When are thunderstorms most likely?
    Thunderstorms are most likely in the spring and summer months and during the afternoon and evening hours, but they can occur year-round and at all hours.

    Along the Gulf Coast and across the southeastern and western states, most thunderstorms occur during the afternoon. Thunderstorms frequently occur in the late afternoon and at night in the Plains states.
    What kinds of damage can thunderstorms cause?
    Many hazardous weather events are associated with thunderstorms. Under the right conditions, rainfall from thunderstorms causes flash flooding, killing more people each year than hurricanes, tornadoes or lightning. Lightning is responsible for many fires around the world each year, and causes fatalities. Hail up to the size of softballs damages cars and windows, and kills livestock caught out in the open. Strong (up to more than 120 mph) straight-line winds associated with thunderstorms knock down trees, power lines and mobile homes. Tornadoes (with winds up to about 300 mph) can destroy all but the best-built man-made structures.
    Where are severe thunderstorms most common?
    The greatest severe weather threat in the U.S. extends from Texas to southern Minnesota. But, no place in the United States is completely safe from the threat of severe weather.
    What is the difference between a Severe Thunderstorm WATCH and a Severe Thunderstorm WARNING?
    A Severe Thunderstorm WATCH is issued by the NOAA Storm Prediction Center meteorologists who are watching the weather 24/7 across the entire U.S. for weather conditions that are favorable for severe thunderstorms. A watch can cover parts of a state or several states. Watch and prepare for severe weather and stay tuned to NOAA Weather Radio to know when warnings are issued.

    A Severe Thunderstorm WARNING is issued by your local NOAA National Weather Service Forecast Office meteorologists who watch a designated area 24/7 for severe weather that has been reported by spotters or indicated by radar. Warnings mean there is a serious threat to life and property to those in the path of the storm. ACT now to find safe shelter! A warning can cover parts of counties or several counties in the path of danger.
    How does a thunderstorm form?
    Three basic ingredients are required for a thunderstorm to form: moisture, rising unstable air (air that keeps rising when given a nudge), and a lifting mechanism to provide the “nudge.”

    The sun heats the surface of the earth, which warms the air above it. If this warm surface air is forced to rise—hills or mountains, or areas where warm/cold or wet/dry air bump together can cause rising motion—it will continue to rise as long as it weighs less and stays warmer than the air around it.

    As the air rises, it transfers heat from the surface of the earth to the upper levels of the atmosphere (the process of convection). The water vapor it contains begins to cool, releases the heat, condenses and forms a cloud. The cloud eventually grows upward into areas where the temperature is below freezing.

    As a storm rises into freezing air, different types of ice particles can be created from freezing liquid drops. The ice particles can grow by condensing vapor (like frost) and by collecting smaller liquid drops that haven’t frozen yet (a state called “supercooled”). When two ice particles collide, they usually bounce off each other, but one particle can rip off a little bit of ice from the other one and grab some electric charge. Lots of these collisions build up big regions of electric charges to cause a bolt of lightning, which creates the sound waves we hear as thunder.
    The Thunderstorm Life Cycle
    Thunderstorms have three stages in their life cycle: The developing stage, the mature stage, and the dissipating stage. The developing stage of a thunderstorm is marked by a cumulus cloud that is being pushed upward by a rising column of air (updraft). The cumulus cloud soon looks like a tower (called towering cumulus) as the updraft continues to develop. There is little to no rain during this stage but occasional lightning. The thunderstorm enters the mature stage when the updraft continues to feed the storm, but precipitation begins to fall out of the storm, creating a downdraft (a column of air pushing downward). When the downdraft and rain-cooled air spreads out along the ground it forms a gust front, or a line of gusty winds. The mature stage is the most likely time for hail, heavy rain, frequent lightning, strong winds, and tornadoes. Eventually, a large amount of precipitation is produced and the updraft is overcome by the downdraft beginning the dissipating stage. At the ground, the gust front moves out a long distance from the storm and cuts off the warm moist air that was feeding the thunderstorm. Rainfall decreases in intensity, but lightning remains a danger.
    thunderstorm life cycle
    Life cycle of a thunderstorm [+]
    What does a thunderstorm look like?
    Thunderstorms can look like tall heads of cauliflower or they can have “anvils.” An anvil is the flat cloud formation at the top of the storm. An anvil forms when the updraft (warm air rising) has reached a point where the surrounding air is about the same temperature or even warmer. The cloud growth abruptly stops and flattens out to take the shape of an anvil.

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  6. weather associated with cyclones
    Cyclones typically bring rain, thunderstorms, and sometimes strong winds.
    Anticyclones typically bring calm sunny weather.

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  7. cyclone-general charateritics
    Tropical Cyclones are climatological phenomena that occur across the globe. They have certain characteristics that distinguish it from other atmospheric disturbances. These are:
    The foremost characteristic is that Tropical Cyclones are most violent, most awesome and most disastrous of all the atmospheric disturbances.

    The average speed is 120 kmph. Although it may vary from 32 kmph to 200 kmph or more. At times it reaches 400 kmph also.

    They have closed isobars. The pressure gradient is very sharp. More closely spaced isobars represents greater velocity of the storm and vice-versa. The pressure at the center is extremely low. The winds from the surrounding area are drawn towards this low-pressure core called the “eye” of the cyclone.

    Tropical cyclones develop over oceans and seas only. They are most violent and vigorous over water.
    On landfall, their velocity decreases due to friction, and as the source of energy is cut off, they dissipate soon. Thus they affect the coastal areas only.
    The movement of tropical cyclone is affected by the prevailing wind system. Normally they move from east to west under the influence of trade winds.

    They are seasonal in nature and occur during a specific period of the year only.

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  8. tropical and extratropical cyclones
    We always talk about tropical cyclones. As you are probably aware, there are other kinds of cyclones, one of the most common being extra-tropical cyclones. What are extra-tropical cyclones? How are they different from tropical cyclones?

    An extra-tropical cyclone is a low pressure system that primarily gets its energy from the temperature difference in the horizontal direction across the cyclone (known as temperature gradient in meteorology) . Extra-tropical cyclones have frontal features, i.e. they are associated with cold fronts, warm fronts, and occluded fronts. Structurally, extra-tropical cyclones are “cold-core”. “Cold-core” means that the center is colder than the surroundings at the same height in the troposphere. Extra-tropical cyclones or their associated fronts may affect Hong Kong in the cool season (Figure 1).

    figure1
    Figure 1. A cold front affected south China on 30 March 2008
    Tropical cyclones, in contrast, typically have little or no significant temperature differences across the storm. Their energy are derived from the release of heat due to cloud/rain formation from the warm moist air of the tropics. Structurally, tropical cyclones are “warm-core”. Tropical cyclones usually affect Hong Kong during the hot months (Figure 2).

    figure2
    Figure 2. Typhoon Nuri affected Hong Kong on 22 August 2008
    Often, a tropical cyclone will transform into an extra-tropical cyclone as it recurves poleward. Once in a while, an extra-tropical cyclone may lose its frontal features, develop convection near the centre of the cyclone and turn into a tropical cyclone.

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  9. Cyclones
    In meteorology, a cyclone is a large scale air mass that rotates around strong centers of low pressure in the northern hemisphere.[1][2] This is usually characterized by inward spiraling winds that rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth. Most large-scale cyclonic circulations are centered on areas of low atmospheric pressure.[3][4] The largest low-pressure systems are cold-core polar cyclones and extratropical cyclones which lie on the synoptic scale. According to the National Hurricane Center glossary, warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale.[5] Mesocyclones, tornadoes and dust devils lie within the smaller mesoscale.[6] Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the Tropical Upper Tropospheric Trough during the summer months in the Northern Hemisphere. Cyclones have also been seen on extraterrestrial planets, such as Mars and Neptune.[7][8] Cyclogenesis describes the process of cyclone formation and intensification.[9] Extratropical cyclones form as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones. These zones contract to form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, cyclones occlude as cold core systems. A cyclone’s track is guided over the course of its 2 to 6 day life cycle by the steering flow of the cancer or subtropical jet stream.

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  10. precipitataion forms
    This webpage describes the different types of precipitation and explains how they form. METAR and other frequently used abbreviations for each precipitation type are given.

    1. Rain (R, RA)- Rain is liquid precipitation that reaches the surface in the form of drops that are greater than 0.5 millimeters in diameter. The intensity of rain is determined by the accumulation over a given time. Categories of rain are light, moderate and heavy.

    2. Snow (SN, SNW, S)- Snow is an aggregate of ice crystals that form into flakes. Snow forms at temperatures below freezing. For snow to reach the earth’s surface the entire temperature profile in the troposphere needs to be at or below freezing. It can be slightly above freezing in some layers if the layer is not warm or deep enough the melt the snow flakes much. The intensity of snow is determined by the accumulation over a given time. Categories of snow are light, moderate and heavy.

