The Indian Summer Monsoon:
Past, Present and Future
with special thanks to Andy Turner, Nick Klingaman and
Hilary Weller
Outline
• What the monsoon means for the people
of India
• Basic science of the monsoon
• History of the UK’s interest in ...
Some basic facts
• 1.13 billion people - one-sixth of the world's population -
live in a country one-third the size of the...
• ‘Monsoon’ means ‘season’, and describes a complete reversal of wind
regimes during the seasonal cycle. Monsoons are char...
Winds near the surface (925hPa)
Winter
Summer
Asian Monsoon
Indian Monsoon is part of a much larger circulation, the
Asian...
Pre-Monsoon Land/Sea Temperature contrasts
Nov./Dec.
May/June
Rainfall (mm/day)
Winter
Summer
Mountains and Monsoons
• Tibetan Plateau and the Asian Summer Monsoon
• East African Highlands and the Indian Summer Monso...
Mean Temperature in the Upper Troposphere (500 –
200mb)
Summer
Winter
Indian Monsoon Onset
Seasonal evolution of North-South gradient in
200-500hPa temperature
Climatological Onset Dates
Monsoon sweeps north and west
1 June
15 July
5 June
10 June
1 June
15 June
1 July
Snow-monsoon interactions
~2week delay to 
monsoon onset in 
heavy Himalayan 
snow case
Model Sensitivity Study: No Snow v...
East African Highlands, Somali Jet and
Indian Summer Monsoon
Impact of E. African Highlands on Asian Summer Monsoon
JJA: W/out Highlands JJA: With Highlands JJA: Impact of Highlands
J...
Long-Term Stability of the Indian Summer
Monsoon
UK’s fascination with the
meteorology of India
• India was Britain’s most important imperial and
economic possession. By t...
Henry Francis Blanford
1st British Director (Imperial Meteorological Reporter) of the
Indian Meteorological Department (18...
India holds the key to unraveling the laws of
the atmosphere!
Blanford argued that India offered a special situation for t...
From ‘The Indian Charivari’ – India’s equivalent of ‘Punch’: July 23, 1875
Long-Term Stability of the Indian Summer
Monsoon
"Disputed Empire“: Cartoon from Punch, 1877
Great Famine of 1877/78:
Conjunction of Politics and
Science
The Indian econom...
Sir Gilbert Thomas Walker
3rd British Director (Director General of Observatories) of the
Indian Meteorological Department...
El Nino, Southern
Oscillation and the
Walker Circulation
Decadal Variations in Indian Monsoon and El Nino
Seasonal mean
Interannual
Variability
ENSO-Monsoon
Teleconnections
Update...
Possible Players in Monsoon Variability
(+++ Level of confidence/knowledge)
• El Nino/Southern Oscillation (+++)
• Eurasia...
2001 2002
2003 2004 2005
Diversity of All-India
Daily Rainfall
What weather patterns
are linked to daily rainfall
variabil...
July 2002: Drought in India
Active-break cycles of the Indian Summer
Monsoon
Northward and eastward propagation associated
with the Madden Julian Osci...
MJO implicated in monsoon 2009
Major failure of monsoon rains: 23% below normal
Air-sea interaction and the MJO
Courtesy: Pete Inness
High Frequency Sea Surface Temperatures drive stronger
active-break cycles
Klingaman et al. (2008)
Lag correlations of intra-seasonally (30-50 day) filtered July and August rainfall
The importance of interactive upper-oce...
Mumbai flooding: July 26 2005
942 mm (37 inches) of rain in 24 hours
(A) Number (N) of heavy (R >
100 mm/day, bold line) and
moderate (5 < R < 100 mm/day,
thin line) daily rain events
(B) Num...
Indian Summer Monsoon is remarkably stable:
High societal vulnerability to small changes.
India is developing rapidly: Wil...
The Scientific Challenges
• How will the mean monsoon behave?
• How will climate change affect the stability of
the monsoo...
IPCC 4th Assessment Report: Projections of likely
shifts in rainfall patterns by 2080
% change in rainfall by end of 21st ...
Mean Annual Cycles of All-India
Rainfall and Temperature for end of 21st century
Current
A2: High
Emissions
B2: Low
Emissi...
Changes in rainfall during active and break phases
Break spellsActive spells
Current
2xCO2
Monsoon breaks may become more ...
Changing nature of
Indian rainfall with
climate change:
Impact of 2xCO2 on
number of rain days and
rainfall intensity
Chan...
Changes in the intensity of extreme Indian daily rainfall with
climate change
1 in 10 1 in 100 1 in 1,000 1 in 10,000
Curr...
Turner & Slingo 2010
But not all models agree with this simple
hypothesis…….
Impact of aerosols on the
monsoon
Pre-monsoon build up of absorbing aerosol from Arabian and
Saharan dust, Thar dust and local black carbon sources.
Aerosol...
Concluding Remarks
• Much still to learn about what controls the
monsoon and its variability
• Model improvements are vita...
Tropical Cyclone Gonu:
4 June 2007
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
The Indian summer monsoon:Past present and future_Julia Slingo_2010
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The Indian summer monsoon:Past present and future_Julia Slingo_2010

