- No. 2.Give the characteristics of troposphere. Why temperature decreases upwards in this sphere?
Answer. Followings are the characteristics of troposphere.
(i) Troposphere is lowest region of the atmosphere.
(ii) It extends from the surface of the Earth up to 12 km.
(iii) In this region temperature decreases from 17°C to -58°C i.e. at the rate of about 6°G per Km.
(iv) The major constituents of troposphere are nitrogen and oxygen gases that constitute 99% by volume of the Earth’s atmosphere.
(v) In this region all weathers occurred almost all aircrafts fly in this region.
Decreasing of temperature upwards
Although concentration of carbon dioxide and water vapours is negligible in atmosphere, yet they play a significant role in maintaining temperature of the atmosphere. Both of these gases allow visible light to pass through but absorb infrared radiations emitted by the Earth’s surface. Therefore, these gases absorb much of the outgoing radiations and warm the atmosphere. As the concentration of gases decreases gradually with the increase of altitude, correspondingly temperature also decreases at a rate of 6 K per kilometer.
- No. 3.What is the characteristics of stratosphere? Why temperature increases upwards in this sphere?
Answer. Following are characteristics of stratosphere,
- Stratosphere lies above the troposphere,
(ii) It extends from 12 km to 50 km,
(iii) In this region temperature increases from -58°C to 20.i.e. there is gradual increases of temperature by 60°C.
(iv) This region is further subdivided into three regions; lower, middle and upper region.
(v) Ozone gas is found in this region which is responsible for the rise of temperature in this region.
(vi) Ozone layer is formed in middle of the stratosphere.
This region is next to troposphere and extends up to 50 kilometers. In this region, temperature rises gradually up to 2 °C. The presence of ozone (due to absorption of radiation) in this region is responsible for the rise of temperature in stratosphere. Within this region, temperature increases as altitude increases, such as lower layer temperature is about -58 °C and upper layer is about 2°C. Thus, stratosphere is layered in temperature as shown in figure.
Since ozone in the upper layer absorbs high energy ultraviolet radiations from the Sun, it breaks down into monoatomic arid diatomic oxygen O2 .This phenomenon results in increasing of temperature. The mid stratosphere has less UV light passing through it. Here O and O2 recombine to form ozone which is an exothermic reaction. Thus temperature of mid stratosphere is also higher than low stratosphere. The lower stratosphere receives very low UV radiations. Because of it temperature of this layer is lowest of the above layers.