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THE FIVE SPHERES OF THE ATMOSPHERE (PLUS A BONUS)

They are: The Exosphere the thermosphere, the mesosphere, the stratosphere, and the troposphere.

1. THE EXOSPHEREThe top of the exosphere is generally marked at 6,200 miles above sea level

There is so little density of particles in the exosphere that it can be difficult to determine where exactly the exosphere actually ends and outer space begins

Because the air in the exosphere is extremely thin, temperatures range quite drastically.

It is in the exosphere that satellites orbit; in this environment, there is very little friction as compared to lower levels of the atmosphere, meaning it is the perfect place for equipment such as satellites to orbit

Some scientists actually consider the exosphere as part of outer space

In the most technical sense, the upper limit of the exosphere is the last point at which Earth’s gravity still has any influence on particles

The boundary could be anywhere from 6200 miles above the earth to as far as 120,000 miles, depending on which scientist is defining the exosphere.

AND NOW, THE BONUS: THE IONOSPHERE

The ionosphere occupies the space between the thermosphere and the exosphere

The outer edge of the Earth's atmosphere is subjected to extremely harsh solar radiation which consists of a broad frequency spectrum. A neutral oxygen atom, under the effect of ultraviolet radiation, loses an electron and disintegrates into an ion. This positively charged oxygen ion is highly unstable and agitated. These ions tend to attract the free electrons when they are at close proximity. The upper levels of this layer have lesser ions compared to the lower levels. Therefore, the process of ionization and recombination is greater at lower levels. This leads to the formation of this highly unstable layer of the Earth's atmosphere.

D layer (lowest) absorbs the highest amount of harsh x-ray radiation

E layer can reflect frequencies ranging from 10-50 MHz

F layer mostly absorbs ultraviolet rays. This layer splits into two layers during the day. These are referred to as F1 and F2. This layer facilitates high frequency wave transmission.

THE CHANGING IONOSPHEREDuring the day, the ionosphere is thicker than at night, due to the sun’s rays causing more interactions. So, radio waves travel higher at night and bounce farther away. This is why AM radio stations can frequently be heard a thousand miles away at night.

AURORA BOREALIS: THE NORTHERN LIGHTS

The Northern Lights, or aurora borealis, are bright dazzling displays in the sky that occur when gaseous particles collide. They can be seen from many places on Earth but are visible nearly every night nearer to the North Pole.

Auroras occur when charged particles from the sun's solar wind interact with Earth's magnetic field (at altitudes above 50 miles, or 80 km). During intense solar storms, the Northern Lights become more spectacular and can sometimes be visible as far south as Texas

The colors in an aurora are caused when oxygen and nitrogen particles mix with the charged particles in the atmosphere. The colors depend on what gas is involved and how high in the ionosphere the reaction takes place.

2. THE THERMOSPHEREThe thermosphere roughly begins at a distance of 53 to 56 miles from the surface of the planet, and extends all the way up to 311 to 621 miles.

In the lower half of the thermosphere, the temperature increases very quickly with altitude. It is only after reaching a point that it becomes stable. In the upper thermosphere, its temperature ranges 932°F to 3,632°F. The temperature here, is highly dependent on solar activity, and can reach 3,630°F or higher when solar activity is at its peak.

In the thermosphere, the atmospheric pressure is greatly reduced when compared to the atmosphere at Earth's surface. At these high altitudes, the atmospheric gases tend to sort into layers according to their molecular mass, and chemical reactions happen much faster here than near the surface of the earth.

THE MESOPAUSEThe mesopause is the temperature minimum at the boundary between the mesosphere and the thermosphere atmospheric regions.

Due to the lack of solar heating and very strong radiative cooling from carbon dioxide, the mesopause is the coldest region on Earth with temperatures as low as -100°C (-146°F or 173 K).

The altitude is estimated to be between 52 miles and 100 miles above the earth.

3. THE MESOSPHEREIt literally means 'middle sphere' and is derived from the Greek words "mesos", meaning middle and "sphaira" which means ball.

The most important function of mesosphere is the destruction of the meteors that fall on earth.

The composition of air in the mesosphere includes oxygen, nitrogen and carbon dioxide.

These meteors collide with the gas particles present in the mesosphere and burn. We call them as 'shooting stars' and make a wish.

