OUR ATMOSPHERE

By

 

Bhaskar Karnick & V Krishna Moorthy

 

 

Contents

Introduction

Creator The Sun

Atmosphere History

The layers of Atmosphere
Van Allen radiation belts

The Energy Balance

The mechanism of winds

The Clouds

The Green House Effect

The Communication and Atmosphere

Radiation Hazards

Conclusion
Reference Links


Introduction

 

The life on the planet Earth is possible because of the environment on the Planet is conductive to support life. Life  is supported by the atmosphere, solar energy, and our planet's magnetic fields. The atmosphere absorbs the energy from the Sun, recycles water and other chemicals, and works with the electrical and magnetic forces to provide a moderate climate. The atmosphere also protects us from high-energy radiation and the frigid vacuum of space.

 

Are we alone in the universe?  - That question appears to be unanswerable in the near future.


Let us have a closer view of our environment......................

 

Our environment is largely consists lithosphere (land) surrounded by hydrosphere (water) and the immediate atmosphere (air) along with all its characteristics. The atmosphere is a mixture of gases surrounding the earth and held by the earth's gravity. One can not deny the influence of all other celestial bodies on the earths environment how ever insignificant it may be.

  
It is thought that initially earth had no atmosphere. Volcanoes grew and erupted on barren earth, gases began to form an atmosphere. This early atmosphere did not contain oxygen. Plants appeared and developed a way to use the sun's energy to produce oxygen in the air. This process is called photosynthesis. The first oxygen-breathing animals appeared about 500 million years ago.

Earth's atmosphere consist of layers of gases surrounding the planet Earth and retained by the Earth's gravity. Without gravity, the gasses would have escaped to outer space. The composition of atmospheric  gases being nitrogen (78.1%) and oxygen (20.9%), with small amounts of argon (0.9%), carbon dioxide in varying quantity (around 0.035%), water vapor, and other gases. The atmosphere protects life on Earth by absorbing ultraviolet, cosmic/solar radiation and reducing temperature extremes between day and night.

Density of atmosphere does not change suddenly, but rather thins gradually with increasing altitude, there is no definite boundary between the atmosphere and outer space. 75% of the atmosphere is within 11 km of the planetary surface. The altitude of 100 kilometres  is considered  the boundary between atmosphere and space.

 

Creator The Sun

The Sun is an average Star, The Sun  produces  about 3.8 x 1023 kilo Watts (or kilo Joules/sec) of energy. Nuclear fusion takes place in  the Sun due high temperature and density in the core of the Sun resulting in release of unimaginable amount of energy and creating helium as a byproduct. The core is so dense that energy released at the center of the Sun is estimated to take about 50,000,000 years to make to the surface.

Sun is neither featureless nor steady. (Theophrastus first identified sunspots in the year 325 B.C.) Some of the more noticeable solar features are:

 Sunspots:

Sunspots are the dark areas on the solar surface, They are transient, concentrated magnetic fields. Sunspot are the most prominent visible features on the Sun; a moderate-sized sunspot is about as large as Earth. Sunspots form and dissipate over periods of days or weeks. They occur when strong magnetic fields emerge through the solar surface and allow the area to cool slightly.

 Coronal Holes

Coronal holes are variable solar features that can last for months to years. They are seen as large, dark holes when the Sun is viewed in x-ray wavelengths. These holes are rooted in large cells of unipolar magnetic fields on the Sun's surface.

Prominences

Solar prominences (seen as dark filaments on the disk) are usually quiescent clouds of solar material held above the solar surface by magnetic fields. Most prominences erupt at some point in their lifetime, releasing large amounts of solar material into space.

Flares

Solar flares are intense, temporary releases of energy. They are seen at ground-based observatories as bright areas on the Sun in optical wavelengths and as bursts of noise at radio wavelengths; they can last from minutes to hours.   

Coronal Mass Ejections

The outer solar atmosphere, the corona, is structured by strong magnetic fields. Where these fields are closed, often above sunspot groups, the confined solar atmosphere can suddenly and violently release bubbles or tongues of gas and magnetic fields called coronal mass ejections.  

Between Sun and Earth

The region between the Sun and the planets has been termed the interplanetary medium. Although once considered a perfect vacuum, this is actually a turbulent region dominated by the solar wind, which flows at velocities of approximately 250-1000 km/s (about 600,000 to 2,000,000 miles per hour).  

 Solar Effects at Earth

Some major terrestrial results of solar variations are the aurora, proton events, and geomagnetic storms.

 

Aurora

The aurora is a dynamic and visually delicate manifestation of solar-induced geomagnetic storms. The solar wind energizes electrons and ions in the magnetosphere. These particles usually enter Earth's upper atmosphere near the polar regions. When the particles strike the molecules and atoms of the thin, high atmosphere, some of them start to glow in different colors.

