CLASS 9TH AIR CHAPTER GEOGRAPHY CH 4 NOTE

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1. CHAPTER-04 AIR GEOGRAPHY

2. KEYWORDS ATMOSPHERE: Huge blanket of air around the earth. GLOBAL WARMING: Rise in temperature on the earth due to factory smoke, car fumes etc. INSOLATION: Incoming solar energy intercepted by the earth. It decreases from equator towards the poles. TEMPERATURE : The degree of hotness and coldness of the air. WEATHER : Day to day change in the condition of atmosphere. CLIMATE : Average weather conditions of a place for a longer period of time. AIR PRESSURE : Pressure exerted by the weight of air on the earth’s surface. Highest – Sea level Decreases – With height NOTE : Air always moves from high pressure to low pressure

3. KEYWORDS WIND : The movement of air from high pressure area to low pressure area is called wind. CYCLONE: A storm or system of winds that rotates around a center of ow atmospheric pressure at a speed of 20-30 miles/hour HUMIDITY: Moister/water content present in air. PRECIPITATION: Falling of water on earth in the form of rainfall. BAROMETER: An instrument that measures atmospheric pressure. RAINGAUGE : An instrument for measuring the amount of rainfall. ISOBAR : An imaginary line drawn on a weather map joining all the places having same air pressure.

4. EXPLANATION OF CHAPTER ATMOSPHERE The blanket of air around the earth Protects us from harmful rays of sun Nitrogen -- 78 ٪ Oxygen -- 21 ٪ Other -- 01 ٪

5. EXPLANATION OF CHAPTER COMPOSITION OF ATMOSPHERE Nitrogen -- 78 ٪ (Bulk in atmosphere) Oxygen -- 21 ٪ Other -- 01 ٪ Nitrogen – Important for plants Oxygen – Important for human and animals CO2 – Important for plants

6. EXPLANATION OF CHAPTER STRUCTURE OF ATMOSPHERE :- (5 Layers) EXOSPHERE (5 th Layer) THERMOSPHERE (4 th Layer) MESOSPHERE (3 rd Layer) STRATOSPHERE (2nd Layer) TROPOSPHERE (1st Layer)

7. LAYERS OF ATMOSPHERE TROPOSPHERE: Present oxygen we breath All weather related phenomena occurs here like rain, fog etc. 13 Km Height STRATOSPHERE: 50 km Aeroplanes fly Contains a layer of Ozone Gas

8. LAYERS OF ATMOSPHERE MESOSPHERE: 80 Km. Meteorites burn up here while entering from space THERMOSPHERE: 80-400 km Temperature increases with height Ionosphere Helps in radio transmission

9. LAYERS OF ATMOSPHERE EXOSPHERE: Uppermost layer Very thin layer Light gases like helium and hydrogen float into the space from this layer WEATHER: Day to day change in the condition of atmosphere. CLIMATE: Average weather conditions of a place for a longer period of time.

10. TEMPERATURE : The degree of hotness and coldness of the air. Measured in degree Celsius (Unit) INSOLATION : Incoming solar energy intercepted by the earth. It decreases from equator towards the poles.

11. AIR PRESSURE : Pressure exerted by the weight of air on the earth’s surface. Go up – Falls/Decreases Sea Level – Highest High Temperature – Low pressure Low Temperature – High pressure In high pressure –Clear and sunny sky In low pressure – Cloudy and wet Air moves – High to low pressure area

12. WIND : The movement of air from high pressure area to low pressure area is called wind. Divided into 3 types:- Permanent Winds (Ex-Westerlies & Easterlies) Seasonal Winds (Monsoon) Local Winds (Loo and Land & Sea breeze) MOISTURE : It is also called Humidity which is present in air. Clouds are masses of water droplets formed by condensation of water vapour . Then clouds leave these water droplets in the form of precipitation ( Ex- Rain, Snow, Hail etc.)