Geography [3 Mark Question Answer]

The temperature decreases with height at the rate of 1°C per 165 metres or about 0°C per kilometre. The atmosphere is heated by radiation from the earth below. Therefore, lower layers are warmer than higher layers. There is an absence of water vapour and dust particles on high mountains. So there is unchecked radiation. That is why mountains are cooler than plains. Shimla is cooler than Delhi. Similarly, Nainital is cooler than Allahabad.

The difference between the maximum and minimum temperature recorded on a particular day at a place is called a daily range of temperature. It is low in coastal areas while it is high in deserts and in the interiors of continents.
The difference between the mean temperature of the hottest month (July) and the mean temperature of the coldest month is called the annual range of temperature. It is a low equatorial region, while it is high in polar areas.

The Northern Slopes of Himalayas is away from the Sun. These slopes get oblique rays. These slopes are exposed to cold winds. These are shady slopes and are cooler. But the Southern Slopes are Sun facing slopes. These get Sun’s rays more directly and also for longer periods. These are Sunny slopes and shelters from cold winds. So the Southern Slopes of Himalayas are warmer than northern slopes.

Vertical rays are hotter than slanting rays due to the following reasons:

• Vertical rays heat up a smaller surface. Hence, the heat received per unit of area is large. On the other hand, slanting rays heat up a large area.
• Vertical rays travel through a shorter distance in the atmosphere and the loss of heat is less. Slanting rays travel a longer distance through the atmosphere where much of its heat is absorbed by clouds, water vapour, and dust particles.

Insolation is the incident solar radiation onto some object. Tropical region gets vertical rays of the sun and receives much heat providing high temperature while the temperate and polar regions have less temperature due to slanting rays of the sun. The vertical rays are concentrated in one region and the slanting rays are spread in a large area, that's why the sun gives more insulation to vertical ray