Proton Events

Energetic protons can reach Earth within 30 minutes of a major flare's peak. During such an event, Earth is showered energetic solar particles (primarily protons) released from the flare site.

Geomagnetic Storms

Flare or eruptive prominence occurs frequently, a slower cloud of solar material and magnetic fields reaches Earth, buffeting the magnetosphere and resulting in a geomagnetic storm.  

Atmosphere History

 

The history of the Earth's atmosphere is  poorly understood. The present atmosphere is sometimes referred to as its "third atmosphere", in order to distinguish the current chemical composition from earlier two notably different compositions. The original atmosphere was primarily helium and hydrogen; heat (from the still molten crust, and the sun) dissipated this atmopshere.

About 3.5 billion years ago, the surface had cooled enough to form a crust, still heavily populated with volcanoes which released steam, carbon dioxide, and ammonia. This led to the "second atmosphere"; which was, primarily, carbon dioxide and water vapor, with some nitrogen but virtually no oxygen. This second atmosphere had ~100 times as much gas as the current atmosphere. It is generally believed that the greenhouse effect, caused by high levels of carbon dioxide, kept the Earth from freezing.

During the next few billion years, water vapor condensed to form rain and oceans, which began to dissolve carbon dioxide. Approximately 50% of the carbon dioxide would be absorbed into the oceans. Photosynthesizing plants would evolve and convert carbon dioxide into oxygen. Over time, excess carbon became locked in fossil fuels, sedimentary rocks (notably limestone), and animal shells. As oxygen was released, it reacted with ammonia to create nitrogen; in addition, bacteria would also convert ammonia into nitrogen.

As more plants appeared, the levels of oxygen increased significantly (while carbon dioxide levels dropped). At first it combined with various elements (such as iron), but eventually oxygen accumulated in the atmosphere resulting in mass extinctions and further evolution. With the appearance of an ozone layer (a compound of oxygen atoms) lifeforms were better protected from ultraviolet radiation. This oxygen-nitrogen atmosphere is the "third atmosphere".

The Layers Atmosphere
 

 The Earths atmosphere is gaisous. The atmosphere is divided in to layers though the properties do not change suddenly but appreciable changes occure at these loosly defined boundries.

Temperature and the atmospheric layers

The temperature of the Earth's atmosphere varies with altitude; the mathematical relationship between temperature and altitude varies between the different atmospheric layers:

The boundaries between these regions are named the tropopause, stratopause and mesopause.

The average temperature of the atmosphere at the surface of earth is 14 C.

Troposphere

The troposphere starts at the Earth's surface and extends 8 to 14.5 kilometers high (5 to 9 miles). This part of the atmosphere is the most dense. As you climb higher in this layer, the temperature drops from about 17 to -52 degrees Celsius. Almost all weather is in this region. The tropopause separates the troposphere from the next layer. The tropopause and the troposphere are known as the lower atmosphere.

Stratosphere

The stratosphere starts just above the troposphere and extends to 50 kilometers high. Compared to the troposphere, this part of the atmosphere is dry and less dense. The temperature in this region increases gradually to -3 degrees Celsius, due to the absorption of  Ultraviolet Radiation. The ozone layer, which absorbs and scatters the solar ultraviolet radiation, is in this layer. Ninety-nine percent of "air" is located in the troposphere and stratosphere. The stratopause separates the stratosphere from the next layer.

Mesosphere

The mesosphere starts just above the stratosphere and extends to 85 kilometers high. In this region, the temperatures again fall as low as -93 degrees Celsius as you increase in altitude. The chemicals are in an excited state, as they absorb energy from the Sun. The mesopause separates the mesophere from the thermosphere.

The regions of the stratosphere and the mesosphere, along with the stratopause and mesopause, are called the middle atmosphere by scientists. This area has been closely studied on the ATLAS Spacelab mission series.

Thermosphere

The thermosphere starts just above the mesosphere and extends to 600 kilometers high. The temperatures go up as you increase in altitude due to the Sun's energy. Temperatures in this region can go as high as 1,727 degrees Celsius. Chemical reactions occur much faster here than on the surface of the Earth. This layer is known as the upper atmosphere.

Beyond the Atmosphere

The exosphere starts at the top to the thermosphere and continues until it merges with interplanetary gases, or space. In this region of the atmosphere, Hydrogen and Helium are the prime components and are only present at extremely low densities.

Pressure

Atmospheric pressure is the  direct result of the weight of the air. This means that air pressure varies with location and time because the amount (and weight) of air above the earth varies with location and time. Atmospheric pressure drops by ~50% at an altitude of about 5 km (equivalently, about 50% of the total atmospheric mass is within the lowest 5 km). The average atmospheric pressure, at sea level, is about 101.3 kilopascals (about 14.7 pounds per square inch).

