Why are Hill Stations COOLER??

           Small kids often ask this question when they visit a HILL STATION. Why is it Cool here? We are closer to the SUN now??  This question may sound stupid but we struggle to answer it.

            The drop in temperature at Hill Stations and Mountains is because of the  change in ATMOSPHERIC PRESSURE. There is a relation between PRESSURE and TEMPERATURE. Both Pressure and Temperature vary proportionally. This is what THERMODYNAMICS says. But I hate equations and formulas. Let's have a practical explanation and good understanding of this FACT

        There are two FACTS why the Hill Stations are COOLER.
                         1. Drop in Pressure as we climb up the HILL and
                         2. The Amount of WATER VAPOUR content.
          Lets see how the PRESSURE DROP and amount of WATER VAPOUR affect the TEMPERATURE.
            The cause of the ATMOSPHERIC PRESSURE will let us know the reason for this fall in Pressure with increase in Altitude. The word PRESSURE is the extension of the word PRESS. The surface of our EARTH is PRESSED up by the AIR present above the Surface. We know that AIR has mass and so it is PULLED down to the Surface by GRAVITY. The Weight of the Air acts all over the Surface and exerts a pressure ( a force). This Pressure is atmospheric Pressure.
           Gravity plays an Important role in this. Gravity is maximum at sea level and it decreases when we move up.As we climb up the hill, the Gravity decreases so the Atmospheric Pressure decreases.

            The Drop on Pressure decreases TEMPERATURE. This is because when the pressure increases, more number of particles or molecules are contained in the space. Every particle possess some Heat. When the number is more, the heat possessed by all the particles together is more.Also the collisions between these molecules is more which produces heat.When Pressure decreases, the molecules spread out and so the HEAT is not concentrated so the TEMPERATURE goes down.

            The Atmospheric Pressure is WEIGHT of AIR which is a product of GRAVITY. At sea level, the atmospheric pressure is more and in a HILL STATION the Atmospheric pressure is comparatively  LESS. As Pressure decreases ,the Temperature also Decreases.

           The next FACT is the presence of WATER VAPOUR. Water Vapour constitutes for 36-70% of GREENHOUSE GASES.Water Vapours absorb heat from the SUN and make the surrounding WARM. This is at GROUND LEVEL. At Higher Altitudes, these water vapours condense due to decrease in Pressure and form MIST which are suspended water particles. The water vapour present at HILL STATIONS is LESS so there is less absorption of HEAT from the SUN which prevents the rise of temperature.
           My Conclusion is, Temperature don't decrease on climbing up. INSTEAD it can be said that the Atmospheric Temperature increases towards the Surface of earth because of WATER VAPOUR and other GREENHOUSE GASES.

GRAVITY is the ROOT CAUSE for the change in TEMPERATURE.


nadinarayanan said...

good answer suriya...

Anonymous said...

i like ur explanation

jas kaur said...

ur way of explaination is best

Unknown said...

Excellent explanation


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