    3. Snow Pellets (GS)- A snow pellet is precipitation that grows by supercooled water accreting on ice crystals or snow flakes. Snow pellets can also occur when a snowflake melts about half way then refreezes as it falls. Snow pellets have characteristics of hail, sleet and snow. With sleet (ice pellets), the snowflake almost completely melts before refreezing thus sleet has a hard ice appearance. Soft hail grows in the same way snow pellets can grow and that is ice crystals and supercooled water accreting on the surface. Snow pellets will crush and break apart when pressed. They can bounce off objects like sleet does. Snow pellets have a whiter appearance than sleet. Snow pellets have small air pockets embedded within their structure and have visual remnants of ice crystals unlike sleet. Snow pellets are typically a couple to several millimeters in size.

    4. Snow Grains (SG)- Snow grains are small grains of ice. They do not produce much accumulation and are the solid equivalent to drizzle.

    5. Ice Crystals (IC)- Also called diamond dust. They are small ice crystals that float with the wind.

    6. Sleet / Ice Pellets (PE, PL, IP, SLT)- Sleet (Ice Pellets) are frozen raindrops that strike the earth’s surface. In a sleet situation the precipitation aloft when it is first generated will be snow. The snow falls through a layer that is a little above freezing and the snow partially melts. If the snow completely melts it will be more likely to reach the earth’s surface as supercooled water instead of sleet. If the snow partially melts there will still be ice within the falling drop for water to freeze on when the drop falls into a subfreezing layer. The lowest layer of the troposphere will be below freezing in a sleet situation and deep enough to freeze drops completely. The lower boundary layer can be above freezing and sleet occur if the sleet does not have time to melt before reaching the surface.

    7. Hail (GR, A)- Hail is dense precipitation ice that is that least 5 millimeters in diameter. It forms due to ice crystals and supercooled water that freeze or stick to the embryo hail stone. Soft hail is more white and less dense since it has air bubbles. Soft hail occurs when hail grows at a temperature below freezing by ice crystals and small supercooled water and cloud droplets merging onto the hail. Hard hail occurs when liquid water drops freeze on the outer edges of the hailstone after the outer edge is above freezing. The freezing of supercooled water releases latent heat and this can result in the outer edge of the hail stone warming above freezing. Then the water refreezes creating solid ice. Hail will commonly have soft ice and hard ice layers when it is sliced open.

    8. Graupel (GS)- Graupel forms in the same way as hail except the diameter is less than 5 millimeters. It usually grows by soft hail processes.

    9. Drizzle (DZ, L)- Drizzle is liquid precipitation that reaches the surface in the form of drops that are less than 0.5 millimeters in diameter.

    10. Freezing Drizzle (FZDZ, ZL)- Freezing Drizzle is liquid precipitation that reaches the surface in the form of drops that are less than 0.5 millimeters in diameter. The drops then freeze on the earth’s surface.

    11. Freezing Rain (FZRA, ZR)- Freezing Rain is liquid precipitation that reaches the surface in the form of drops that are greater than 0.5 millimeters in diameter. The drops then freeze on the earth’s surface.

    12. Freezing Fog (FZFG)- Freezing fog is a fog composed of supercooled water drops. These drops freeze just after they wet the earth’s surface.

    13. Mixed Precipitation (MXD PCPN)- The combination of two or more winter precipitation types occurring at the same time or over a period of time at the same place

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  11. clouds and precipitations
    . Cloud Descriptions and Helpful Hints for Identification
    In 1803 a pharmacist and amateur meteorologist, Luke Howard, developed ten categories for cloud identification that are still used today. His descriptions focus on the way clouds look so with practice, anyone can learn to identify clouds. Each category is a variation on three basic cloud types under different conditions, with particular attention to the altitude and appearance of the cloud.

    Basic Cloud Shapes:
    Cumulus – heaped and puffy that usually grow upwards as well as outwards.
    Stratus – layered and flat with wide coverage.
    Cirrus – wispy, feathery tufts of clouds often characterized by curly wisps at the ends; sometimes called ‘mares tails’ because they look like horse’s tails blowing in the wind.

    Clouds occur at three altitude ranges (heights) in the sky. We judge the height of the clouds according to the base or bottom of the cloud and not the height (this is especially important for cumulus clouds).

    High Altitude Clouds:
    are above 6000 metres
    start with ‘cirro’ or ‘cirrus’
    are either:
    1. Cirrus – ‘Cirrus’ being wispy and feathery at high altitude.
    2. Cirrocumulus – ‘Cumulus’ being puffy and heaped; ‘Cirro’ meaning high altitude. Less puffy than cumulus and more wispy like cirrus, but with definite bumps and ripples. The sun is visible through them.

    3. Cirrostratus – ‘Stratus’ being flat layers of clouds and ‘Cirro” being high altitude; the layers are wispy and form a thin veil of coverage over all or part of the sky through which you can see the sun.

    Middle Altitude Clouds:
    are between 2000 and 6000 metres
    start with ‘alto’
    are either:
    4. Altocumulus – ‘Cumulus’ being puffy and heaped, but less dense in appearance than cumulus in a rippled pattern. There are also more spaces in the clouds so the sun is visible through them.
    5. Altostratus – ‘Stratus’ being flat layers of formless, shapeless clouds. The sun is visible through this sheet of clouds that can cover part of the sky or the full sky from horizon to horizon.
    NOTE: there are no middle range clouds with the prefix ‘cirrus’ or ‘cirro’ because Cirrus clouds are synonymous with high altitude clouds.
    Low Altitude Clouds:

    are below 2000 metres
    have no prefix
    are either:
    6. Stratus – Flat layered clouds, usually dull grey, which cover most of the sky, even blocking out the sun. They begin as a bank of fog that has risen higher than ground level.
    7. Nimbostratus – ‘Stratus’ meaning broad layers covering the whole sky, and ‘Nimbo’ meaning that they are producing steady, long lasting, though not heavy, rain that covers a broad area. They are dark grey clouds that usually mean a dull day and possibly rain. They completely block out the sun.
    8. Cumulus – Meaning puffy and heaped.
    9. Stratocumulus – Meaning they are basically a flat sheet of clouds covering most, if not all of the sky, but “cumulus’ meaning that the layer is somewhat puffy.
    10. Cumulonimbus – ‘Cumulo’ meaning puffy, and ‘nimbus’ meaning there is precipitation falling from them. Characterized by dark bases and puffy tops, heavy rain, and thunder and lightening.
    Any low altitude clouds that are dark, threatening rain or producing rain get the designation ‘nimbus’ or ‘nimbo’.

    Cumulus and Cumulonimbus clouds have a base that starts at less than 2000 metres, but often grow tall enough to reach into the middle and sometimes high ranges. Only cirrus-type clouds are true high altitude clouds. They a base starting above 6000 meters.

    Extended Notes About Cloud Shapes:

    Cumulus means a heap or pile in Latin. These are white puffy clouds that look like giant bunches of cauliflower with flat bottoms. They are seen mainly in the summer on warm, sunny days. The sun warms the ground and huge bubbles of heated air rise into the sky. As with other clouds, the air cools, condenses, and in this case forms a cloud that is big and fluffy looking due to the cloud being formed with liquid versus ice crystals.

    Cumulus clouds reflect sunlight well because of the water droplets and they look very white. They are darker on the bottom because the sunlight gets filtered out more and more as it passes through these thick clouds, especially when they are at their largest. We generally don’t see these in winter because it is too cold for the droplets to remain unfrozen.

    Cirrus means a curl or a tuft of hair (wispy) in Latin. These are feathery, wispy clouds with curled tails, like a horse’s tail blowing in the wind. These are high-altitude clouds made the same way that all clouds form, but the water droplets are frozen to form millions of tiny ice crystals. They are often the first clouds to appear in a clear, blue sky.

    Stratus means a flat layer or ‘stretched out’ in Latin. These are dull grey clouds. They cover most of the sky and block out direct views of the sun. They often start as a bank of fog (low dense cloud) that rises higher in the sky.

    How Do Clouds Form?
    For more detail on weather fronts, see the sections:

    Climate

    References

    Clouds occur at weather fronts. Weather fronts occur where warm and cold air masses meet.

    Warm air is pushed higher and as it rises and cools, this causes condensation, which forms clouds. Clouds, mist and fog are made of millions of water droplets of condensing moisture from the air. They can also be made of tiny ice crystals that form as a result of the cooling process happening more quickly, or to lower surrounding temperatures.

    Rain and snow, as well as freezing rain and hail are variations of the precipitation that falls from clouds depending on the conditions in which they form. The conditions are influenced by the geographic location, weather fronts, climate, season of the year, amount of moisture in the air that results in the daily temperature, and the occurrence, amount, and form of precipitation.

    Fog is a cloud up close. It forms close to the ground as a result of air currents and fronts. A cloud is exactly the same as the white puffs of air that we see when we breathe outside on a cold day. The warm air from our lungs contacts the cold air and condenses into water droplets, forming the visible white cloud of condensed air. The same is true of water vapor (the gas form of water once heated to the boiling point) as it escapes a pot of boiling water. The air in the room is cooler than the temperature in the pot and as the warm vapor hits the cooler air, it cools, condenses and forms what we call steam, which is a cloud.

