Climatology

Climatology is the scientific study of climate. It is a branch of the atmospheric sciences concerned with the description of the climate, the analysis of the causes of climatic differences and changes and their practical consequences.

Structure, Composition of Atmosphere :

What is Atmosphere ?

The air surrounding the Earth is called the atmosphere.
The atmosphere is an integral part of our Earth.
It is connected with the earth due to the gravitational force of the earth.
It helps in stopping the ultra violet rays harmful for the life and maintain the suitable temperature necessary for life.
The air is essential for the survival of all forms of life on the earth. One cannot imagine any kind of life in the absence of it. The atmosphere is like a large protective cover.
Besides many gases, water vapour and dust particles are also found in the atmosphere.

Structure of Atmosphere

Thermal Zone Segregation

Troposphere

Lowermost layer of the atmosphere.
Also known as convective region(all convection occurs till the Tropopause).
Tropopause: Zone separating the troposphere from stratosphere. The temperature here is nearly constant.
- Average height = 13 km
- Highest at equator (18 km) because heat is transported to great heights by strong convectional currents
- Lowest at poles (8 km)
The temperature is also lowest at equator (-80ºC) as compared to poles (-45ºC). This is because convectional currents are strongest at equator.
90% of total mass.
Contains dust particles and water vapor.
Most cloud appear here as approx 99% of water vapor is found here.
All changes in climate and weather take place in this layer.
Seasons and jet streams affect troposphere.
Most important layer for all biological activity.
Temperature reduces at 6.5ºC/km or 1ºC▼/165m (normal lapse rate) as we move up.

Stratosphere

Extends from tropopause to 50 km.
Important Feature = It contains the Ozone Layer (Shields life on the earth by absorbing intense, harmful ultra-violet radiation)
Temperature inversion: Normal Lapse Rate ends This warming of the stratosphere with altitude is caused largely due to absorption of solar energy by ozone.
The air movements are almost horizontal. This is because the effect of convection currents is almost negligible in comparison to troposphere. This in turn prevents vertical mixing of pollutants from troposphere to stratosphere.
Ideal region for flying jets as clouds are almost absent (sometimes layer possess cirrus clouds in lower level).
Winds blow from west to east.

Mesosphere

Ranges 50-80 km (Stratopause and Mesopause)
Temperature again starts falling with elevation (because no GHGs exists here, i.e. no heat absorbing layer nor ozone layer).
- Temperature decrease from 0 ºC to -90 ºC.
Meteors burn in this layer.
- Mesospheric or Noctilucent clouds visible at high latitude during summer season due to the condensation of moisture around the meteoric dust.
Mesopause= Upper limit of mesosphere
Very thin layer causes difficulty in breathing.

Thermosphere

It extends from 80-400 km and contains electrically charged particles known as ions (Region is known as Ionosphere).
Temperature rises with height again due to proximity to the sun (Ions absorbs heat).
- Even though the temperature is high but because of rarified atmosphere the heat could not be felt.
International Space Station&Satellitesorbit in this layer
Aurorasalso form in this layer.

Exosphere

Uppermost layer of the atmosphere.
Above the thermosphere.
Highest layer and extremely rarefied.
It gradually merges with the outer space.

Functional Zone Segregation

Ozonosphere

1. It spans the stratosphere and lower mesosphere and lies at an altitude between 30 km and 60 kmfrom the earth’s surface.
2. This layer reflects the harmful ultraviolet radiation due to the presence of ozone molecules.
3. The ozonosphere is also known as chemospherebecause of immense chemical activity goes on here.
4. The temperature increases at a rate of 5°C/km.