 

Imperceptible to the human eye, air is in constant, frantic motion at the surface of the Earth. As in any gas, the molecules (in Earth's case nitrogen and oxygen) are moving and bumping into each other at various speeds. Near the Earth's surface they move at an average of 1,090 miles per hour. Warm the air and the molecules move faster, cool the air and the molecules move more slowly. The impacts of billions and billions of moving molecules cause pressure. At the surface of the Earth the air pressure is greater than at the top layer of the atmosphere 50+ miles above the Earth's surface.

 

But if the whole atmosphere is about 50 miles thick, how can it be that half the pressure is caused by the air in the first 5 Kilo metres? What happens is that the pressure of the air above it, compresses it. The air closer to the Earth's surface has more density, since the molecules are closer together. Near the top of the atmosphere, there is very low air density because there is very little pressure compressing the molecules together. But at the surface of the Earth, the density is much higher. So, the layers of air in the lower atmosphere are more compressed than those above it, and adding much more to the pressure below. As one moves up in altitude, the pressure and density are reduced very quickly.

Density and mass

The density of air at sea level is about 1.2 kilograms per cubic meter. This density decreases at higher altitudes at the same rate that pressure decreases. The total mass of the atmosphere is about 5.1 1018 kg, a tiny fraction of the earth's total mass.

Various atmospheric regions

Atmospheric regions are also named in other ways:

Van Allen radiation belts

The Van Allen belts are a band of concentrated radiation around the Earth.  It's been estimated that you'd need a foot of lead casing to protect yourself from this, which the Apollo crafts didn't have.  Why didn't this kill the astronauts on the way to the moon?

Radiation is a big problem when it comes to space travel and the Earth's magnetic field concentrates this radiation into the Van Allen belts that surround the Earth.   No matter what, the Apollo crafts had to go through these belts and there was no way the Apollo crafts could afford to take all the weight of lead shielding with them.   So they were bound to be exposed.   The question is, just how serious would this exposure be?

What you have to realize that the radiation involved isn't the same kind or intensity as you might get from a nuclear bomb.  You don't fall sick and your hair doesn't all fall out.    It's been calculated that travelling at speed through the Van Allen belt would result in exposure of 1 rem.  Radiation sickness symptoms don't start to show until you get around 25.  Once you reach 100 you're going to be ill.   500 and you're probably dead.   So the exposure the astronauts received is pretty mild.

Energy Balance

 

Over thousands of years the temperature on the Earth has been more or less constant with seasonal variations. This is possible only if the energy received from outer space is same as dissipated from Earth. Otherwise earth will either become too cold or too Hot for life to survive.

The amount of energy received at the edge varies according to location and season. When the sun's rays are perpendicular to a location at the edge of the atmosphere, that area receives the maximum amount of radiation.  Because of the earth's curvature the equator receives a greater amount of solar energy than the poles. The position of the earth relative to the sun also affects the amount of radiation received. When the northern hemisphere experiences summer the North Pole is tilted toward the sun, resulting in a longer period of daylight and more perpendicular rays. Though the earth in its elliptical revolution is actually at its farthest distance from the sun, the amount of energy and the length of daylight compensates for the distance. When the earth is closest to the sun, the North Pole is tilted away and the northern hemisphere experiences winter, short days and oblique rays.

The transfer of energy from the sun to the earth's atmosphere is through radiation. These waves are classified according to their wavelength - the distance between peaks in the waves - from shorter to longer. Differing wavelengths causes differing interactions with the atmosphere; the amount of energy that enters the atmosphere is greatly reduced due to absorption, reflection, and scattering before it reaches the earth's surface.  

Absorption causes energy to be captured and retained by a substance, and by retaining energy the substance heats up and reradiates. X-rays and gamma rays, which have the shortest wavelengths, are absorbed by oxygen and nitrogen molecules in the upper atmosphere and transformed into ions, which form the ionosphere. Ultraviolet rays of slightly longer wavelength are absorbed by ozone in the stratosphere. Infra-red rays, at the other end of the spectrum, are slightly absorbed by carbon dioxide and water vapor in the troposphere. Wavelengths that are visible to the human eye - violet, blue, green, yellow, orange, and red - are affected by reflection and scattering. Reflection occurs when particles and surfaces that are larger than the incoming waves meet and turn back solar energy. Clouds, snow, and light-colored sand are all reflectors. Scattering occurs when particles the same size as the wavelength of the radiation meet. Scattering causes energy to be redirected in all directions, some of which returns to space. The sky appears blue because the short, blue wavelengths are more easily scattered. Without scattering the sky away from the sun would appear black, similar to outer space. Scattering is also the reason the sun appears red at sunrise and sunset. Because the sun's path through the atmosphere is much longer at this time of day, more of the blue wavelengths are scattered out of its beam, leaving more red light.