    The most important factor that must exist to form a cloud is the amount of moisture in the atmosphere. If there is not enough water in the atmosphere then there can be no condensation into tiny droplets that form clouds. The water in the atmosphere comes from oceans, lakes and plants through the water cycle. Water in lakes and oceans evaporates, just as water left in a bowl for a period of time will eventually disappear. Water that plants draw up through their roots eventually evaporates through the leaves of the plants.

    It evaporates, rising as a gas into the atmosphere, but condensing as it begins to cool in higher altitudes to form clouds. The water droplets grow larger as more warm air condenses and eventually become too heavy to continue rising or to be held up by the rising warm air. At this point the water droplets fall in the form of precipitation.

    Forms of Precipitation
    Water is part of a cycle called the Water Cycle. As water evaporates from the various bodies of water, plants, and animals, it rises into the atmosphere. There, some of the water rises high enough to cool at the higher altitude, which causes the water vapor to condense into tiny water droplets that form clouds. Some clouds produce precipitation, during which the water that forms the clouds falls back to the earth.

    Precipitation is in different forms depending on the altitude of the cloud. The altitude affects the temperature in the atmosphere and therefore the form of the water droplets that form the clouds. Another influence on the type of precipitation that forms is whether there are strong upward drafts of air inside the cloud.

    Rain is a water droplet in liquid form, usually in lower altitude clouds.

    Snow falls when clouds are in higher and colder altitudes, which causes the water vapor to freeze as it condenses to form ice crystals instead of water droplets that form the cloud.

    Sleet is rain that freezes as it is falling in cold temperatures.

    Freezing Rain is rain that freezes when it contacts the ground.

    Hail forms inside tall clouds with air currents blowing the water droplets up and down. Rain starts to fall inside the cloud, but it is caught by an upward sweeping wind and forced into a higher altitude. The drop of rain freezes in the higher altitude and falls, forming more condensation on it. It can be swept up again to refreeze, forming a larger hailstone. The size of the hailstone depends on the number of times this cycle repeats, which depends on the strength of the upward draft of wind in the cloud.

    Climate | Weather Watching | Avalanches | The Sun
    Clouds and Precipitation | Wind

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  12. local winds over different regions
    Local winds occur on a small spatial scale, their horizontal dimensions typically several tens to a few hundreds of kilometres. They also tend to be short-lived lasting typically several hours to a day. There are many such winds around the world, some of them cold, some warm, some wet, some dry. There are many hazards associated with the winds.

    The main types of local winds are:
    Sea breezes and land breezes, Anabatic and katabatic winds, and Foehn winds.

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  13. Sea breeze...winds
    Land and Sea Breezes

    As the names suggest, the two breezes occur along coastal areas or areas with adjacent large water bodies. Water and land have different heating abilities. Water takes a bit more time to warm up and is able to retain the heat longer than land does.

    Now let us see the two diagrams below:
    what is sea breeze
    In the day, when the sun is up, the land heats up very quickly and the air above it warms up a lot more than the air over the water. The warm air over the land is less dense and begins to rise. Low pressure is created.

    The air pressure over the water is higher with cold dense air, which moves to occupy the space created over the land. The cool air that comes along is called a sea breeze.
    What is land breeze

    In the night, the reverse happens. The land quickly loses its’ heat whiles the water retains its’ warmth. This means the air over the water is warmer, less dense and begins to rise. Low pressure is created over the water. Cold and dense air over the land begins to move to the water surface to replace the warmer rising air. The cool breeze from the land is called a land breeze.

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  14. Rain fall pattern over india
    Rainfall Over the country as a whole
    All India monthly, seasonal and annual rainfall series were constructed based
    on the area weighted rainfall of all the 36 meteorological subdivisions of the country.
    The results are given in Table 1. The mean, standard deviation and coefficient of
    variation are also given in the same Table. Mean (1901-2003) rainfall of July is 286.5
    mm, which is the highest and contributes 24.2 % of annual rainfall (1182.8 mm). The
    August rainfall is slightly lower and it contributes 21.2% of annual rainfall. June and
    September rainfall are almost similar and they contributes 13.8 % and 14.2 % of
    annual rainfall respectively. The mean south-west monsoon rainfall (877.2 mm)
    contributes 74.2 % of annual rainfall (1182.8 mm). Contribution of pre-monsoon
    rainfall and post-monsoon rainfall in annual rainfall is mostly the same (11%).
    Coefficient of variation is higher during the months of November, December, January
    and February. Fig.3 shows the comparison of the IITM southwest monsoon season
    (June-September) rainfall series with the rainfall series constructed in this study. The
    correlation coefficient between these two series is found to be very large, 0.97. The
    mean seasonal rainfall of IITM series is 844.5 mm whereas the men value of this
    time series is 877.2 mm. The high mean value of the present series is because of
    the consideration all the 36 meteorological subdivisions, including hilly regions. The
    standard deviation and coefficient of variability for the IITM series are 81.0 mm and
    9.6% and the same for the present time series are 71.0 mm, 8.1% respectively.
    Coefficient of variation of the present time series is smaller compared to IITM time
    series.

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  15. Rain fall pattern over india
    Rainfall is the important element of Indian economy. Although the monsoons effect most part of India, the amount of rainfall varies from heavy to scanty on different parts. There is great regional and temporal variation in the distribution of rainfall. Over 80% of the annual rainfall is received in the four rainy months of June to September. The average annual rainfall is about 125 cm, but it has great spatial variations.

    Areas of Heavy Rainfall (Over 200cm) : The highest rainfall occurs in west costs, on the western Ghats as well as the Sub-Himalayan areas in North East and Meghalaya Hills. Assam, West Bengal, West Coast and Southern slopes of eastern Himalayas.
    Areas of Moderately Heavy Rainfall (100-200 cm) : This rainfall occurs in Southern Parts of Gujarat, East Tamil Nadu, North-eastern Peninsular, Western Ghats, eastern Maharashtra, Madhya Pradesh, Orrisa, the middle Ganga valley.
    Areas of Less Rainfall (50-100 cm) : Upper Ganga valley, eastern Rajasthan, Punjab, Southern Plateau of Karnataka, Andhra Pradessh and Tamil Nadu.
    Areas of Scanty Rainfall (Less than 50 cm) : Northern part of Kashmir, Western Rajasthan, Punjab and Deccan Plateau. The two significant features of India’s rainfall is that
    i. in the north India, rainfall decreases westwards and ii. in Peninsular India, except Tamil Nadu, it decreases eastward.

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  16. Indian mansoon
    Indian monsoon,
    monsoon [Credit: Sunnyoraish]the most prominent of the world’s monsoon systems, which primarily affects India and its surrounding water bodies. It blows from the northeast during cooler months and reverses direction to blow from the southwest during the warmest months of the year. This process brings large amounts of rainfall to the region during June and July.

    At the Equator the area near India is unique in that dominant or frequent westerly winds occur at the surface almost constantly throughout the year; the surface easterlies reach only to latitudes near 20° N in February, and even then they have a very strong northerly component. They soon retreat northward, and drastic changes take place in the upper-air circulation (see climate: Jet streams). This is a time of transition between the end of one monsoon and the beginning of the next. Late in March the high-sun season reaches the Equator and moves farther north. With it go atmospheric instability, convectional (that is, rising and turbulent) clouds, and rain. The westerly subtropical jet stream still controls the flow of air across northern India, and the surface winds are northeasterlies

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  17. coriolis effect
    Coriolis effect

    The coriolis effect in action
    The Coriolis effect causes a deflection in global wind patterns. The anticlockwise rotation of the Earth deflects winds to the right in the northern hemisphere and to the left in the southern hemisphere.

    What is the Coriolis effect?
    The Earth’s rotation means that we experience an apparent force known as the Coriolis force. This deflects the direction of the wind to the right in the northern hemisphere and to the left in the southern hemisphere. This is why the wind-flow around low- and high-pressure systems circulates in opposing directions in each hemisphere.

    The Coriolis effect was described by the 19th-century French physicist and mathematician Gustave-Gaspard de Coriolis in 1835. He formulated theories of fluid dynamics through studying waterwheels, and realized the same theories could be applied to the motion of fluids on the surface of the Earth.

    The Coriolis effect in action
    One of the most common examples of the Coriolis effect in action is seen through the deflection of winds on Earth.

    Coriolis effect animation by Hubi via Wikimedia Commons
    Coriolis effect animation by Hubi via Wikimedia Commons
    Another example of the Coriolis effect can be demonstrated by looking at a typical playground roundabout. If you are standing in the centre of a spinning roundabout (spinning anticlockwise) and attempt to throw a ball, it will appear to curve to the right, when in fact it is travelling in a straight line to anyone watching who is not on the roundabout. This is similar to what happens in the northern hemisphere of the Earth, where winds are deflected to the right.

