KERALA PSC / PHYSICAL GEOGRAPHY / STRUCTURE OF ATMOSPHERE / NOTES / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE

 

KERALA PSC / PHYSICAL GEOGRAPHY / STRUCTURE OF ATMOSPHERE / NOTES / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE

KERALA PSC / PHYSICAL GEOGRAPHY / STRUCTURE OF ATMOSPHERE / NOTES / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE

·      The Atmosphere is divided into layers according to major changes in temperature. 99% of the total mass of the atmosphere is below 32 kilometers. Atmosphere can be classified into five main layers. Troposphere, Stratosphere, Mesosphere, Thermosphere (Ionosphere) and the Magnetosphere. Troposphere – 0 to 12 km, Stratosphere – 12 to 50 km, Mesosphere – 50 to 80 km, Thermosphere – 80 km and up. Thermosphere contains Ionosphere and Exosphere.

·      Troposphere is the lowest layer of the atmosphere and extends roughly to a height of 7 to 8 km near the poles to some 16km over the equator. The thickness is greater at the equator, because the heated air rises to greater heights

·      Temperature decreases with height in this layer roughly at the rate of 1ºC per 165 meters, which is called normal laps rate.

·      All weather phenomena are confined to troposphere

·      Upper limit of the troposphere is called tropopause

·      Stratosphere is a region of uniform temperature extending from an altitude of about 12km above the earth to a height of nearly 50 km. It is free from water vapour, clouds and dust.

·      The upper part of the stratosphere has plenty of ozone which affords protection to human beings on the earth against the fatal effects of ultraviolet radiations.

·      The Stratosphere also provides ideal conditions for flying aeroplanes. The upper limit of this layer is called stratosphere

·      Mesosphere is a very cold region above the stratosphere which extends from 50 or 80 km above the earth’s surface

·      Within the mesosphere the temperature decreases with altitude from about 0ºC at stratosphere to about  -100ºC at mesopause. Mesopause is the boundary line between ionosphere and mesosphere

·      Thermosphere is the uppermost layer of the atmosphere extending from the mesopause at an altitude of about 85 kms to the outer limits of atmosphere

·      Ionosphere is that part of the thermosphere which extends above the mesosphere from 65 km to nearly 400 km above the earth’s surface. It is an electrically charged layer characterized by the ionization of atoms.

·      Due to the presence of electric charge in the Ionosphere, radio waves transmitted from the earth are reflected back to the earth by this layer.

·      Exosphere is the uppermost region of the atmosphere. It extends beyond the ionosphere above a height of about 400km. The air is extremely rarefied and the temperature gradually increases through the layer. Here the gravity of earth is exceedingly weak.

·      The lowest temperature of air is recorded just before sunrise, because of the predominance of land water in the north, the northern hemisphere is warmer

·      The pressure exerted by atmosphere as a result of its weight above a unit area of the earth’s surface is called the atmospheric pressure

·      Atmospheric pressure is expressed in millibars (mb) and is measured with a mercury barometer.

·      Two principal types of barometer used are mercury barometer and aneroid barometer

·      One millibar of atmospheric pressure is equal to the force of one gram on a square centimeter

·      The normal pressure at sea level is taken to be about 76 centimeters (1013.25 millibars)

·      Insolation is the radiant energy that reaches the surface of the earth from the sun. Insolation is the most important single source of atmospheric heat.

KERALA PSC / PHYSICAL GEOGRAPHY / STRUCTURE OF ATMOSPHERE / NOTES / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE