Monsun & drought

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This PPT slide gives information on monsoon and drought climatic conditions

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Monsun & drought

  1. 1. Introduction• “Water is life” a famous quote.• Many suktas to be found in the Vedasand Upanishads about water.• The first traces of human civilization andsettlements were witnessed by rivers.• Water has played an important role in thedevelopment of human race.• Water in science is H2O
  2. 2. Rains• Various sources of water.• the purest and important source is rain.• Rain is a blessing that connects heavenand earth.• The water cycle is one of the mostimportant cycles of nature.
  3. 3. The hydraulic cycle• The water cycle is the way the Earth uses and recycleswater. Its controlled by the sun, which producesenergy in the form of heat. This heat energy causesthe water in the worlds oceans, lakes, and evenpuddles in your backyard to warm and evaporate.• When water is heated, it changes from a liquid to agas. This gas is called water vapor, and the process iscalled evaporation. When plants give off water vapor,its called transpiration.
  4. 4. • When water evaporates, it rises into the coolerair, collects, and forms clouds. There, the watervapor molecules cool down and change backinto liquid water. This is called condensation.• As more and more water vapor cools into theclouds, the water droplets that form the cloudsbecome larger and larger. These droplets get sobig that the swirling winds in the atmosphere canno longer hold them up. The droplets fall fromthe sky.• Precipitation is the term for the falling,condensed water molecules, which come downas rain, snow, sleet, or hail--depending onconditions in the atmosphere...
  5. 5. When water falls to the Earth, the water seeps into the soilbecause of the force of gravity. This seeping is calledinfiltration. Or the water flows over the land and into bodies ofwater, such as rivers and lakes. Sometimes this watercollects nutrients from the soil it runs over, making the valleygood for plant growth.
  6. 6. Monsoon• Comes from an Arabic word “mausim”.Means season.• The ancient traders traveling in the Indianocean and Arabian sea used this term todescribe the system of alternating windswhich blew from northeast during winterand southwest during summer.
  7. 7. Definition• Monsoons are seasonal rains thatdrench the countryside with water.• They are annually recurring weatherphenomenon.
  8. 8. Reasons for monsoon• Due to land and sea temperature differences.• land reflects the sun’s rays heating air overland more rapidly. The specific heating capacityof components of earth is much more thanwater.• water is able to absorb a lot of heat withoutitself changing temperature much. So air overwater remains relatively cooler. This createshigh and low pressure areas.
  9. 9. Differential heating phenomenon
  10. 10. • the air over high pressure areas migrateto low pressure areas. As the heated air inlow pressure area rises up, the air fromhigh pressure areas takes its place.• The winds that blow from sea to land carryhumidity and as they move towards lowpressure areas i.e. land, they rise up dueto mountains, surface heating,convergence at the land. Thus the aircools due to expansion in lower pressurecausing condensation.
  11. 11. • This cycle continues as cooling air createsprecipitation and releases energy. this energyheats the air which rises and flows back to thesea. cools and rushes back to the land toreplace more warm air.• This phenomenon is observed in Asia as thenorthern hemisphere has much more landmass than southern hemisphere.• during summer the earth is tilted at such anangle that the sun’s rays shine more directly onthe northern hemisphere heating the landmass.• thus it is a cyclical process.
  12. 12. Seasonal wind currents
  13. 13. Types of monsoon.• In the Indian subcontinent 2 types areobserved.
  14. 14. Southwest or summer monsoon.• Occurs during summer. in the northernhemisphere low pressure area is created.winds from southern hemisphere blow northto replace the hot winds. These carrymoisture. thus winds blow from Indian oceantowards central India.• From June to September.
  15. 15. • Northeast or winter monsoon.• occurs during winter. the sea water holdsheat whereas the land cools offimmediately. Thus low pressure is createdover the ocean. Cold winds blow from theland to the sea collecting moisture fromtropical waters as they travel and releaseit over Indonesia,Srilanka, Indian eastcoast.• from December to early march.• Also known as the retreating monsoon.
  16. 16. History• Asian monsoon is linked to the upliftment ofTibetan plateau after the collision of India andAsia around 50 million years ago.• monsoon first became strong around 8 millionyears ago. Based on records from the Arabiansea and the records of wind blown to the loessplateau of china.• varied significantly in strength since then. linkedlargely to global climate change.• Strengthening of Indian monsoon happenedaround 5 million years ago due to an interval ofclosing of Indonesian seaway. This increasedsea surface temperature.
  17. 17. • Thus today monsoon is an importantfeature of the Indian sub continent.• it is the biggest support to the agriculturehere and even other related industries.• Along with the Indian subcontinent, andother parts of Asia monsoons also occurin north America, Africa, south America.
  18. 18. Measurement• Rain is generallymeasured in millimeteri.e. mm. this shows thequantity of rainfall overa particular area. It canalso be converted tocm. or meters.» simple rain gauge -
