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fast and at night, it cools very fast. On the other         Quiz Time
            hand, the heating process of sea water is very
            slow. This results the cool breeze from the sea          Answer the questions :
            during the day. In the night, the land is cooler, so     1. What is the importance of oxygen?
            a cool breeze blows into the sea. These winds            2. Where do all the weather phenomena occur in
            help to reduce the difference in the day and night          the atmosphere?
            temperatures of areas near the shoreline and there
            is not much difference between summer and                3. In which layer of the atmosphere the aeroplanes
            winter temperatures.                                        fly?
                                                                     4. Name two major elements of weather and
            Altitude
                                                                        climate.
            As given earlier, the higher you go above the
            ground level, the cooler it is. Temperature              5. At which point of the earth, the effect of
            decreases by about 1°C for every 100 m increase             insolation is very less?
            in altitude.                                             6. What are the freezing and boiling points on the
                                                                        Fahrenheit scale?
                 Info Bits
                 Info Bits                                           Atmospheric Air Pressure

                                                                    The weight of air pushing down on a unit area on
            The temperature of air decreases with increasing
            height at the rate of 1°C for every 165 m. This is      the earth’s surface is called atmospheric pressure .
            called the normal lapse rate.                           It is measured by the instrument called barometer
                                                                    and the unit in which it is measured is milibar    .
            Surface Type                                            The normal atmospheric pressure at sea level is

            The surface of a town or a city with lots of            about 76 cm of the mercury column in the
            concrete structures, will absorb more of insolation     barometer.       Polar HP
            than a forest or the moist soil surface of a village.                                Polar Easterlies
            So temperatures in cities or towns are greater than                     Sub-polar LP       60°N-65°N
            in rural areas. Similarly, the barren surface of the                                     South-Westerly Winds
                                                                                    Sub-tropical HP      30°N-35ºN
            desert heats up quickly.
                                                                                                       North-East Trade Winds
            Measurement of Temperature :        Temperature is                                         0°
            measured     by    an    instrument    called   the                                        South-East Trade Winds
            thermometer.    It   measures    the   atmospheric                      Sub-tropical HP      30°S-35°S
            temperature on a Fahrenheit or a Celsius scale.                                          North-Westerly Winds
                                                                                    Sub-polar LP   60°S-65°S
            On the Fahrenheit scale, the freezing point is
                                                                                                 Polar Easterlies
            32°F and the boiling point is 212°F. On the                              Polar HP
            Celsius scale, the freezing point is 0°C and the                            Pressure Belts
            boiling point is 100°C. We can convert the              Factors Affecting Atmospheric Pressure
            Fahrenheit reading into celsius reading or vice         Temperature   and altitude  are two factors which
            versa using the following formulae :
                                                                    influence atmospheric pressure. Air expands on
               °F = °C ×   + 329 9     °C = (°F – 32) × 5           being heated and becomes light. This hot air then
                            5                             9         rises upwards, creating areas of low pressure. Low
                                                                    pressure is associated with cloudy sky and wet
                 Info Bits
                 Info Bits                                          weather. In contrast, the cold air contracts, and
                                                                    becomes heavy and settles down creating an area
            The Fahrenheit scale was invented by Daniel             of high pressure. High pressure is associated with
            Fahrenheit and the Celsius scale was invented by        clear and sunny sky. Atmospheric pressure is also
            Andres Celsius. In India, Celsius scale is generally    affected by the rotation of the earth.
            used.
                                                                                                The Atmosphere
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