Only about one-fifth of energy warms the atmosphere directly. Most of the energy that warms our atmosphere comes indirectly from the heated earth. A small amount of the energy absorbed by the earth warms the atmosphere through a process called conduction.  More heat is transferred from the surface to the atmosphere through convection.  

Almost all convection energy is absorbed by the atmosphere. The difference in temperature between the sun and earth changes the wavelength of the convected rays.  Lower the temperature, the longer the wavelength. The shortwave visible light rays which passed down through the water vapor and carbon dioxide without obstruction return upward as long wave radiation and are for the most part absorbed by those same clouds. The clouds heat up and reemit energy back to earth as counter radiation - in effect recycling radiation from the earth. This process of trapping long wave radiation has been called the greenhouse effect, and is one of the important ways the atmosphere's temperatures remain within a livable range.

Amount of energy absorbed by the earth-atmosphere system over the entire globe in a year is equal to the amount emitted by the system.  

 At different latitudes an imbalance exists between the outgoing and absorbed radiation of the earth-atmosphere heating system. The poles should be getting colder and tropical regions warmer, but this is not happening. Heat is being transported pole ward from areas of surplus radiation, almost equally, by ocean and air. The atmospheric balancing act is achieved by wind systems.

The Mechanism of winds

We have seen that heat is transferred vertically from the earth to the air by convection. But wind is defined as the horizontal movement of air relative to the earth's surface.  Air temperature varies because the earth's surface heats up at different rates. Latitude and season, as noted before, cause temperature variations. Large bodies of water warm and cool at a slower rate than large bodies of land. This creates a disparity in the atmosphere above. Because heat decreases with altitude, mountain peaks are cooler than cities at sea level.  

Differences of temperature cause differences in pressure. A difference in pressure across distances is called a pressure gradient, and is the driving force behind wind. 

Once the air has begun to move (surplus heat to the poles and surplus cold to the equator) another force comes into play. This is called the Coriolis force, and is caused by the rotation of the earth.  The earth rotates on its axis at the rate of 1041 miles per hour at the equator. The speed decreases with increasing latitude until it is virtually zero at the poles.  

 

General Wind Patterns

Local wind patterns are the result of pressure differences in the immediate area: land, sea, mountain, etc.  Hot air rises from the equator, creates a low pressure area, and flows towards the north pole. The upper wind flow is deflected to the right by the Coriolis effect, which causes it to pile up and move from west to east. The piled up air cools, creating a high pressure area, and sinks; and as it accumulates on the surface it flows towards both the equator and north pole. The air moving toward the equator is influenced by the Coriolis effect and moves from the northeast, and because of its direction is called the northeast trade winds. Wind is classified according to the direction from which it is blowing. The pole ward moving air also moves to the right and is called the prevailing westerlies. The third wind belt develops as cold polar air sinks and moves south, is deflected to the right, and is therefore called the polar easterlies. The same air pattern occurs in the latitudes of the southern hemisphere, except that the deflection of the wind is to the left rather than right. (In the southern hemisphere the trades are called the southeast trade winds.)

Trade winds occupy the area between 0 (the equator) and 30 degrees latitude; prevailing westerlies the area between 30 and 60 degrees; and polar easterlies the region between 60 and 90 degrees (the pole). The zones that separate these three major wind belts are also identified. Near the equator is a region called the doldrums, literally meaning "stagnation or listlessness". The area was given this name by 16th century English merchant sailors, who found themselves trapped by lack of a "trade" wind to carry them onward to the next port of call. A more explanatory, if less colorful, name is the inter tropical convergence, for it is here that the trade winds of both hemispheres meet. It is known for its extremely low pressure, frequent thunderstorms, and very calm wind. At about 30 degrees is a high pressure area where the trades and westerlies diverge and go toward the equator and pole, respectively. Like the doldrums, it is an area with little wind; unlike the doldrums, there are no cloud formations, just blue skies and warm temperatures. The sailors gave this region a graphic name, the horse latitudes. The origin of the name varies: some say that horses being transported from the old to new world (from Europe to America) grew extremely restless under the dry, still skies, panicked, and had to be pushed overboard; others say it was the sailors who grew terrified of being stranded forever in still seas and jettisoned their cargo in hopes of movement with a lighter load. In any event, ships tried to avoid this zone and its lack of wind. The third zone lies at about 60 degrees latitude, and is called the polar front. Its location varies with the seasons, since the polar front moves south in winter and north in the summer. The cold polar easterlies meet the warm prevailing westerlies in this zone, and because of the extreme differences in pressure, dramatic weather conditions occur.