  19. 19. Meteorological dept.• This department deals with thetemperature, weather of an area. Itpredicts the weather and thus gives alertsignals in case a natural calamitypredicted to occur.• gives us the daily report of how muchrainfall occurred in which area and alsowhat will be the situation in the next 48hours. It also predicts when monsoons willhit which region and so on.
  20. 20. Satellite images• provides us withthe satellite imageswhich enable us toknow where theclouds are headingand regions whichwill get heavyrainfall.
  21. 21. Monsoons in India
  22. 22. Droughts• When there is not enough rain to supportpeople or crops.• It may rain but scanty rainfall.
  23. 23. Causes of droughts• If no low pressure area is created then theair currents and clouds are pusheddownwards .• High pressure systems can be stalled byjet streams, wide bands of fast moving air.in the upper atmosphere.• unusual currents of cold and warm waterin the ocean.• Water vapor not brought by air currents tothe right area at the right time. if winds arenot strong.
  24. 24. Global wind currents
  25. 25. Causes of droughts• Mountains can prevent winds from blowingmoisture to the needed areas. Such areasare also known as rain shadow areas andare generally drought prone. As the airrises above a mountain it becomes coolerand condenses. Thus deserts are foundon a side of a mountain facing away fromthe sea.
  26. 26. Prediction• Can know when occurred in the past by thetree rings. wide rings show good growth andthin rings means stunted growth.• generally occur in the cycle of 22 years.• Predicted that such patterns are caused bysun spots i.e. dark cool areas on the surfaceof the sun.
  27. 27. • These may cause slightvariations in air temperatureenough to cause a drought.• But still not proved.
  28. 28. Preparation• Need to limit the useof water by eachindividual.• If situation is veryserious then need forrationing of water
  29. 29. Year 2008• This year the monsoonsarrived on time much toeveryones surprise.• Hit the coast of kerela on25thmay and reachedmaharashtra by 10thJune.• At this time it was predictedthat like the 2 previousyears this year too therewill be good rainfall.• the conditions werefavorable. low pressurearea created on the westcoast. Cyclones werepredicted in the bay ofBengal.• the north east region wasunder low pressure areas.
  30. 30. Onset and retreat of monsoon inIndia
  31. 31. Clouds over mumbai
  32. 32. • In maharashtra it rained for a week or so. Nottoo heavily though. then it stopped raining onaround 15 June.• The next predictions made were all very positive.Low pressure areas had developed in the bay ofBengal and also the central India.• the satellite images showed clouds aligned onthe western coast. Headlines said 22ndJune.• But days past by without the trace of rain.Farmers had not sowed seeds. Others had butthey did not grow well as there was no rain.• 2ndJuly and pune had got around 19.9mm rainfall• Meteorological dept. declared that the speed ofthe winds this year was thrice than what it was
  33. 33. last year at the same time. last year the speedwas 4 to 12km per hr. whereas this year it was14to 21km per hr.• This led to decrease in air humidity. It was 52 to68 in comparison to 70 to 90.• The rate of evaporation from soil was more than14 to16mm compared to 3 to4 mm last year.• Due to the strong winds, monsoon did notstabilize in maharashtra.• They were blown towards Bengal, orissa,U.P.,and the northeast• Drought was declared in the state on 10thJuly.• People seen performing poojas and sacrifices torain god.
  34. 34. Wind speed
  35. 35. • The rains did not even reach 15% of the averageof last year’s rain during this time.• Pune expected an average of 600 to 800 mm.• Discussions about “prakalp varsha”. But nodecisions taken. it was declared to be too late.this project was to create artificial rainfall byspraying silver iodide on the gathered cloudswith the help of airplane. this makes the cloudheavy and it bursts and precipitates.• In the first week of august it started raining againand on 5thaugust vidarbha and konkan floodeddue to too much rain.• Pune received around 6 mm rainfall in two daysfrom 3rd to 5th.on 8thit was 32mm.
  36. 36. Calculation of rainfall.• Let us calculate the amount of water we receivehere in vigyan ashram.• The average rainfall here is around 550mm.[ thecalculated from the rainfall of last 10years.]• The area in consideration is 5 acres. thatcompromises of the ashram area. as per thecalculations, 1 acre=40 guntha. Thus the totalland is 200 gunthas.• The area of one guntha is 10m *10m.
  37. 37. • The total area is thus 200* 100= 20000m2.• The total requirement of the ashram if weconsider 50lt per person per day = 2000lt.• since we have around 10 animals who needabout 60lt per day per animal = 600lt.Therefore the total amount is 2600lt Per day.• Thus the whole year’s requirement is 9,49,000lit/year.• The average rainfall is 550mm = 0.55m.• Thus the total rainfall over this land = area*ht.• =20000*0.55 = 11,000m3.• One meter3 = 1000lt.• Thus total amount in liters = 1,10,00,000 lt.
  38. 38. • If we save even 10% of this it means weget 11,00,000 lit which is 1,51,000 lt.more than what we need.• Taking the lowest rainfall i.e. 250mm westill get 50,00,000 lt and 10% of thismeans 5,00,000 lt.
  39. 39. • So is it that nature provides us with lessrain or is it that we do not value the gift?• it is time to ask our selves and stopblaming nature.• Droughts may not always be naturalcalamities but in fact are many timespolitical.• what we can do is harvest every drop ofwater …….

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