    This deflection is a major factor in explaining why winds blow anticlockwise around low pressure and clockwise around high pressure in the northern hemisphere and visa versa in the southern hemisphere. Without the Coriolis effect air would simply flow directly from areas of high pressure to areas of low pressure.

    The Coriolis effect influences the global wind patterns and gives the UK is prevailing south-westerlies. Here, winds blowing from the subtropical highs towards the low pressure in the north get deflected to the right.

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  18. effects of earths rotation on wind
    How Does Earth’s Spinning Affect Wind And Ocean Patterns?

    If Earth did not rotate on its axis, winds would blow from the north toward the south and from the south toward the north. A straight line, as drawn from the equator towards the north pole or from the north pole to the equator, as indicated in the example to the left, models this kind of wind direction.

    As you probably already know, the earth rotates on its axis from west to east. This rotation causes both the wind and ocean currents to move from east to west. Thus, the wind movement and ocean currents in the northern hemisphere goes clockwise and counter clockwise in the southern hemisphere.

    Because Earth rotates on its axis from west towards the east, air near the surface from the tropics is moved toward a westerly direction (toward the right as it is often called) in the northern hemisphere.

    Notice the difference between the lines drawn when the globe did not move (shown with arrow heads) and the lines which were drawn as Earth rotated.

    The Coriolis Effect also causes ocean surface currents to be deflected to the right of the winds. At the equator, there is no Coriolis Effect so there is very little to no deflection. At other latitudes, each layer of water (depth) is set into motion by the Coriolis Effect. Each layer moves at different velocities and moves to the right until (if you were to look from above), a spiral shape of ocean currents would form. View a QuickTime video modeling the effect of the Coriolis Effect.

    As seen in the diagram at the right, adding each of these directions together produces a net current of flow which is perpendicular to the wind (within about the top 100 meters of ocean water). This phenomenon causes currents in the northern hemisphere to move in a clockwise direction and a counterclockwise direction in the southern hemisphere. If there were no continents or island land masses, each of the ocean currents would have either an easterly or westerly flow. However, landmasses interupt the flow of ocean currents creating closed circular current systems called gyres. The five major gyres are; the North Pacific Gyre, the South Pacific Gyre, the North Atlantic Gyre, the South Atlantic Gyre, and the Indian Ocean Gyre. The parts of all gyres closest to the equator move toward the west as equatorial currents. As these gyres encounter landmasses, they are deflected toward the poles. These gyres carry warm ocean water toward cooler regions, affecting not only ocean water, but the air temperatures as well. These warm currents such as the Gulf Stream, and the Japanese Current help to moderate the weather, keeping air temperatures warmer. A prime example of this can be found along the western coasts of Great Britian. Warm Gulf Stream Water from the Gulf of Mexico helps to keep the climate more moderate. Compare the same latitude to that of central Canada.

    In addition to surface currents, water also moves vertically as deeper water rises toward shallower depths. This is referred to as Upwelling. Upwelling can occur during a La Nina event where warmer surface waters and air temperatures are blown from the western coasts of South America toward Indonesia and Australia. Deeper water from below rises toward the surface, replacing the horizontally moving water. The upwelling water is cooler and nutrient rich, causing a decrease in air temperatures near the surface.

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  19. Atmospheric pressure
    Atmospheric Pressure: Measurement, Distribution and Controlling Factors
    by P Tiwari Atmosphere
    Since air has mass, it also has weight. The pressure of air at a given place is defined as a force exerted in all directions by virtue of the weight of all the air above it. Since air pressure is proportional to density as well as temperature, it follows that a change in either temperature or density will cause a corresponding change in the pressure. The following equation called ‘the gas law’, describes the relationship between pressure, temperature and density—
    Pressure = Density x Temperature x Constant
    According to the gas law, an increase in either density or temperature will cause an increase in pressure, provided the other variable (density or temperature) remains constant.
    The atmosphere exerts a pressure of 1034 gm per square cm at sea level. This amount of pressure is exerted by the atmosphere at sea level on all animals, plants, rocks, etc.
    Measurement of Air Pressure:
    Atmospheric pressure is the weight of the column of air at any given place and time. It is measured by means of an instrument called barometer. The units used by meteorologists for this purpose are called millibars (mb). One millibar is equal to the force of one gram on a square centimetre.
    A pressure of 1000 millibars is equal to the weight of 1.053 kilograms per square centimetre. In other words, it will be equal to the weight of a column of mercury 75 cm high. The normal pressure at sea level is taken to be about 76 centimetres (1013.25 millibars). It may, however, fluctuate on either side of this value.
    The distribution of atmospheric pressure is shown on a map by isobars. An isobar is an imaginary line drawn through places having equal atmospheric pressure reduced to sea level. The spacing of isobars expresses the rate and direction of pressure changes and is referred to as pressure gradient.
    Close spacing of isobars indicates a steep or strong pressure gradient, while wide spacing suggests weak gradient. The pressure gradient may thus be defined as the decrease in pressure per unit distance in the direction in which the pressure decreases most rapidly.
    The actual direction of pressure change is always perpendicular to the isobar lines. (Fig. 2.11). A rising pressure indicates fine, settled weather, while a falling pressure indicates unstable and cloudy weather.

    Distribution of Atmospheric Pressure:
    The distribution of atmospheric pressure is not uniform over the earth’s surface. It varies vertically as well as horizontally.
    Vertical Distribution:
    Air being a mixture of gases is highly compressible. Its density is, therefore, greatest at the lower layers, where it is compressed under the mass of air above. As a result, the lower layers of the atmosphere have high density and high pressure. In contrast, the higher layers are less compressed and hence have low density and low pressure. The higher we go, the thinner the atmosphere becomes, and thus the molecules are more diffused, and there is less pressure because inter-molecular space is greater.
    At the height of Mt. Everest, the air pressure is about two-thirds less than what it is at the sea level. The decrease in pressure with altitude, however, is not constant. Since the factors controlling air density—temperature, amount of water vapour and gravity are variable, there is no simple relationship between altitude and pressure. In general, the atmospheric pressure decreases on an average at the rate of about 34 millibars every 300 metres of height.
    Horizontal Distribution:
    The distribution of atmospheric pressure across the latitudes is termed as global horizontal distribution. This distribution is characterised by presence of distinctly identifiable zones of homogeneous pressure regimes or ‘pressure belts’. On the earth’s surface, there are in all seven pressure belts.
    The seven pressure belts are: equatorial low, the sub-tropical highs, the sub-polar lows, and the polar highs. Except the equatorial low, all others form matching pairs in the northern and southern hemispheres.
    A low-pressure area, low or depression, is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in the upper levels of the troposphere. The formation process of a low-pressure area is known as cyclogenesis. Within the field of meteorology, atmospheric divergence aloft occurs in two areas. The first area is on the east side of upper troughs which form half of a Rossby wave within the Westerlies (a trough with large wavelength which extends through the troposphere). A second area of wind divergence aloft occurs ahead ofembedded shortwave troughs which are of smaller wavelength. Diverging winds aloft ahead of these troughs cause atmospheric lift within the troposphere below, which lowers surface pressures as upward motion partially counteracts the force of gravity.
    A high-pressure area, high or anticyclone is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment.
    Winds within high-pressure areas flow outward from the higher pressure areas near their centers towards the lower pressure areas further from their centers. Gravity adds to the forces causing this general movement, because the higher pressure compresses the column of air near the center of the area into greater density – and so greater weight compared to lower pressure, lower density, and lower weight of the air outside the center.
    However, because the planet is rotating underneath the atmosphere, and frictional forces arise as the planetary surface drags some atmosphere with it, the air flow from center to periphery is not direct, but is twisted due to the Coriolis effect, or the merely apparent force that arise when the observer is in a rotating frame of reference. Viewed from above this twist in wind direction is in the same direction as the rotation of the planet.
    The strongest high-pressure areas are associated with cold air masses which push away out of polar regions during the winter when there is less sun to warm neighboring regions. These Highs change character and weaken once they move further over relatively warmer water bodies.

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  20. Tornados
    What is a tornado?
    A tornado is a violently rotating column of air which descends from a thunderstorm to the ground. No other weather phenomenon can match the fury and destructive power of tornadoes. Tornadoes can be strong enough to destroy large buildings, leaving only the bare concrete foundation. In addition, they can lift 20-ton railroad cars from their tracks and they can drive straw and blades of grass into tree and telephone poles.

    How do tornadoes form?
    The truth is that scientists don’t fully understand how tornadoes form. Typically, tornadoes develop several thousand feet above the earth’s surface inside of a severe rotating thunderstorm. This type of storm is called a supercell thunderstorm. The spinning of these supercell thunderstorms is visible via Doppler radar.

    What is a supercell thunderstorm?
    A supercell is an organized thunderstorm that contains a very strong, rotating updraft. This rotation helps to produce severe weather events such as large hail, strong downbursts, and tornadoes. Supercell storms are usually isolated from other thunderstorms because it allows them to have more energy and moisture from miles around. These storms are rare, but always a threat to life and property.