Jet Streams

The jet stream is a band of fast moving, high altitude air. Friction from the earth's surface slows down air movement, but at higher altitudes friction has no effect and air travels faster. Another factor contributing to jet streams is pressure gradient.  

Cyclones

In the northern hemisphere, air flows around a low pressure area in a counter clock wise direction. At the earth's surface, the air spirals toward the center and converges. This convergence and rotation around a low pressure area is called a cyclone. The circulation forces the air upward, and these rising convection currents carry heat and moisture which results in cooling, clouds, and precipitation. In contrast, high pressure areas in the northern hemisphere circulate wind in an outward, clockwise direction. The air moving down to replace the diverging air results in drier air. This results in  fewer clouds, and clear crisp weather. Because it is the opposite of a cyclone, this movement of air around a high pressure area is called an anticyclone.

 Hurricanes

A mid-latitude cyclone and a tropical cyclone have only two things in common: They each have a low pressure area, and they each create bad weather. A mid- latitude cyclone can occur at any time of the year; a tropical cyclone occurs most often in the summer. A mid-latitude cyclone moves in a westerly direction and takes an elliptical shape; a tropical cyclone moves from east to west and is circular in shape. A mid-latitude cyclone is accompanied by an anticyclone and frontal boundaries; a tropical cyclone has neither.

A tropical cyclone originates off the coast of large continents and over very warm water. The rising and release of water vapor as latent heat provides the energy that intensifies the storm. Interestingly, tropical cyclones do not originate over the doldrums because there is no Coriolis force to help develop sufficient rotary motion. A distinguishing feature of a tropical cyclone is its eye, a calm in the center of the storm that is the result of subsiding warm air; this calmness is in sharp contrast to the eye wall, an upward whirl of thunderstorms that sometimes reach into the stratosphere. A tropical cyclone has different names in different parts of the world, such as typhoon and willy-willy. In the United States, when a tropical storm establishes a closed wind circulation that reaches 72 mph, it is called a hurricane.  

Tornadoes

A tornado is the most devastating of cyclonic winds. Tornadoes usually form near fast-moving cold fronts, and/or from within severe thunderstorms. The clash of air masses with differing layers of temperature, moisture, wind flow and density produces unstable, turbulent air movement. From within a thundercloud a funnel suddenly appears and bobs up and down as it moves toward the earth's surface. Whatever it touches on the ground is instantly destroyed: The intensely spiraling air and extreme pressure gradient cause buildings to literally explode as the air within them seeks to rush outward. Most tornadoes occur in the mid west and southeast United States in the spring and early summer as cold dry air from the pole meets warm moist air from the tropics.

The Clouds

Clouds are formed when air contains as much water vapor (gas) as it can hold. This is called the saturation point, and it can be reached in two ways. First, moisture accumulates until it reaches the maximum amount the volume of air can hold. The other method reduces the temperature of the moisture filled air, which in turn lowers the amount of moisture it can contain. Saturation, therefore, is reached through evaporation and condensation, respectively. When saturation occurs, moisture becomes visible water droplets in the form of fog and clouds.

Condensation by itself does not cause precipitation (rain, snow, sleet, hail). The moisture in clouds must become heavy enough to succumb to gravity and return to earth's surface. This occurs through two processes. In cold clouds ice crystals and water droplets exist side by side. Due to an imbalance of water vapor pressure, the water droplets transfer to the ice crystals. The crystals eventually grow heavy enough to fall to earth. In the second process, water droplets in warm clouds collide and change their electric charge. Droplets of unlike charge attract one another and merge, thereby growing until they have sufficient weight to fall.

There is no difference between fog and clouds other than altitude. Fog is defined as a visible moisture that begins at a height lower than 50 feet. If the visible moisture begins at or above 50 feet, it is called a cloud. Two common types of fog are called radiation fog and advection fog. Radiation fog forms during the night as the earth's surface cools and the air immediately above it cools in turn by conduction. If the air is moist enough, the cooling causes it to reach saturation and visible water droplets form. We often call this type of fog ground fog because it lies so close to the surface. Advection fog forms when warm moist air moves over a colder surface (advection means to move horizontally). A perfect example is on the west coast of continents. Prevailing westerly winds move moist air from over a warm ocean area to over the colder waters off the coast. Fog forms and is carried by the westerly over the land.

Clouds can form anywhere in the troposphere, and although condensed liquid, they are light enough to float in the air and move from place to place by the wind. Clouds are classified according to appearance and height. Based on appearance, there are two major types: Clouds of vertical development, formed by the condensation of rising air; and clouds that are layered, formed by condensation of air without vertical movement. When clouds are classified by height, there are four classes: high, middle, low, and vertical development.

