Monsoon and drought


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This document explains about climatic conditions based on monsoon rains

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Monsoon and drought

  1. 1. A presentation by:Apoorva Sancheti
  2. 2. Introduction• “Water is life” a famous quote.• Many suktas to be found in the Vedas and Upanishads about water.• The first traces of human civilization and settlements were witnessed by rivers.• Water has played an important role in the development of human race.• Water in science is H2O
  3. 3. Rains• Various sources of water.• the purest and important source is rain.• Rain is a blessing that connects heaven and earth.• The water cycle is one of the most important cycles of nature.
  4. 4. The hydraulic cycle• The water cycle is the way the Earth uses and recycles water. Its controlled by the sun, which produces energy in the form of heat. This heat energy causes the water in the worlds oceans, lakes, and even puddles in your backyard to warm and evaporate.• When water is heated, it changes from a liquid to a gas. This gas is called water vapor, and the process is called evaporation. When plants give off water vapor, its called transpiration.
  5. 5. • When water evaporates, it rises into the cooler air, collects, and forms clouds. There, the water vapor molecules cool down and change back into liquid water. This is called condensation.• As more and more water vapor cools into the clouds, the water droplets that form the clouds become larger and larger. These droplets get so big that the swirling winds in the atmosphere can no longer hold them up. The droplets fall from the sky.• Precipitation is the term for the falling, condensed water molecules, which come down as rain, snow, sleet, or hail--depending on conditions in the atmosphere. ..
  6. 6. 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.
  7. 7. Monsoon• Comes from an Arabic word “mausim”. Means season.• The ancient traders traveling in the Indian ocean and Arabian sea used this term to describe the system of alternating winds which blew from northeast during winter and southwest during summer.
  8. 8. Definition• Monsoons are seasonal rains that drench the countryside with water.• They are annually recurring weather phenomenon.
  9. 9. Reasons for monsoon• Due to land and sea temperature differences.• land reflects the sun’s rays heating air over land more rapidly. The specific heating capacity of components of earth is much more than water.• water is able to absorb a lot of heat without itself changing temperature much. So air over water remains relatively cooler. This creates high and low pressure areas.
  10. 10. Differential heating phenomenon
  11. 11. • the air over high pressure areas migrate to low pressure areas. As the heated air in low pressure area rises up, the air from high pressure areas takes its place.• The winds that blow from sea to land carry humidity and as they move towards low pressure areas i.e. land, they rise up due to mountains, surface heating, convergence at the land. Thus the air cools due to expansion in lower pressure causing condensation.
  12. 12. • This cycle continues as cooling air creates precipitation and releases energy. this energy heats the air which rises and flows back to the sea. cools and rushes back to the land to replace more warm air.• This phenomenon is observed in Asia as the northern hemisphere has much more land mass than southern hemisphere.• during summer the earth is tilted at such an angle that the sun’s rays shine more directly on the northern hemisphere heating the land mass.• thus it is a cyclical process.
  13. 13. Seasonal wind currents
  14. 14. Types of monsoon.• In the Indian subcontinent 2 types are observed.
  15. 15. 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.
  16. 16. • Northeast or winter monsoon.• occurs during winter. the sea water holds heat whereas the land cools off immediately. Thus low pressure is created over the ocean. Cold winds blow from the land to the sea collecting moisture from tropical waters as they travel and release it over Indonesia,Srilanka, Indian east coast.• from December to early march.• Also known as the retreating monsoon.
  17. 17. History• Asian monsoon is linked to the upliftment of Tibetan plateau after the collision of India and Asia around 50 million years ago.• monsoon first became strong around 8 million years ago. Based on records from the Arabian sea and the records of wind blown to the loess plateau of china.• varied significantly in strength since then. linked largely to global climate change.• Strengthening of Indian monsoon happened around 5 million years ago due to an interval of closing of Indonesian seaway. This increased sea surface temperature.
  18. 18. • Thus today monsoon is an important feature of the Indian sub continent.• it is the biggest support to the agriculture here and even other related industries.• Along with the Indian subcontinent, and other parts of Asia monsoons also occur in north America, Africa, south America.
  19. 19. Measurement• Rain is generally measured in millimeter i.e. mm. this shows the quantity of rainfall over a particular area. It can also be converted to cm. or meters. » simple rain gauge -