The higher up we go in the mesosphere, the more the temperature decreases. This happens due to the decreasing solar heat and increasing cooling due to radiative emission of carbon dioxide. The temperature in the mesosphere varies according to the latitude and the seasons. The minimum temperature in mesosphere is -90ºC or -130ºF! This is at the highest region in mesosphere and also the coldest place on earth!

THE STRATOPAUSEOn Earth, the stratopause is 50 to 55 kilometers (31–34 miles) high above the Earth's surface.

The temperature in the stratopause is -15 degrees Celsius (5 degrees Fahrenheit).

4. THE STRATOSPHERE

At moderate latitudes the stratosphere is situated between about 10–13 km (33,000–43,000 ft; 6.2–8.1 mi) and 50 km (160,000 ft; 31 mi) altitude above the surface, while at the poles it starts at about 8 km (26,000 ft; 5.0 mi) altitude, and near the equator it may start at altitudes as high as 18 km (59,000 ft; 11 mi).

The stratosphere is layered in temperature because ozone (O3) here absorbs high energy UVB and UVC energy waves from the Sun and is broken down into atomic oxygen (O) and diatomic oxygen (O2).

Commercial airliners typically cruise at altitudes of 9–12 km (30,000–39,000 ft) in temperate latitudes (in the lower reaches of the stratosphere).

The layer constitutes about 24% of the total atmosphere. And it contains about 19% of the atmospheric gases.

There is no uniformity in the stratosphere if the temperature is considered. This is because of the presence of ozone layer at the top region. The temperature at the top of stratosphere is around 270 K (-3°C or 29.6°F). The temperature in the middle and lower region is less as the UV rays do not reach there.

THE TROPOPAUSE

The layer between the troposphere and the stratosphere.

Commercial airlines generally fly above this layer to avoid storms.

The height of the tropopause varies greatly. In hotter areas, the height is greater, and in cooler areas, it is much lower.

5. THE TROPOSPHERE

Contains about 70 to 80 per cent of the total mass of the Earth's atmosphere and 99 per cent of the water vapor.

In the troposphere, air temperature on average decreases with height at an overall positive lapse rate of about 6.5°C/km , until the tropopause is reached.

The troposphere is 10 miles from the equator, and is 5-7 miles above the poles

Does not contain ozone

Sunlight comes from the top to the bottom of the atmosphere, but the troposphere is primarily heated from the bottom. This is because the surface is much better at absorbing a wide range of solar radiation as compared to the air.

MAJOR COMPONENTS OF THE ATMOSPHERE

Nitrogen and oxygen make up about 99% of the atmosphere. Carbon dioxide is present in small amounts, but contributes a significant role in heating the atmosphere by absorbing energy.

EARTH’S MOTIONS

Rotation – the spinning of Earth about its axis.

Revolution – the movement of Earth in its orbit around the sun.

EARTH’S ORIENTATION

Seasonal changes occur because Earth’s position relative to the sun continually changes as it travels along its orbit.

The earth’s axis is tilted 23.5 degrees from the perpendicular. The axis remains pointed toward the North Star as Earth moves around the sun. This means the angle of the noon sun may vary up to 47 degrees for many locations during the year.

SOLSTICES AND EQUINOXES

June 21 is called the summer solstice in the Northern Hemisphere and simultaneously the winter solstice in the Southern Hemisphere. Around December 21 the solstices are reversed and winter begins in the northern hemisphere.

On June 21, there are 24 hours of daylight north of the Arctic Circle (66.5° north of the equator) and 24 hours of darkness south of the Antarctic Circle (66.5° south of the equator). The sun's rays are directly overhead along the Tropic of Cancer (the latitude line at 23.5° north, passing through Mexico, Saharan Africa, and India) on June 21.

On the equinoxes (September 22 or 23 – Autumnal and March 21 or 22 – Spring), the vertical rays of the sun strike the equator. This causes the day and night to be approximately 12 hours each.

HEATING THE ATMOSPHERE

Heat is the energy transferred from one object to another because of a difference in their temperatures.

Three mechanisms of energy transfer as heat are conduction, convection, and radiation.

CONDUCTION

Conduction is the transfer of heat through matter by molecular activity.

Metals are good conductors. Ever touch a spoon that has been sitting in a hot pan?

