I. Fill in the blanks with suitable words:
1.The two major gases of the atmosphere are ______ and _________
2.The lowest layer of the atmosphere is ________
3.The average air pressure of the atmosphere at the sea level is ___________
4.Westerlies is also known as ___________
5.The scientific study of weather is ___________
Ans: (I) nitrogen, oxygen (2) Troposphere (3) 1013.25mb
(4) Trade winds (5) Meteorology.
II. Answer the following questions:
1. What is atmosphere?
Ans: Atmosphere is a thin layer of gases, dust particles and water vapour surrounding the earth. This layer of gases forms protective boundary between the outer space and the earth's surface.
2.Name the important layers of the atmosphere.
Ans: (a) Troposphere, (b) Stratosphere, (c) Mesosphere,
(d) Thermosphere (e) Exosphere.
3.What is the significance of ozone layer?
Ans: Ozone layer absorbs ‘ultraviolet rays’ of the sun and protects all forms of life on the earth.
4. What is Doldrums? Where is it found?
Ans: The Equatorial low pressure belt is called Doldrums. This region gets direct rays of the Sun almost throughout the year. This is a calm region with very little wind so it is called Doldrums. Doldrums means belt of calmness. This region lies between 0° to 5° North and South of the equator.
5.Name the different types of planetary winds.
Ans: There are three types of planetary winds. They are-
(a) Trade winds, (b) Anti-trade winds and (c) Polar winds.
6.What are local winds? Give any two examples.
Ans: Periodic winds are the result of variation in local temperature, pressure, humidity which in turn are attributed to the formation of air currents, crossing mountain ranges, valleys and other relief barriers. The important periodic and local winds are Land breeze, Sea breeze, Mountain breeze, valley breeze, etc.
7. Mention the different types of clouds.
Ans: The different types of clouds are- the Stratus, the Cumulus, the Cirrus and the Nimbus clouds.
8.Distinguish between weather and climate.
Ans: Weather: The atmospheric condition of a smaller area at a particular time is called weather. For example cloudy, sunny, fine weather, etc.
Climate: Climate is the average condition of the atmosphere over a long period of time of a larger area. Example- Equatorial climate, Tropical climate, etc.
III. Define the following:
1.Ionosphere: Thermosphere is called Ionosphere as the gaseous atoms are ionized due to very high temperature. The ions found in this layer help in reflecting radio waves.
2.Normal lapse rate: It is the decreasing rate of temperature with the increase of altitude. The rate of decrease is 1° C for every 165 meters or 6.4° for every 1000 meters of height.
3.Torrid Zone: Torrid Zone is the zone of high temperature. This region is found between O° or equator and Tropic of Cancer (23½° N) in the north and the Equator and Tropic of Capricorn (23½° S) in the south. This region receives direct rays of the sun.
4.Horse latitudes: Sub-tropical high pressure belts that lie between 30° and 35° north and south of the equator are high pressure belts. The North sub-tropical high pressure belt that lies between 30° and 35° north are also called 'Horse latitude'.
5.Orographic rainfall: Orographic rainfall is also called 'Mountain rainfall' or 'Relief rainfall'. When moisture laden air is obstructed by a mountain barrier, the air is forced to rise up. As the air rises upwards, it cools and gets saturated. Further cooling of this air causes condensation resulting in orographic rainfall.
6.Climatology: The scientific study of climate is called