    What is the difference between a funnel cloud and a tornado?
    A tornado begins as a rotating, funnel-shaped cloud extending from a thunderstorm cloud base. A funnel cloud is made visible by cloud droplets, however, in some cases it can appear to be invisible due to lack of moisture. When the funnel cloud is half-way between the cloud base and the ground, it is called a tornado. The tornado’s high-speed winds rotate about a small, relatively calm center, and suck up dust and debris, making the tornado darker and more easily seen.

    What is the path length of tornadoes? How long do they last? How fast do they move?
    Tornado paths range from 100 yards to 2.6 miles wide and are rarely more than 15 miles long. They can last from several seconds to more than an hour, however, most don’t exceed 10 minutes. Most tornadoes travel from the southwest to northeast with an average speed of 30 mph, but the speed has been observed to range from almost no motion to 70 mph.

    When and where do tornadoes occur?
    Most tornadoes occur in the deep south and in the broad, relatively flat basin between the Rockies and the Appalachians, but no state is immune. Peak months of tornado activity in the U.S. are April, May, and June. However, tornadoes have occurred in every month and at all times of the day or night. A typical time of occurrence is on an unseasonably warm and sultry Spring afternoon between 3 p.m. and 9 p.m.

    What causes tornadoes?
    Tornadoes form under a certain set of weather conditions in which three very different types of air come together in a certain way. Near the ground lies a layer of warm and humid air, along with strong south winds. Colder air and strong west or southwest winds lie in the upper atmosphere. Temperature and moisture differences between the surface and the upper levels create what we call instability. A necessary ingredient for tornado formation. The change in wind speed and direction with height is known as wind shear. This wind shear is linked to the eventual development of rotation from which a tornado may form.

    A third layer of hot dry air becomes established between the warm moist air at low levels and the cool dry air aloft. This hot layer acts as a cap and allows the warm air underneath to warm further…making the air even more unstable. Things start to happen when a storm system aloft moves east and begins to lift the various layers. Through this lifting process the cap is removed, thereby setting the stage for explosive thunderstorm development as strong updrafts develop. Complex interactions between the updraft and the surrounding winds may cause the updraft to begin rotating-and a tornado is born.

    The Great Plains of the Central United States are uniquely suited to bring all of these ingredients together, and so have become known as “Tornado Alley.” The main factors are the Rocky Mountains to the west, the Gulf of Mexico to the south, and a terrain that slopes downward from west to east.

    During the spring and summer months southerly winds prevail across the plains. At the origin of those south winds lie the warm waters of the Gulf of Mexico, which provide plenty of warm, humid air needed to fuel severe thunderstorm development. Hot dry air forms over the higher elevations to the west, and becomes the cap as it spreads eastward over the moist Gulf air. Where the dry air and the Gulf air meet near the ground, a boundary known as a dry line forms to the west of Oklahoma. A storm system moving out of the southern Rockies may push the dry line eastward, with severe thunderstorms and tornadoes forming along the dry line or in the moist air just ahead of it.

    What is the Fujita Tornado Damage Scale?
    Dr. T. Theodore Fujita, a pioneer in the study of tornadoes and severe thunderstorm phenomena, developed the Fujita Tornado Damage Scale (F-Scale) to provide estimates of tornado strength based on damage surveys. Since it is extremely difficult to make direct measurements of tornado winds, an estimate of the winds based on damage is the best way to classify them. The new Enhanced Fujita Scale (EF-Scale) addresses some of the limitations identified by meteorologists and engineers since the introduction of the Fujita Scale in 1971. Variability in the quality of construction and different local building codes made classifying tornadoes in a uniform manner difficult. In many cases, these inconsistencies led to overestimates in the strength of tornadoes. The new scale identifies 28 different free standing structures most affected by tornadoes taking into account construction quality and maintenance. The range of tornado intensities remains as before, zero to five, with ‘EF0’ being the weakest, associated with very little damage and ‘EF5’ representing complete destruction, which was the case in Greensburg, Kansas on May 4th, 2007, the first tornado classified as ‘EF5’. The EF scale was adopted on February 1, 2007.

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  21. temperature and ionic classification of atmosphere
    Atmospheric Structure

    The gaseous area surrounding the planet is divided into several concentric strata or layers. About 99% of the total atmospheric mass is concentrated in the first 20 miles (32 km) above Earth’s surface. Historical outline on the discovery of atmospheric structure.
    THERMAL STRUCTURE

    Atmospheric layers are characterized by variations in temperature resulting primarily from the absorption of solar radiation; visible light at the surface, near ultraviolet radiation in the middle atmosphere, and far ultraviolet radiation in the upper atmosphere.

    Troposphere

    The troposphere is the atmospheric layer closest to the planet and contains the largest percentage (around 80%) of the mass of the total atmosphere. Temperature and water vapor content in the troposphere decrease rapidly with altitude. Water vapor plays a major role in regulating air temperature because it absorbs solar energy and thermal radiation from the planet’s surface. The troposphere contains 99 % of the water vapor in the atmosphere. Water vapor concentrations vary with latitude. They are greatest above the tropics, where they may be as high as 3 %, and decrease toward the polar regions.
    All weather phenomena occur within the troposphere, although turbulence may extend into the lower portion of the stratosphere. Troposphere means “region of mixing” and is so named because of vigorous convective air currents within the layer.

    The upper boundary of the layer, known as the tropopause, ranges in height from 5 miles (8 km) near the poles up to 11 miles (18 km) above the equator. Its height also varies with the seasons; highest in the summer and lowest in the winter.

    Stratosphere

    The stratosphere is the second major strata of air in the atmosphere. It extends above the tropopause to an altitude of about 30 miles (50 km) above the planet’s surface. The air temperature in the stratosphere remains relatively constant up to an altitude of 15 miles (25 km). Then it increases gradually to up to the stratopause. Because the air temperature in the stratosphere increases with altitude, it does not cause convection and has a stabilizing effect on atmospheric conditions in the region. Ozone plays the major role in regulating the thermal regime of the stratosphere, as water vapor content within the layer is very low. Temperature increases with ozone concentration. Solar energy is converted to kinetic energy when ozone molecules absorb ultraviolet radiation, resulting in heating of the stratosphere.
    The ozone layer is centered at an altitude between 10-15 miles (15-25 km). Approximately 90 % of the ozone in the atmosphere resides in the stratosphere. Ozone concentration in the this region is about 10 parts per million by volume (ppmv) as compared to approximately 0.04 ppmv in the troposphere. Ozone absorbs the bulk of solar ultraviolet radiation in wavelengths from 290 nm – 320 nm (UV-B radiation). These wavelengths are harmful to life because they can be absorbed by the nucleic acid in cells. Increased penetration of ultraviolet radiation to the planet’s surface would damage plant life and have harmful environmental consequences. Appreciably large amounts of solar ultraviolet radiation would result in a host of biological effects, such as a dramatic increase in cancers.

    A popular pastime of late seems to be sending things up on balloons into the stratosphere and posting the video on YouTube
    A beer can goes to 90,000 feet altitude (17 miles, 27 km) and lands in the “drink”
    A toy robot, a Lego Space Shuttle, a Thomas the Train toy, and even an armchair
    A human goes to 128,000 feet (24+ miles, 39 km) and jumps breaking the sound barrier as he falls
    A balloon is for fine tourists, but try a rocket to get there in a hurry!

    Mesosphere

    The mesosphere a layer extending from approximately 30 to 50 miles (50 to 85 km) above the surface, is characterized by decreasing temperatures. The coldest temperatures in Earth’s atmosphere occur at the top of this layer, the mesopause, especially in the summer near the pole. The mesosphere has sometimes jocularly been referred to as the “ignorosphere” because it had been probably the least studied of the atmospheric layers. The stratosphere and mesosphere together are sometimes referred to as the middle atmosphere.
    Thermosphere

    The thermosphere is located above the mesosphere. The temperature in the thermosphere generally increases with altitude reaching 600 to 3000 F (600-2000 K) depending on solar activity. This increase in temperature is due to the absorption of intense solar radiation by the limited amount of remaining molecular oxygen. At this extreme altitude gas molecules are widely separated. Above 60 miles (100 km) from Earth’s surface the chemical composition of air becomes strongly dependent on altitude and the atmosphere becomes enriched with lighter gases (atomic oxygen, helium and hydrogen). Also at 60 miles (100 km) altitude, Earth’s atmosphere becomes too thin to support aircraft and vehicles need to travel at orbital velocities to stay aloft. This demarcation between aeronautics and astronautics is known as the Karman Line. Above about 100 miles (160 km) altitude the major atmospheric component becomes atomic oxygen. At very high altitudes, the residual gases begin to stratify according to molecular mass, because of gravitational separation.
    Exosphere

    The exosphere is the most distant atmospheric region from Earth’s surface. In the exosphere, an upward travelling molecule can escape to space (if it is moving fast enough) or be pulled back to Earth by gravity (if it isn’t) with little probability of colliding with another molecule. The altitude of its lower boundary, known as the thermopause or exobase, ranges from about 150 to 300 miles (250-500 km) depending on solar activity. The upper boundary can be defined theoretically by the altitude (about 120,000 miles, half the distance to the Moon) at which the influence of solar radiation pressure on atomic hydrogen velocities exceeds that of the Earth’s gravitational pull. The exosphere observable from space as the geocorona is seen to extend to at least 60,000 miles from the surface of the Earth. The exosphere is a transitional zone between Earth’s atmosphere and interplanetary space.