Since air is a poor conductor, conduction is the least important mechanism of heat transfer for the atmosphere.

CONVECTIONConvection is the transfer of heat by mass movement or circulation within a substance.

RADIATION

Radiation travels out in all directions from its source. Unlike conduction and convection, radiant energy can travel through the vacuum of space.

Four laws that govern radiation:

1. All objects, at any temperature, emit radiant energy.2. Hotter objects radiate more total energy per unit area than colder objects do.3. The hottest radiating bodies produce the shortest wavelengths of maximum radiation.4. Objects that are good absorbers of radiation are good emitters as well.

SOLAR RADIATIONWhen radiation strikes an object, there are usually three different results. 1. Some energy is absorbed by the object.2. Substances such as water and air are transparent to certain wavelengths of radiation.3. Some radiation may bounce off the object without being absorbed or transmitted.

REFLECTION AND SCATTERINGInteraction that changes direction of lightReflection from surfaces

Radiation redirected away from surface without being absorbedReflected light makes objects visibleWavelength-dependent reflection sensed as color differences

Specular reflectionCoherent beam reflected - images preservedMirrors, shiny metal and smooth water surfaces

ScatteringLight reflected in all directions - images not preserved

Fogged mirror (water droplets) scatter at different angles, so can't see anything in mirrorComparable effect with fog on glass scattering transmitted light

Atmospheric molecules and aerosols scatter incoming solar radiation

ABSORPTION

Radiant energy is converted into internal energyCeases to exist as radiant energyHeats atmosphere directly

Very little absorption in visible wavelengthsOzone absorbs most ultravioletCO2, water vapor and water droplets absorb near infrared

WHY DO TEMPERATURES VARY?Factors other than latitude that exert a strong influence on temperature include heating of land and water, altitude, geographic position, cloud cover, and ocean currents.

COMPARISON OF VANCOUVER AND WINNIPEG: LAND AND WATER

Land heats more rapidly andto higher temperatures than water. Land also cools more rapidly andto lower temperatures than water.

Vancouver, British Columbia, islocated along the windward Pacific coast. Winnipeg, Manitoba, is far from the influence of water. Both cities are at about the same latitude, so they experience similar lengths of daylight and angles of the sun’s rays. Winnipeg, however, has much greater temperature extremes than Vancouver does. Vancouver’s moderate year-round climateis due to its location by the Pacific Ocean.

QUITO AND GUAYAQUIL, ECUADOR

ALTITUDE

Both cities are near the equator and relatively close to one another.The annual mean temperature at Guayaquil is 25°C, compared to Quito’s mean of 13°C. If you note these cities’ elevations, you canunderstand the temperature difference.Guayaquil is only 12 meters above sea level, whereas Quito is high in the Andes Mountains at 2800 meters.

EUREKA, CALIFORNIA VS. NEW YORK CITY GEOGRAPHIC POSITION

A coastal location where prevailing winds blow from the ocean onto the shore (a windward coast) experiences considerably different temperatures than does a coastal location where the prevailing winds blow from the land toward the ocean (a leeward coast). In the first situation, the windward coast will experience the full moderatinginfluence of the ocean—cool summers and mild winters, compared to an inland station at the same latitude. In contrast, a leeward coast will have a more continental temperature pattern because winds do not carry the ocean’s influence onshore. Eureka, California, and New York City illustrate this aspect of geographic position. The annual temperaturerange in New York City is 19°C greater than Eureka’s range.

CLOUD COVER AND ALBEDOAlbedo is the fraction of total radiation that is reflected by any surface. Many clouds have a high albedo, and therefore reflect a significant portion of the sunlight that strikes them back to space.

The extent of cloud cover is a factor that influences temperatures in the lower atmosphere. By reducing the amount of incoming solar radiation, the maximum temperatures on a cloud-covered day will be lower than on a day when the clouds areabsent and the sky is clear, as shown in Figure A. At night, clouds have the opposite effect, as shown in Figure B. Clouds act as a blanket by absorbing outgoing radiation emitted by Earth and reradiating a portion of it back to the surface. Thus, cloudynighttime air temperatures do not drop as low as they would on a clear night. The effect of cloud cover is to reduce the daily temperature range by lowering the daytime maximum and raising the nighttime minimum.