Insolation — Geography STD 9 — Question

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.