Cloud names, of which there are twelve, combine appearance and height. A brief description of the root name will indicate this combination of features.

Stratus, strato

Layered or sheetlike

Cumulus, cumulo

Puffy, heaped (vertical)

Nimbus, nimbo

Dark and rainy

Cirrus, cirro

Curly, featherlike (high cloud)

Alto

High (but used to describe a middle cloud)

Fracto

Broken

The opposite of fog, in terms of altitude, are cirrus clouds. These clouds develop at an average height of 20,000 feet. Cirrus clouds look like a person's hair, or feathers blowing in the wind. At this altitude, the air is so cold that the cloud is composed of ice crystals rather than water droplets found at lower altitudes. The strong wind at this high altitude blow the clouds in long streamers across the sky.

Another cloud that is formed looks like sheets across the sky. These are stratus clouds. Stratus clouds form when condensation happens at the same level at which the air stops rising. We notice this on days when the stratus clouds are spread across the sky and it becomes overcast. The skies may have these stratus clouds for days and it also brings rain.

Cumulus clouds are the clouds that seem to make pictures in the sky. One can make many shapes and designs by watching the clouds pass by overhead. These clouds have a flat bottom and a billowy top. The base of the cloud forms at the altitude at which the rising air cools and condensation starts.  

The remaining clouds have been named by combining terms. For example, clouds that are sheet-like yet have vertical structure are called stratocumulus.  

 

Greenhouse Effect

 

The Earth is kept warm by the atmosphere so our planet is not a frozen ball of ice. This blanket of gases reflects some of the heat from the sun (30%) and traps the rest (70%). It's the same reason why it gets so hot inside a parked car. The glass reflects some of the sunlight but traps most of it. This is called the greenhouse effect: a greenhouse is a house made of glass used in temperate areas to keep plants warm in the winter.
Carbon dioxide is the main gas responsible for the greenhouse effect. In the past, carbon dioxide was mainly produced by plants and animals as they breathe. Human activities now pump in massive amounts of atmospheric carbon dioxide by burning fossil fuels (petrol, natural gas, coal) by industries, when driving a car, in electrical generating plants; and by burning wood and burning to clear land for agriculture. Other human activities such as deforestation reduces the amount of carbon dioxide naturally removed by trees as they photosynthesise.

 

Communications and Atmosphere

 

Many communication systems utilize the ionosphere to reflect radio signals over long distances. Ionospheric storms can affect radio communication at all latitudes. Some radio frequencies are absorbed and others are reflected, leading to rapidly fluctuating signals and unexpected propagation paths. TV and commercial radio stations are little affected by solar activity, but ground-to-air, ship-to-shore, Voice of America, Radio Free Europe, and amateur radio are frequently disrupted. Radio operators using high frequencies rely upon solar and geomagnetic alerts to keep their communication circuits up and running.

 When an aircraft and a ground station are aligned with the Sun, jamming of air-control radio frequencies can occur. This can also happen when an Earth station, a satellite, and the Sun are in alignment.

Satellites

Geomagnetic storms and increased solar ultraviolet emission, heat Earth's upper atmosphere, causing it to expand. The heated air rises, and the density at the orbit of satellites up to about 1000 km increases significantly. This results in increased drag on satellites in space, causing them to slow and change orbit slightly. Unless low-Earth-orbit satellites are routinely boosted to higher orbits, they slowly fall, and eventually burn up in Earth's atmosphere.

Skylab is an example of a spacecraft re-entering Earth's atmosphere prematurely as a result of higher-than-expected solar activity. During the great geomagnetic storm of March 1989, four of the Navy's navigational satellites had to be taken out of service for up to a week.

As technology has allowed spacecraft components to become smaller, their miniaturized systems have become increasingly vulnerable to the more energetic solar particles. These particles can cause physical damage to microchips and can change software commands in satellite- borne computers.

Differential Charging. Another problem for satellite operators is differential charging. During geomagnetic storms, the number and energy of electrons and ions increase. When a satellite travels through this energized environment, the charged particles striking the spacecraft cause different portions of the spacecraft to be differentially charged. Eventually, electrical discharges can arc across spacecraft components, harming and possibly disabling them. Bulk Charging. Bulk charging (also called deep charging) occurs when energetic particles, primarily electrons, penetrate the outer covering of a satellite and deposit their charge in its internal parts. If sufficient charge accumulates in any one component, it may attempt to neutralize by discharging to other components. This discharge is potentially hazardous to the satellite's electronic systems.

