Mechanism of rain
- 1. 1 WARM WISHES BY-: KRITIKA MA’AM
- 2. RAINFALL DEFINATION FORMATION OF RAIN SIZE & INTENSITY OF RAIN TYPES OF RAINFALL MEASUREMENT OF RAINFALL MEASUREMENT OF FACTORS AFFECTING THE AMOUNT OF RAINFALL 2
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- 4. RAINFALL IS A FORM PRECIPITATION. IT OCCURS WHEN WATER VAPOUR IN THE ATMOSPHERE CONDENSE INTO DROPLETS THAT CAN NO LONGER BE SUSPENDED IN THE AIR. 4
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- 6. THIS PROCESS IS ALSO CALLED WATER CYCLE OR HYDROLOGICAL CYCLE 1. WATER IN THE WATER BODIES EVAPORATES DUE TO THE HEAT ENERGY PROVIDED BY SOLAR RADIATION. 2. THE WATER VAPOUR MOVES UPWARDS AND FORMS CLOUDS. 3. WHILE MUCH OF THE CLOUDS CONDENCE AND FALL BACK TO THE OCEANS AS RAIN, A PART OF THE CLOUDS IS DRIVEN TO THE LAND AREAS BY WINDS. 4. THERE THEY CONDENSE AND PRECIPATATE ONTO THE LAND MASS RAIN,SNOW,HAIL,DRIZZLE etc. 6
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- 9. SIZE OF RAINFALL MINIMUM SIZE OF RAINFALL IS 0.5 mm MAXIMUM SIZE OF RAINFALL IS ABOUT 6.0mm 9
- 10. INTENSITY OF RAINFALL TYPE INTENSITY LIGHT RAIN UP TO 2.5 mm/hr MODERATE RAIN 2.5 mm/hr to 7.5 mm/hr HEAVY RAIN >7.5 mm/hr VIOLENT RAIN >50 mm/hr 10
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- 12. THREE TYPES OF RAINFALL ARE 1.CONVECTIVE RAINFALL 2.OROGRAPHIC RAINFALL 3.FRONT OR CYCLONE RAINFALL 12
- 13. CONVECTIVE RAINFALL 13 A PACKET OF AIR WHICH IS WARMER THEN THE SURROUNDING DUE TO LOCALIZED HEATING RISES UPWARDS AND CONSEQUENTLY UNDER GO, COOLING,CONDENSTION AND PRECIPITATION.
- 14. OROGRAPHIC RAINFALL 14 THE MOIST AIR GET LIFTED UP TO HIGHER ALTITUDES DUE TO THE PRESENCES OF THE MOUNTAIN BARRIERS UNDER GO, COOLING,CONDENSTION AND PRECIPITATION.
- 15. FRONTIAL RAINFALL WHEN TWO AIR MASSES MEET THEY DO NOT MIX READILY DUE TO THE DIIFERENCES IN TEMPRATURE AND DENSITY. IN FRONT THERE IS LIKE AN IMAGINARY LINE SEPRATING TWO CONSTRASTING AIR MASSES. 15
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- 17. The rainfall is collected and measured in a rain gauge.Terms such as piiviometer , or barometer and iyeometer are also sometimes used to designate a rain gauge.For setting a rain gauge the following consideration are important: 1.The ground must be level and in the open and the instrument present a horizontal catch surface. 2.The gauge must be set as near the ground as possible to reduce2wind effects but it must be sufficiently high to prevent flood. 3.The instrument must be surrounded by an open fenced area of at least 5.5 mm X 5.5 m. 4.No object should be nearer to the instrument than 30 m or twice height of the obstruction. 17
- 18. Raingauge can be broadly classified into two categories- NON RECORDING GAUGES- Symon's Gauge RECORDING GAUGES- Tipping Bucket Type Weighing Bucket Type Natural Syphon Type 18
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- 20. FACTORS WHICH EFFECT THE AMOUNT OF RAINFALL ARE 1. LATITUDE 2.Temperature 3.Moisture Air 4.Masses Frontal 5.Activity Differential 6.Heating 7.Mountain Barrier 8.Distribution of Land & Water 20