    MAGNETO-ELECTRONIC STRUCTURE

    The upper atmosphere is also divided into regions based on the behavior and number of free electrons and other charged particles.

    Ionosphere

    The ionosphere is defined by atmospheric effects on radiowave propagation as a result of the presence and variation in concentration of free electrons in the atmosphere.
    D-region is about 35 to 55 miles (60 – 90 km) in altitude but disappears at night.
    E-region is about 55 to 90 miles (90 – 140 km) in altitude.
    F-region is above 90 miles (140 km) in atitude. During the day it has two regions known as the F1-region from about 90 to 115 miles (140 to 180 km) altitude and the F2-region in which the concentration of electrons peaks in the altitude range of 150 to 300 miles (around 250 to 500 km). Most recent map of the Height of Maximum (hmF2). The ionosphere above the peak electron concentration is usually referred to as the Topside Ionosphere.

    Plasmasphere

    The plasmasphere is not really spherical but a doughnut-shaped region (a torus) with the hole aligned with Earth’s magnetic axis. [In this case the use of the suffix -sphere is more in the figurative sense of a “sphere of influence”.] The Earth’s plasmasphere is made of just that, a plasma, the fourth state of matter. (Test your skills on sorting the states of matter with the Matter Sorter.) This plasma is composed mostly of hydrogen ions (protons) and electrons. It has a very sharp edge called the plasmapause. The outer edge of this doughnut over the equator is usually some 4 to 6 Earth radii from the center of the Earth or 12,000-20,000 miles (19,000-32,000 km) above the surface. The plasmasphere is essentially an extension of the ionosphere. Inside of the plasmapause, geomagnetic field lines rotate with the Earth. The inner edge of the plasmasphere is taken as the altitude at which protons replace oxygen as the dominant species in the ionospheric plasma which usually occurs at about 600 miles (1000 km) altitude. The plasmasphere can also be considered to be a structure within the magnetosphere.

    Magnetosphere

    Outside the plasmapause, magnetic field lines are unable to corotate because they are influenced strongly by electric fields of solar wind origin. The magnetosphere is a cavity (also not spherical) in which the Earth’s magnetic field is constrained by the solar wind and interplanetary magnetic field (IMF). The outer boundary of the magnetosphere is called the magnetopause. The magnetosphere is shaped like an elongated teardrop (like a Christmas Tree ornament) with the tail pointing away from the Sun. The magnetopause is typically located at about 10 Earth radii or some 35,000 miles (about 56,000 km) above the Earth’s surface on the day side and stretches into a long tail, the magnetotail, a few million miles long (about 1000 Earth radii), well past the orbit of the Moon (at around 60 Earth radii), on the night side of the Earth. However, the Moon itself is usually not within the magnetosphere except for a couple of days around the Full Moon.

    Beyond the magnetopause are the magnetosheath and bow shock which are regions in the solar wind disturbed by the presence of Earth and its magnetic field.

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  22. vertical classification of atmosphere
    Vertical structure of the atmosphere

    1.4.1. Vertical change of composition

    According to the homogeneity of atmospheric composition, two layers can be defined in the atmosphere. The lower layer, up to an altitude of about 80 km above sea level is the homosphere, where due to the continuous turbulent mixing the composition of the atmosphere is relatively constant for chemical species which have long mean residence times. This region is closed by a thin transition layer, called turbopause. Above the turbopause, in the heterosphere, the molecular diffusion dominates and the chemical composition of the atmosphere becomes stratified and varies according to the molecular mass of chemical species (Figure 1.7). The lower heterosphere are dominated by nitrogen and oxygen molecules and the lighter gases being concentrated in the higher layers. Up to 1,000 km the oxygen atoms and above this height the helium and hydrogen are the dominant species.

    In the upper part of the atmosphere – from about 60 km to 2000 km above the Earth’s surface – ionic species or free radicals (O+, O2+, NO+, N2+, free electrons) can also be found, and high number of ionized particles affect the propagation of radio waves. This region of the atmosphere is called ionosphere. There are three important layers in the lower part of the ionosphere (at altitudes between about 60 km and 600 km), where the absorption of solar extreme ultraviolet radiation and x-rays ionize the neutral atmosphere. These are the D (60–90 km), E (90–150 km) and F regions (150–500 km) with F1 and F2 sub-layers. The ion density of each layer depends on the solar activity and time of day (Figure 1.8).

    Vertical structure of the atmosphere: the homosphere and the heterosphere
    Figure 1.7: Vertical structure of the atmosphere according to chemical composition

    The layers of the ionosphere
    Figure 1.8: The layers of the ionosphere

    1.4.2. Vertical temperature changes

    Based on the variation of temperature with height, the atmosphere can be divided to different layers (Figure 1.9).

    Troposphere:

    The lowest major atmospheric layer is the troposphere, extending from the Earth’s surface to the tropopause (Figure 1.9). The thickness of the troposphere varies with latitude: it is about 7 km in polar region, generally 11–12 km in the mid-latitudes and even 18 km over the Equator. The height of the tropopause is also depends on season, weather condition and time of day.

    Figure 1.9: The vertical structure of the atmosphere according to the vertical temperature changes

    Troposphere contains about 80% of total mass of the atmosphere, nearly all water vapour and dust particles can be found here. Almost all weather phenomena and cloud formation take place in this layer. The troposphere is heated from below by the Earth’s surface. Incoming solar radiation first warms the surface, which radiates heat into the atmosphere. The warmer air in the near surface layer generates turbulent vertical motions, which transfer water vapour and other tracers to higher altitudes.

    Temperature decreases with increasing height in the troposphere to away from the warming surface. The changing rate of temperature with height is called “lapse rate”[11]. Tropospheric air temperature is generally proportional with distance from surface and lapse rate is fairly uniform, it is about 6,5 °C / 1000 m, but this rate is affected by water vapour content. Temperature is generally lower than –50 °C at the top of the troposphere (in mid-latitude, temperature is –56.5 °C at 11 km based on ICAO standard atmosphere[12]).

    However, in the lower troposphere, the atmospheric stratification can differ from normal, and temperature can increase with height in the function of time of day and weather condition. This situation is called inversion[13], which generally occurs at night. When temperature remains the same with height, the stratification is isothermal. The atmospheric stratification and thereby the stability conditions play important role in dispersion of tracers.

    The troposphere can be divided into two main parts. The lower part is the planetary boundary layer (PBL) or atmospheric boundary layer, extending upward from the surface to a height that ranges from about 100 to 3000 m in the function of season, weather condition and time of day. Above this layer, the free troposphere can be found.

    Stratosphere:

    At the tropopause, the decrease of temperature halts and to about 50 km above ground level, an inversion layer can be found, when temperature increases with height. This layer is the stratosphere. Temperature increase in the stratosphere (Figure 1.9) is due to the relatively high concentration of ozone. Ozone strongly absorbs uv radiation[14] from the Sun in the bands between 210 and 290 nm (more information about ozone see Chapter 8). This absorption by the ozone is the primary cause of temperature increase in the stratosphere. Without ozone layer, a further decrease of temperature with increasing height would be observable in the stratosphere (Figure 1.10).

    Stratosphere holds about 19% of total mass of the atmosphere, and it contains only a very small amount of water vapour. Due to the vertical stratification, stratosphere is a stable layer and the mixing is weak. Particles that reach the stratosphere from the troposphere (e.g. from a large volcanic eruption) can stay a long time (many years) in the stratosphere without removing from it. Polar stratospheric clouds[15] (PSCs) can be observed in winter polar stratosphere between 15 and 25 km height. They form at only very low temperature (below −78 °C). Different types of PSCs contain water, and different particles (e.g. nitric acids) or only water ice (see more information about polar stratospheric clouds in Chapter 8).

    The stratosphere is bounded above by the stratopause at about 50 km height, where the average temperature is generally just below 0 °C.

    The role of stratospheric ozone in temperature profile
    Figure 1.10: Real and hypothetical vertical profile of temperature with and without ozone in the stratosphere, respectively.

    Mesosphere:

    Over the stratopause, the next layer is the mesosphere from about 50 km to 85–100 km above the Earth’s surface (Figure 1.9). Air density is tow low to absorb solar radiation, thus the mesosphere is warmed from below by the stratosphere and hence the temperature decreases with increasing height. However the atmosphere is still thick enough to slow down meteoroids enter to the atmosphere. The upper boundary of mesosphere is the mesopause, which is the coldest region of Earth’s atmosphere, where the temperature is around –100 °C.

