Download Atmosphere

Atmosphere
Atmosphere is the blankeet of gases around the Earth.
Contents of the atmosphere:
The atmosphere may be broadly divided into 2 vertical regions. The lower region, called the
homosphere extends from the surface 80 to 100km above the Earth and has a more or less uniform
hemical composition. The upper region is the heterosphere.
The homosphere is more important of 2 atmosphere regions for human beings, because we live in it.
Homosphere has 3 groups of components: constant gases, variable gases & impurities
Constant gases: 2 major constant gases make up 99% of air. They are NITROGEN, which constitutes
78% of the air and OXYGEN accounts for an other 21% and ARGON- less than 1%.
Variable gases: All of the variable gases are in the atmosphere in small amounts. 3 of these variable
gases are essential to human well- being: CARBON DYOXID (CO2), WATER VAPOUR and
OZONE (O3)
The atmosphere has a layered structure. It consists of troposphere, stratosphere, mesosphere,
thermosphere and exosphere. Boundaries between individual layers are not sharply defined.
The troposhere is the atmosphere zone in which we live, and the layer where almost all weather
happens. In the troposhpere is nearly 80% of the atmosphere´s total mass. The troposphere contains
the great majority of the atmosphere´s water vapour. Consequently it contains nearly all clouds. The
dominant vertical characteristic of the troposphere is a rather rapis decrease in temperature with
increasing altitude. The tropopause is positioned at an average height of about 12km. Lowest is it over
the poles- about 8km and highest above to equator- about 16km.
Second thermal layer is stratosphere- extends from the tropopause to an altitude of 50km. The lower
stratosphere up to 32 km in altitude remains constant in temperature, but above this level a gradual
temperature rise accurs. This is caused by the abscription of solar ultraviolet radiation by ozone, which
converts this energy into heat. The stratosphere is characterized by cloud less & dry air. Jet aircraft
often flies through the lower stratosphere, because it provides the easiest flying conditions. Thermal
boundary is stratopause- the temperature stops rising and begins falling as the atmosphere´s third
thermal layer.
The mesosphere is entered. The mesosphere is located between 50 and 100km above the Earth´s
surface. At the upper boundary of the mesosphere, termed the mesopause
The thermosphere is found above 100 km and continues to the edge of space above 60 000km above
the surface. Temperature rises spectecularly in this layer and reaches 900°C. At 350km ionization is
also in termosphere. Ionization causes AURORA BOREALIS in the north hemisphere and
AURORA AUSTRALIS in the southern hemisphere.
Movement of air
The main function of the air is circulation. The most important function of the circulation of the air is
to redistribute heat and moisture around the world. Without it, hot places would get hotter and
hotter, and cold places would get colder and colder.
4 causes of the circulation of the air
1. atmosphere pressure- differences of the pressure are eqalized by movement of the air
2. wind
3. heat imbalances
4. rotation of the Earth
Atmosphere pressure- held to Earth by gravity. The weight of the air pushes against the Earth´s
surface and produces pressure. The air pressure at sea level is 1013 mB(mili bars). Air usually moves
from area of high pressure to area of low pressure
Italian scientist Torricelli made pressure measuring instrument known as a barometer.
Cyclones- large weather systems that rotate anticlockwise in the northern hemisphere and
clockwise in the southern hemisphere. At the center of the cyclons is Low pressure.
Anticyclones- at the center of anticyclones is High air pressure spins in the opposite direction
from a cyclones
Coriolis force- the force that owing to the rotation of the Earth, tends to deflect all objects moving
over the surface of the Earth away from their original path in the absence of any other forces.
The deflection is
to the RIGHT in N hemisphere
to the LEFT in S hemisphere