Structure of the Atmosphere

Define air. And arrange the gases in decreasing order of their abundance in the troposphere.

Air can be defined as a mixture of gases.

N>O>Ar>CO2>Ne>He>H

Name the different layers of atmosphere from bottom to top.

Troposphere

Stratosphere

Mesosphere

Thermosphere(Made up of ionosphere and exosphere)

Write down the key points about troposphere.

1)All the meterological activities take place in this layer.

2)99 percent of gases of the atmosphere are concentrated here.

3)With altitude, temperature decreases.(6.5 degree C per 1 km)

4)Thickest at the equator and thinnest at the poles.

Why are the gases concentrated near the surface of the Earth?

Because of gravitational force of earth.

Why is the troposphere thickest at the equator and thinnest at the poles?

1)Equator receives the highest insolation. The gas molecules undergo thermal expansion.

2)The gravitational force is weaker at the equator than at the poles. This causes gases to be closer to the surface at poles and farther from the surface at the equator.

3)Air converges and rises near the equator while air sinks at the poles.

Why does the temperature decrease as we go up in the troposphere?

The heat is trapped by the gases and the concentration of gases is highest near the surface.

As we go up, the concentration of gases keeps decreasing and so does the temperature.

Proof that temperature decreases as we go up.

Mt Kilimanjaro, despite being at the equator has snow caps on it beyond a certain altititude.

This shows that , if altitude is really high, then even the hottest zone of Earth can be covered with snow.

What is the role of anthropogenic activites in global warming?Why do we plant trees?

Vehicular and industrial emmissions, stubble burning, deforestation contribute to an increase in the greenhouse gases in the atmosphere. This leads to global warming.

-We plant trees as forests , or a single plant for that matter take in CO2 while carrying out photosynthesis.

-Forests act as CO2 sinks.

At which latitude, does the upper limit of atmosphere has the lowest temperature?

At the equator. Because the thickness of the troposphere is 18 kms at the equator whereas the thickness of the same at poles is 8 kms.

On applying NLR, on would find out that the uppermost limit of troposphere at the equator has a temperature of about -60 degree celsius.

And the same at poles would be -40 degree celsius.

What is the average thickness of the troposphere?

13 kms.

Write down the key points about the stratosphere.

1)It contains ozone

2)It is the layer in which aeroplanes fly.(no turbulence)

3)Temperature increases with height.

4)It extends till a height of 50 km.

Why does the temperature increase with height in stratosphere?

Because the ozone layer is present.

The incoming ultraviolet rays interact with the ozone and break it down to O2+O.

So, the heat is absorbed in this layer by the ozone.

Ozone layers protect us from ultraviolet rays. How?

The ultraviolet rays fails to penetrate the ozone layer.

All the energy is used up in breaking down the ozone.

When night sets in, the O2+O combine to form Ozone again.

This ozone again protects the Earth from ultraviolet rays in the next day.

Which element is responsible for ozone depletion? or ozone hole?How?

Cl

The Cl bonds with the O that is formed due to interaction of ultraviolet rays with O3.

This leaves the O2 isolated and shuts down the scope for formation of ozone on the upcoming day.

Simply put, the Cl causes destruction of Ozone.

Write down the key points of mesosphere.

It is the coolest layer of atmosphere.

Temperature decreases with increase in height.

Temperature becomes as low as -90 degrees.

50-80 kms.

The meteors coming in start burning at this layer.

Why does the temperature decrease with height in the mesosphere?

Due to low concentration of gases.

Why do meteors begin burning at mesosphere and not before it?

The thermosphere has very little gas molecules. The mesosphere, on the other hand has relatively higher concentration of the same. The meteors on coming in contact with these gases experience frictional force and are set on fire!

Write down the key points of thermosphere.

Temperature increases with height.

It is divided into two layers , with one layer containing charged particles and the other layer, vacuum.

The former is called ionosphere and the latter, exosphere.

The radiowaves are refracted back to the Earth from the ionosphere.

The upper layer is called the exosphere and it connects the atmosphere with space.

It is almost devoid of gases.

Division of ionosphere