    Within the mesosphere, noctilucent clouds[16] can be appeared, when Sun is below the horizon and the lower layers of the atmosphere are in the Earth’s shadow. These thin clouds are composed from tiny ice crystals, but their emergences, properties and relationships with global climate change are still not fully understood.

    Upper atmospheric electrical discharges (like red sprites or blue jets) over tropospheric thunderstorms also occur in the mesosphere.

    However, in the absence of frequent direct measurements (only by occasionally sounding rockets), mesosphere is a less known layer of the atmosphere.

    Thermosphere:

    In the thermosphere, over the mesopause, temperature rise continually with increasing height due to the direct absorption of high energy solar radiation by atmospheric gases. Temperatures are highly dependent on solar activity, and can rise well beyond to 1000 °C. However, this value is not comparable to those of the lower part of the atmosphere, as the air density is extremely low in this layer.

    Considering the composition, this layer is a part of the heterosphere, where the atmospheric compounds stratified by their molecular mass. Major layers of the ionosphere (see above) are situated in the thermosphere. Auroras, form by collisions of energetic charged particles with atoms, occur also in the thermosphere.

    Over about 500–1000 km above the Earth’s surface (depending on solar activity), the collisions between atmospheric constituent become negligible. This layer is often called as exosphere, which gradually merge into interplanetary space.

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  23. Atmospheric Aerosols: What Are They, and Why Are They So Important?
    Aerosols are minute particles suspended in the atmosphere. When these particles are sufficiently large, we notice their presence as they scatter and absorb sunlight. Their scattering of sunlight can reduce visibility (haze) and redden sunrises and sunsets.

    Dispersion of volcanic aerosols
    The dispersal of volcanic aerosols has a drastic effect on Earth’s atmosphere. Follow an eruption, large amounts of sulphur dioxide (SO2), hydrochloric acid (HCL) and ash are spewed into Earth’s stratosphere. HCL, in most cases, condenses with water vapor and is rained out of the volcanic cloud formation. SO2 from the cloud is transformed into sulphuric acid, H2SO4. The sulphuric acid quickly condenses, producing aersol particles which linger in the atmosphere for long periods of time. The interaction of chemicals on the surface of aerosols, known as heterogeneous chemistry, and the tendency of aerosols to increase levels of chlorine gas react with nitrogen in the stratopshere, is a prime contributor to stratospheric ozone destruction.
    Credits: NASA
    Aerosols interact both directly and indirectly with the Earth’s radiation budget and climate. As a direct effect, the aerosols scatter sunlight directly back into space. As an indirect effect, aerosols in the lower atmosphere can modify the size of cloud particles, changing how the clouds reflect and absorb sunlight, thereby affecting the Earth’s energy budget.

    Aerosols also can act as sites for chemical reactions to take place (heterogeneous chemistry). The most significant of these reactions are those that lead to the destruction of stratospheric ozone. During winter in the polar regions, aerosols grow to form polar stratospheric clouds. The large surface areas of these cloud particles provide sites for chemical reactions to take place. These reactions lead to the formation of large amounts of reactive chlorine and, ultimately, to the destruction of ozone in the stratosphere. Evidence now exists that shows similar changes in stratospheric ozone concentrations occur after major volcanic eruptions, like Mt. Pinatubo in 1991, where tons of volcanic aerosols are blown into the atmosphere (Fig. 1).

    Volcanic Aerosol

    Three types of aerosols significantly affect the Earth’s climate. The first is the volcanic aerosol layer which forms in the stratosphere after major volcanic eruptions like Mt. Pinatubo. The dominant aerosol layer is actually formed by sulfur dioxide gas which is converted to droplets of sulfuric acid in the stratosphere over the course of a week to several months after the eruption (Fig. 1). Winds in the stratosphere spread the aerosols until they practically cover the globe. Once formed, these aerosols stay in the stratosphere for about two years. They reflect sunlight, reducing the amount of energy reaching the lower atmosphere and the Earth’s surface, cooling them. The relative coolness of 1993 is thought to have been a response to the stratospheric aerosol layer that was produced by the Mt. Pinatubo eruption. In 1995, though several years had passed since the Mt. Pinatubo eruption, remnants of the layer remained in the atmosphere. Data from satellites such as the NASA Langley Stratospheric Aerosol and Gas Experiment II (SAGE II) have enabled scientists to better understand the effects of volcanic aerosols on our atmosphere.

    Desert Dust

    The second type of aerosol that may have a significant effect on climate is desert dust. Pictures from weather satellites often reveal dust veils streaming out over the Atlantic Ocean from the deserts of North Africa. Fallout from these layers has been observed at various locations on the American continent. Similar veils of dust stream off deserts on the Asian continent. The September 1994 Lidar In-space Technology Experiment (LITE), aboard the space shuttle Discovery (STS-64), measured large quantities of desert dust in the lower atmosphere over Africa (Fig. 2). The particles in these dust plumes are minute grains of dirt blown from the desert surface. They are relatively large for atmospheric aerosols and would normally fall out of the atmosphere after a short flight if they were not blown to relatively high altitudes (15,000 ft. and higher) by intense dust storms.

    LITE Measurements Over Northwestern Africa, Atlas Mountains
    Fig. 1 – LITE Measurements Over Northwestern Africa, Atlas Mountains
    Credits: NASA
    Because the dust is composed of minerals, the particles absorb sunlight as well as scatter it. Through absorption of sunlight, the dust particles warm the layer of the atmosphere where they reside. This warmer air is believed to inhibit the formation of storm clouds. Through the suppression of storm clouds and their consequent rain, the dust veil is believed to further desert expansion.

    Recent observations of some clouds indicate that they may be absorbing more sunlight than was thought possible. Because of their ability to absorb sunlight, and their transport over large distances, desert aerosols may be the culprit for this additional absorption of sunlight by some clouds.

    Human-Made Aerosol

    The third type of aerosol comes from human activities. While a large fraction of human-made aerosols come in the form of smoke from burning tropical forests, the major component comes in the form of sulfate aerosols created by the burning of coal and oil. The concentration of human-made sulfate aerosols in the atmosphere has grown rapidly since the start of the industrial revolution. At current production levels, human-made sulfate aerosols are thought to outweigh the naturally produced sulfate aerosols. The concentration of aerosols is highest in the northern hemisphere where industrial activity is centered. The sulfate aerosols absorb no sunlight but they reflect it, thereby reducing the amount of sunlight reaching the Earth’s surface. Sulfate aerosols are believed to survive in the atmosphere for about 3-5 days.

    The sulfate aerosols also enter clouds where they cause the number of cloud droplets to increase but make the droplet sizes smaller. The net effect is to make the clouds reflect more sunlight than they would without the presence of the sulfate aerosols. Pollution from the stacks of ships at sea has been seen to modify the low-lying clouds above them. These changes in the cloud droplets, due to the sulfate aerosols from the ships, have been seen in pictures from weather satellites as a track through a layer of clouds. In addition to making the clouds more reflective, it is also believed that the additional aerosols cause polluted clouds to last longer and reflect more sunlight than non-polluted clouds.

    Climatic Effects of Aerosols

    Astronaut Carl J. Meade tests SAFER system with LITE in background
    Sept. 16, 1994 – Astronaut Carl J. Meade tests the new Simplified Aid for EVA Rescue (SAFER) system 130 nautical miles above Earth. The hardware supporting the LIDAR-in-Space Technology Experiment (LITE) is in the lower right. A TV camera on the Remote Manipulator System arm records the Extravehicular Activity.
    Credits: NASA
    The additional reflection caused by pollution aerosols is expected to have an effect on the climate comparable in magnitude to that of increasing concentrations of atmospheric gases. The effect of the aerosols, however, will be opposite to the effect of the increasing atmospheric trace gases – cooling instead of warming the atmosphere.

    The warming effect of the greenhouse gases is expected to take place everywhere, but the cooling effect of the pollution aerosols will be somewhat regionally dependent, near and downwind of industrial areas. No one knows what the outcome will be of atmospheric warming in some regions and cooling in others. Climate models are still too primitive to provide reliable insight into the possible outcome. Current observations of the buildup are available only for a few locations around the globe and these observations are fragmentary.

    Understanding how much sulfur-based pollution is present in the atmosphere is important for understanding the effectiveness of current sulfur dioxide pollution control strategies.

    The Removal of Aerosols

    It is believed that much of the removal of atmospheric aerosols occurs in the vicinity of large weather systems and high altitude jet streams, where the stratosphere and the lower atmosphere become intertwined and exchange air with each other. In such regions, many pollutant gases in the troposphere can be injected in the stratosphere, affecting the chemistry of the stratosphere. Likewise, in such regions, the ozone in the stratosphere is brought down to the lower atmosphere where it reacts with the pollutant rich air, possibly forming new types of pollution aerosols.

    Aerosols As Atmospheric Tracers

    Aerosol measurements can also be used as tracers to study how the Earth’s atmosphere moves. Because aerosols change their characteristics very slowly, they make much better tracers for atmospheric motions than a chemical species that may vary its concentration through chemical reactions. Aerosols have been used to study the dynamics of the polar regions, stratospheric transport from low to high latitudes, and the exchange of air between the troposphere and stratosphere.