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This presentation on the Indian Summer Monsoon by Julia Slingo of Edinburgh Met Office (United Kingdom) broadly deals with what the monsoon means for the people of India and the basic science of monsoon.

The history of the United Kingdom’s interest in the Indian monsoon is discussed as also the challenges of climate change for India. Some basic facts regarding the Indian socio-economic context are presented to underline the importance of rainfed agriculture and hence the dependence on monsoons.

‘Monsoon’ means ‘season’, and describes a complete reversal of wind regimes during the seasonal cycle. Monsoons are characterised by a pronounced rainy season. Monsoons are driven by changes in the distribution of heating driven primarily by the seasonal cycle of the sun. A thermal contrast between land and sea is required to set up a monsoon. The Indian Monsoon is part of a much larger circulation, the Asian Monsoon.

The United Kingdom's fascination with the meteorology of India is presented. India appeared to offer an ideal natural laboratory for the science, and an ideal space in which to demonstrate the political importance of science in a global age. The British meteorologist Henry Francis Blanford had commented that "Order and regularity are as prominent characteristics of our (India’s) atmospheric phenomena, as are caprice and uncertainty those of their European counterparts."

From the political economy angle the British were of the view that the control of famine through climate prediction would mean that India could be governed more effectively. The presentation thereafter dealt with the changing nature of Indian rainfall and scientific challenges like:

How will the mean monsoon behave?
How will climate change affect the stability of the monsoon?
Will it become more variable?
Will it be less predictable?
What will climate change mean for extreme events?
How will changes in atmospheric composition affect the monsoon?

The IPCC’s 4th Assessment Report has projections of likely shifts in rainfall patterns by 2080. The changing nature of Indian rainfall with climate change is mainly due to the impact of 2xCO2 on the number of rain days and rainfall intensity. There will be a decrease in number of rain days and an increase in rain intensity on days when raining.

According to Slingo et al there will be changes in the intensity of extreme Indian daily rainfall with climate change. But not all models agree with this simple hypothesis. The impact of aerosols on the monsoons is highlighted viz., the pre-monsoon build up of absorbing aerosol from Arabian and Saharan dust, Thar dust and local black carbon sources.

The presentation finally concludes with the thought that there is much still to learn about what controls the monsoon and its variability. Model improvements are vital for making progress in monsoon prediction and impacts of climate change remain hugely uncertain for those reasons.