Radiation Hazards to Humans

Intense solar flares release very-high-energy particles that can be as injurious to humans as the low-energy radiation from nuclear blasts. Earth's atmosphere and magnetosphere allow adequate protection for us on the ground, but astronauts in space are subject to potentially lethal dosages of radiation. The penetration of high-energy particles into living cells, measured as radiation dose, leads to chromosome damage and, potentially, cancer. Large doses can be fatal immediately. Solar protons with energies greater than 30 MeV are particularly hazardous. In October 1989, the Sun produced enough energetic particles that an astronaut on the Moon, wearing only a space suit and caught out in the brunt of the storm, would probably have died. (Astronauts who had time to gain safety in a shelter beneath moon soil would have absorbed only slight amounts of radiation.)

Solar proton events can also produce elevated radiation aboard aircraft flying at high altitudes. Although these risks are small, monitoring of solar proton events by satellite instrumentation allows the occassional exposure to be monitored and evaluated.

 

 

 

Geologic Exploration

 

Earth's magnetic field is used by geologists to determine subterranean rock structures. For the most part, these geodetic surveyors are searching for oil, gas, or mineral deposits. They can accomplish this only when Earth's field is quiet, so that true magnetic signatures can be detected. Other surveyors prefer to work during geomagnetic storms, when the variations to Earth's normal subsurface electric currents help them to see subsurface oil or mineral structures. For these reasons, many surveyors use geomagnetic alerts and predictions to schedule their mapping activities.

 

Electric Power

When magnetic fields move about in the vicinity of a conductor such as a wire, an electric current is induced into the conductor. This happens on a grand scale during geomagnetic storms. Power companies transmit alternating current to their customers via long transmission lines. The nearly direct currents induced in these lines from geomagnetic storms are harmful to electrical transmission equipment. On March 13, 1989, in Montreal, Quebec, 6 million people were without commercial electric power for 9 hours as a result of a huge geomagnetic storm. Some areas in the northeastern U.S. and in Sweden also lost power. By receiving geomagnetic storm alerts and warnings, power companies can minimize damage and power outages.

Pipelines

 

Rapidly fluctuating geomagnetic fields can induce currents into pipelines. During these times, several problems can arise for pipeline engineers. Flow meters in the pipeline can transmit erroneous flow information, and the corrosion rate of the pipeline is dramatically increased. If engineers unwittingly attempt to balance the current during a geomagnetic storm, corrosion rates may increase even more. Pipeline managers routinely receive alerts and warnings to help them provide an efficient and long-lived system.

Climate

 

The Sun is the heat engine that drives the circulation of our atmosphere. It has long been assumed to be a constant source of energy; recent measurements of this solar constant have shown that the base output of the Sun can vary by up to two tenths of a percent over the 11-year solar cycle. Temporary decreases of up to one-half percent have been observed. Atmospheric scientists say that this variation is significant and that it can modify climate over time. Plant growth has been shown to vary over the 11-year sunspot and 22-year magnetic cycles of the Sun, as evidenced in tree-ring records.

While the solar cycle has been nearly regular during the last 300 years, there was a period of 70 years during the 17th and 18th centuries when very few sunspots were seen (even though telescopes were widely used). This drop in sunspot number coincided with the timing of the little ice age in Europe, implying a Sun- to-climate connection. Recently, a more direct link between climate and solar variability has been speculated. Stratospheric winds near the equator blow in different directions, depending on the time in the solar cycle. Studies are under way to determine how this wind reversal affects global circulation patterns and weather.

During proton events, many more energetic particles reach Earth's middle atmosphere. There they cause molecular ionization, creating chemicals that destroy atmospheric ozone and allow increased amounts of harmful solar ultraviolet radiation to reach Earth's surface. A solar proton event in 1982 resulted in a temporary 70% decrease in ozone densities.

Biology

 

There is a growing body of evidence that changes in the geomagnetic field affect biological systems. Studies indicate that physically stressed human biological systems may respond to fluctuations in the geomagnetic field. Interest and concern in this subject have led the Union of Radio Science International to create a new commission entitled Electromagnetic in Biology and Medicine.

Possibly the most closely studied of the variable Sun's biological effects has been the degradation of homing pigeons' navigational abilities during geomagnetic storms. Pigeons and other migratory animals, such as dolphins and whales, have internal biological compasses composed of the mineral magnetite wrapped in bundles of nerve cells. While this probably is not their primarily method of navigation, there have been many pigeon race smashes, a term used when only a small percentage of birds return home from a release site. Because these losses have occurred during geomagnetic storms, pigeon handlers have learned to ask for geomagnetic alerts and warnings as an aid to scheduling races.

Conclusion


Atmospheric conditions has a close link with all our activities on earth including, Aeronautics, Space travel, Astronomy studies and the Weather on earth. That way atmospheric science has become a major subject of study.


