Why do we feel cold at higher altitudes when actually we are closer to the sun?
R. KISHORE
Chennai
The distance of the Sun from us is about 150 million km. Going closer to it by a few km will not have any noticeable effect. One of the main factors which determines the air temperature is how much sun’s radiation (heat energy) is absorbed by the air.
The atmosphere is mostly heated through reflection by the surface of the earth below and not directly by the Sun from above, even though the upper atmosphere is closer to the Sun, which explains why the air temperature is higher closer to Earth’s surface. Another factor is the air pressure.
At higher altitudes, it is well known that air is much thinner as compared to sea level as the air pressure becomes less and less as we go up. At sea level, the air pressure is 14.7 psi, at 10000 ft above, it is 10.2 psi and at 30000 ft, it is only 4.3 psi.
The air is thinner in the same ratio and so is the amount of heat energy available in the atmosphere around. That is the main reason why we feel cold at higher altitudes.
Third factor responsible for higher temperature near Earth’s surface is the amount of heat emitted by Earth’s surface during the nights. A larger portion of this energy is absorbed by the air layer closer to the Earth’s surface resulting in higher temperature.
S.P.S. JAIN
Former Member, Engineering, Indian Railways
Greater Noida, Uttar Pradesh