    Future NASA Aerosol Studies

    NASA’s ongoing Atmospheric Effects of Aviation Project (AEAP) has measured emissions from the engines of several commercial and research aircraft. Jet engine emissions have been shown to affect the concentrations of atmospheric water vapor and aerosols, and they may affect how clouds form and the concentrations of atmospheric ozone. Few actual measurements of their effects have been made, however.

    In the spring of 1996, the Subsonic Aircraft Contrail and Cloud Effects Special Study (SUCCESS) focused on subsonic aircraft contrails and the impact of the aerosols in those contrails on cirrus clouds and atmospheric chemistry. Researchers have determined that aircraft contrails can prolong the presence of high altitude cirrus clouds while also decreasing the size of the ice crystals that make up the clouds.Studies like SUCCESS and AEAP will be ongoing as scientists continue to try to understand how aerosols affect our atmosphere and climate.

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  24. composition of atmosphere-
    9.1 COMPOSITION OF ATMOSPHERE
    The atmosphere is made up of different types of gases, water rapour and dust
    particles. The composition of the atmosphere is not static. It changes according to
    the time and place.
    (A) Gases of the atmosphere:
    The atmosphere is the mixture of different types of gases, including water
    vapour and dust particles. Nitrogen and Oxygen are the two main gases of
    the atmosphere. 99 percent part of it is made up of these two gases. Other
    gases like organ, carbon dioxide, hydrogen, nion, helium etc. form the
    remaining part of atmosphere. The details of different gases of the atmosphere
    are given in the table No. 9.1 and Fig. No. 9.1
    Table 9.1 : Amount of gases in the dry and
    air of the atmosphere.
    Serial No. Gas Amount (in percentage)
    A. Main
    1. Nitrogen 78.1
    2. Oxygen 20.9
    B. Secondary
    1. Organ 0.9
    2. Carbon Dioxide 0.03
    3. Hydrogen 0.01
    4. Nion 0.0018
    5. Helium 0.0005
    6. Ozone 0.00006
    7. Others
    99%
    0.99%
    Fig. 9.1 Composition of Atmosphere
    MODULE – 4
    166
    Atmosphere Composition and Structure
    Notes
    The domain of Air on
    the Earth
    GEOGRAPHY
    Ozone Gas
    The amount of ozone gas in the atmosphere is very little. It is limited to the ozone
    layer but it is very important. It protects the living beings by absorbing the ultraviolet
    rays of the sun. If there was no ozone gas in the atmosphere, there would
    not have been existence of living beings and plants on the earth surface.
    (B) Water vapour
    Gaseous form of water persent in the atmosphere is called water vapour. Water
    vapour present in the atmosphere has made life possible on the earth Water vapour
    is the source of all kinds of precipitation. Its maximum amount in the atmosphere
    could be upto 4 percent. Maximum amount of water vapour is found in hot-wet
    regions and its least amount is found in the dry regions. Generally, the amount of
    water vapour goes on decreasing from low latitudes to high latitudes.
    In the same way, its amount goes on decreasing with increasing altitude. Water
    vapour reaches in the atmosphere through evaporation and transpiration.
    Evaporation takes place in the oceans, seas, rivers, ponds and lakes while
    transpiration takes lace from the plants, trees and living beings.
    (c) Dust Particles
    Dust particles are generally found in the lower layers of the atmosphere. These
    particles are found in the form of sand, smoke and oceanic salt. Sand particle have
    important place in the atmosphere. These dust particles help in the condensation
    of water vapour. During condensation water vapour gets condensed in the form of
    droplets around these dust particles. Due to this process the clouds are formed
    and precipitation is made possible.

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  25. Profile photo of binoop binoop says:

    Meteorology: definition- branches of meteorology
    Meteorology is the study of Earth’s atmosphere. Study about the difference between meteorology and climatology, and explore the history and interdisciplinary nature of its study.
    Meteorology and Climatology:-climate’ and ‘weather’ refer to the same things, and therefore are both part of meteorology. In reality, climate and weather are two very different concepts that can easily be distinguished from one another .

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  26. Atmospheric profile
    Why measure the weather?

    The science of the study of weather is called meteorology; the meteorologist measures temperature, rainfall, pressure, humidity, sunshine and cloudiness, and makes predictions and forecasts about what the weather will do in the future.

    Atmospheric profile :The Atmosphere is divided into layers according to major changes in temperature. Gravity pushes the layers of air down on the earth’s surface. This push is called Air Pressure 99% of the total mass of the atmosphere is below 32 kilometers.
    Troposphere – 0 to 12 km – Contains 75% of the gases in the atmosphere. This is where you live and where weather occurs. As height increases, temperature decreases. The temperature drops about 6.5 degrees Celsius for every kilometer above the earth’s surface.
    Tropopause – located at the top of the troposphere. The temperature remains fairly constant here. This layer separates the troposphere from the stratosphere. We find the jet stream here. These are very strong winds that blow eastward.
    Stratosphere – 12 to 50 km – in the lower part of the stratosphere. The temperature remains fairly constant (-60 degrees Celsius). This layer contains the ozone layer. Ozone acts as a shield for in the earth’s surface. It absorbs ultraviolet radiation from the sun. This causes a temperature increase in the upper part of the layer.

    Mesosphere – 50 to 80 km – in the lower part of the stratosphere. The temperature drops in this layer to about -100 degrees Celsius. This is the coldest region of the atmosphere. This layer protects the earth from meteoroids. They burn up in this area.

    Thermosphere – 80 km and up – The air is very thin. Thermosphere means “heat sphere”. The temperature is very high in this layer because ultraviolet radiation is turned into heat. Temperatures often reach 2000 degrees Celsius or more. This layer contains:
    2. Ionosphere – This is the lower part of the thermosphere. It extends from about 80 to 550 km. Gas particles absorb ultraviolet and X-ray radiation from the sun. The particles of gas become electrically charged (ions). Radio waves are bounced off the ions and reflect waves back to earth. This generally helps radio communication. However, solar flares can increase the number of ions and can interfere with the transmission of some radio waves.
    3. Exosphere – the upper part of the thermosphere. It extends from about 550 km for thousands of kilometers. Air is very thin here. This is the area where satellites orbit the earth.
    Magnetosphere – the area around the earth that extends beyond the atmosphere. The earth’s magnetic field operates here. It begins at about 1000 km. It is made up of positively charged protons and negatively charged electrons. This traps the particles that are given off by the sun. They are concentrated into belts or layers called the Van Allen radiation belts. The Van Allen belts trap deadly radiation. When large amounts are given off during a solar flare, the particles collide with each other causing the aurora borealis or the northern lights.

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  27. unit 1
    Meteorology is the interdisciplinary scientific study of the atmosphere.
    Branches.
    Climatology
    Synoptic Meteorology
    Dynamic Meteorology
    Physical Meteorology
    Agricultural Meteorology
    Applied Meteorology

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  28. unit-2
    Elements of weather and climate
    a) Temperature is how hot or cold the atmosphere is, how many degrees Celsius
    (centigrade) it is above or below freezing (0°C). Temperature is a very
    important factor in determining the weather, because it influences or controls
    other elements of the weather, such as precipitation, humidity, clouds and
    atmospheric pressure.
    b) Humidity is the amount of water vapour in the atmosphere.
    c) Precipitation is the term given to moisture that falls from the air to the ground.
    Precipitation includes snow, hail, sleet, drizzle, fog, mist and rain.
    d) Atmospheric pressure (or air pressure) is the weight of air resting on the
    earth’s surface. Pressure is shown on a weather map, often called a synoptic
    map, with lines called isobars.
    e) Wind is the movement of air masses from high pressure areas (highs) to low
    pressure areas (lows).

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  29. Meteorology: definition- branches of meteorology
    Meteorology is the study of Earth’s atmosphere. Learn about the difference between meteorology and climatology, and explore the history and interdisciplinary nature of its study.
    Meteorology and Climatology:-climate’ and ‘weather’ refer to the same things, and therefore are both part of meteorology. In reality, climate and weather are two very different concepts that can easily be distinguished from one another . Meteorology is concerned with the current state of the atmosphere at a given time and place, whereas climatology-long-term average weather conditions and trends for a given location. Climatology can be looked at as the historical record of weather conditions for a location, while meteorology would be the current events or daily news stories for that same location.

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  30. Meteorology: definition- branches of meteorology
    Meteorology is the study of Earth’s atmosphere. Learn about the difference between meteorology and climatology, and explore the history and interdisciplinary nature of its study.

    Report user
  31. Weather elements- definition and units of measurement
    Why measure the weather?

    The science of the study of weather is called meteorology; the meteorologist measures temperature, rainfall, pressure, humidity, sunshine and cloudiness, and makes predictions and forecasts about what the weather will do in the future.

    Report user
  32. Is it just me?
    Did any body else find any contents within each units? I’m confused.

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