Climate change could drive a million of the world's species to extinction as soon as 2050, a scientific study. The authors say in the Journal Nature, a study of six world regions suggested a quarter of animals and plants living on the land could be forced into oblivion. Dr Klaus Toepfer, the head of the United Nations Environment Programme, said: "If one million species become extinct... it is not just the plant and animal kingdoms and the beauty of the planet that will suffer. "Billions of people, especially in the developing world, will suffer too as they rely on Nature for such essential goods and services as food, shelter and medicines".

For over 100 years, scientists have grappled with the cause of "background" extinction. Human beings are currently causing the greatest mass extinction of species since the extinction of the dinosaurs 65 million years ago. Over 99% of all the species that ever lived on Earth have already disappered. The majority may slip away quietly and without any fanfare.

Because of accelerating technological progress, humankind may be rapidly approaching a critical phase in its career. Of course extinction is a natural process. The gradual process of adaptation takes place over thousands of years. Extinctions in the past were triggered by climatic changes or other geological forces. Previously, the rate of extinction is estimated at 10 species per century. However, today, extinctions are happening very rapidly and are due mainly to human activity. The current extinction rate is estimated at 50-100 species of per DAY. And extinction is forever.Does the high rate of extinction really matter? After all humans only rely on a small range of plants and animals and the rest of the species are not useful anyway. Can we keep a closed eye?

 

For few million years, Planet earth has been going through a phase of supporting life in the form we see around us. Every good thing must come to an end, sooner or later. The life on earth is no exception. The question is how long living being would survive on this planet? It is defiantly few million years. But the uncontrolled human population growth and the unnatural living style is changing the environment fast and bring the life on earth closer to extinction by  few million years than what nature has provided for. It is our responsibility to extend this period. Towards this end, this article attempts to increase general awareness about the Atmosphere.

 

Every species seems to come and go. Some last longer than others, but nothing lasts forever. Humans are a relatively recent phenomenon, jumping out of trees and striding across the land around 200 000 years ago. Will we persist for many millions of years to come, or are we headed for an evolutionary makeover, or even extinction? According to Reinhard Stindl, of the Institute of Medical Biology in Vienna, the answer to this question could lie at the tips of our chromosomes. In a controversial new theory he suggests that all eukaryotic species (everything except bacteria and algae) have an evolutionary "clock" that ticks through generations, counting down to an eventual extinction date. This clock might help to explain some of the more puzzling aspects of evolution, but it also overturns current thinking and even questions the orthodoxy of Darwin's natural selection.


 

Reference Links
 

  • SPACE WEATHER

      Current Conditions
      This site is sponsored by Science@NASA. Space weather and other forecasts that appear here are formulated by Dr. Tony Phillips - Solar Wind speed, SUNSPOT WATCH, X-ray Solar Flares, COMETs, CRESCENT VENUS, What's Up in Space today, Forecasts
  • SPACE WEATHER FROM NASA

      The Space Environment Center provides real-time monitoring and forecasting of solar and geophysical events, conducts research in solar-terrestrial physics, and develops techniques for forecasting solar and geophysical disturbances. SEC's Space Weather Operations Center is jointly operated by NOAA and the U.S. Air Force and is the national and world warning center for disturbances that can affect people and equipment working in the space environment.
  • Solar Events Database

      SolarSoft Latest Events Archive, quite detailed information made available.
  • Standard Atmosphere Calculator

  • Standard Atmosphere Computations
  • Standard Atmosphere Calculator
  • This is an interactive program in which you can investigate changes in the atmosphere

  • Interactive Program Downloads

  • Interactive Kite Modeler
  • STANDARD ATMOSPHERE (TROPOSPHERE)

  • This weather calculator converts temperature, wind, pressure, heat index and more.

  • A Sea Water Equation of State Calculator

  • Glossary of Terms Atmospheric Science

  • Atmospheric Physics: Database of Institutions

  • The Atmospheric Physics Group-Toronto

  • The Atmospheric Physics Group

  • The Atmospheric Physics group-UK

  • The Atmospheric Physics Group- Germany

  • The Atmospheric Physics Group at Adelaide

  • Institute for Physical Science and Technology at the University of Maryland

  • This atmospheric research group-Canterbury

  • University of Pittsburgh: Space and Atmospheric Physics Group

  • Space & Atmospheric Physics Group of UK
  • Space Physics Group at the University of Houston

  • Atmospheric Physics at MISU

  • The Radio Science Center for Space and Atmosphere (RASC) - Japan

  • The Institute of Atmospheric Physics - Czech Republic

  • ATMOSPHERIC SCIENCES AND AERONOMY

  • The INO Collaboration

  • Space & Atmospheric Group - Imerial College London

  • PUBLICATIONS