  20. 20. Meteorological dept.• This department deals with the temperature, weather of an area. It predicts the weather and thus gives alert signals in case a natural calamity predicted to occur.• gives us the daily report of how much rainfall occurred in which area and also what will be the situation in the next 48 hours. It also predicts when monsoons will hit which region and so on.
  21. 21. Satellite images• provides us with the satellite images which enable us to know where the clouds are heading and regions which will get heavy rainfall.
  22. 22. Monsoons in India
  23. 23. Droughts• When there is not enough rain to support people or crops.• It may rain but scanty rainfall.
  24. 24. Causes of droughts• If no low pressure area is created then the air currents and clouds are pushed downwards .• High pressure systems can be stalled by jet streams, wide bands of fast moving air. in the upper atmosphere.• unusual currents of cold and warm water in the ocean.• Water vapor not brought by air currents to the right area at the right time. if winds are not strong.
  25. 25. Global wind currents
  26. 26. Causes of droughts• Mountains can prevent winds from blowing moisture to the needed areas. Such areas are also known as rain shadow areas and are generally drought prone. As the air rises above a mountain it becomes cooler and condenses. Thus deserts are found on a side of a mountain facing away from the sea.
  27. 27. Prediction• Can know when occurred in the past by the tree rings. wide rings show good growth and thin rings means stunted growth.• generally occur in the cycle of 22 years.• Predicted that such patterns are caused by sun spots i.e. dark cool areas on the surface of the sun.
  28. 28. • These may cause slightvariations in air temperatureenough to cause a drought.• But still not proved.
  29. 29. Preparation• Need to limit the use of water by each individual.• If situation is very serious then need for rationing of water
  30. 30. Year 2008 • At this time it was predicted that like the 2 previous years this year too there will be good rainfall. • the conditions were favorable. low pressure• This year the monsoons area created on the west arrived on time much to coast. Cyclones were everyones surprise. predicted in the bay of• Hit the coast of kerela on Bengal. 25th may and reached • the north east region was maharashtra by 10th June. under low pressure areas.
  31. 31. Onset and retreat of monsoon in India
  32. 32. Clouds over mumbai
  33. 33. • In maharashtra it rained for a week or so. Not too heavily though. then it stopped raining on around 15 June.• The next predictions made were all very positive. Low pressure areas had developed in the bay of Bengal and also the central India.• the satellite images showed clouds aligned on the western coast. Headlines said 22nd June.• But days past by without the trace of rain. Farmers had not sowed seeds. Others had but they did not grow well as there was no rain.• 2nd July and pune had got around 19.9mm rainfall• Meteorological dept. declared that the speed of the winds this year was thrice than what it was
  34. 34. last year at the same time. last year the speed was 4 to 12km per hr. whereas this year it was14 to 21km per hr.• This led to decrease in air humidity. It was 52 to 68 in comparison to 70 to 90.• The rate of evaporation from soil was more than 14 to16mm compared to 3 to4 mm last year.• Due to the strong winds, monsoon did not stabilize in maharashtra.• They were blown towards Bengal, orissa,U.P., and the northeast• Drought was declared in the state on 10th July.• People seen performing poojas and sacrifices to rain god.
  35. 35. Wind speed
  36. 36. • The rains did not even reach 15% of the average of last year’s rain during this time.• Pune expected an average of 600 to 800 mm.• Discussions about “prakalp varsha”. But no decisions taken. it was declared to be too late. this project was to create artificial rainfall by spraying silver iodide on the gathered clouds with the help of airplane. this makes the cloud heavy and it bursts and precipitates.• In the first week of august it started raining again and on 5th august vidarbha and konkan flooded due to too much rain.• Pune received around 6 mm rainfall in two days from 3rd to 5th.on 8th it was 32mm.
  37. 37. Calculation of rainfall.• Let us calculate the amount of water we receive here in vigyan ashram.• The average rainfall here is around 550mm.[ the calculated from the rainfall of last 10years.]• The area in consideration is 5 acres. that compromises of the ashram area. as per the calculations, 1 acre=40 guntha. Thus the total land is 200 gunthas.• The area of one guntha is 10m *10m.
  38. 38. • The total area is thus 200* 100= 20000m2.• The total requirement of the ashram if we consider 50lt per person per day = 2000lt.• since we have around 10 animals who need about 60lt per day per animal = 600lt. Therefore the total amount is 2600lt Per day.• Thus the whole year’s requirement is 9,49,000 lit/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.
  39. 39. • If we save even 10% of this it means we get 11,00,000 lit which is 1,51,000 lt. more than what we need.• Taking the lowest rainfall i.e. 250mm we still get 50,00,000 lt and 10% of this means 5,00,000 lt.
  40. 40. • So is it that nature provides us with less rain or is it that we do not value the gift?• it is time to ask our selves and stop blaming nature.• Droughts may not always be natural calamities but in fact are many times political.• what we can do is harvest every drop of water …….