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The Indian summer monsoon:Past present and future_Julia Slingo_2010

  1. 1. The Indian Summer Monsoon: Past, Present and Future with special thanks to Andy Turner, Nick Klingaman and Hilary Weller
  2. 2. Outline • What the monsoon means for the people of India • Basic science of the monsoon • History of the UK’s interest in the Indian monsoon • Monsoon weather • Challenges of climate change for India
  3. 3. Some basic facts • 1.13 billion people - one-sixth of the world's population - live in a country one-third the size of the U.S. Over 37% live below the poverty line. • Population projected to rise to 1.8 billion by 2050. • World’s eleventh largest economy and second most rapidly growing economy with GDP growth rate last year of 6.7%. • Sustained by annual rainfall of around 1100mm, 80% of which arrives in the summer. • Agriculture accounts for nearly 20% of the GDP and employs over 50% of the total workforce. • 60% of agricultural production is rainfed and hence vulnerable.
  4. 4. • ‘Monsoon’ means ‘season’, and describes a complete reversal of wind regimes during the seasonal cycle. Monsoons are characterised by a pronounced rainy season. • Monsoons are driven by changes in the distribution of heating driven primarily by the seasonal cycle of the sun. A thermal contrast between land and sea is required to set up a monsoon. • In winter, the wind blows from the cold land over the warm sea. In summer, the warm land pulls in the wind from the ocean like a massive sea breeze. • Once established, the positive feedback between the circulation and latent heat release in the rain clouds maintains the monsoon What are Monsoons?
  5. 5. Winds near the surface (925hPa) Winter Summer Asian Monsoon Indian Monsoon is part of a much larger circulation, the Asian Monsoon
  6. 6. Pre-Monsoon Land/Sea Temperature contrasts Nov./Dec. May/June
  7. 7. Rainfall (mm/day) Winter Summer
  8. 8. Mountains and Monsoons • Tibetan Plateau and the Asian Summer Monsoon • East African Highlands and the Indian Summer Monsoon • Andes and the South American Monsoon • Sierra Madre and the North American Monsoon Topography (metres)
  9. 9. Mean Temperature in the Upper Troposphere (500 – 200mb) Summer Winter
  10. 10. Indian Monsoon Onset Seasonal evolution of North-South gradient in 200-500hPa temperature
  11. 11. Climatological Onset Dates Monsoon sweeps north and west 1 June 15 July 5 June 10 June 1 June 15 June 1 July
  12. 12. Snow-monsoon interactions ~2week delay to  monsoon onset in  heavy Himalayan  snow case Model Sensitivity Study: No Snow versus Heavy Snow No Snow Heavy Snow Turner & Slingo 2010
  13. 13. East African Highlands, Somali Jet and Indian Summer Monsoon
  14. 14. Impact of E. African Highlands on Asian Summer Monsoon JJA: W/out Highlands JJA: With Highlands JJA: Impact of Highlands JJA: W/out Highlands JJA: With Highlands JJA: Impact of Highlands 850 hPa winds Rainfall Slingo et al 2004
  15. 15. Long-Term Stability of the Indian Summer Monsoon
  16. 16. UK’s fascination with the meteorology of India • India was Britain’s most important imperial and economic possession. By the late 1860s India absorbed 1/5th of all British exports, so its economic importance was profound. • India appeared to offer an ideal natural laboratory for the science, and an ideal space in which to demonstrate the political importance of science in a global age. Reference: Predicting the Weather: Victorians and the Science of Meteorology by Katharine Anderson
  17. 17. Henry Francis Blanford 1st British Director (Imperial Meteorological Reporter) of the Indian Meteorological Department (1875-1889) ‘Order and regularity are as prominent characteristics of our (India’s) atmospheric phenomena, as are caprice and uncertainty those of their European counterparts.’
  18. 18. India holds the key to unraveling the laws of the atmosphere! Blanford argued that India offered a special situation for the study of meteorology: ‘We are in the position of a commander who can find no eminence from which he may gain a bird’s eye view of the combat. Could we but find some isolated tract of mountain, plain and ocean … girdled round by a giant mountain chain that should completely shut in and isolate some millions of square miles of the atmosphere, resting on a surface vast and varied enough to exhibit within itself all those contrasts of desert and forest, of plain, plateau and mountain ridge, of continent and sea, then the progress of meteorology would be assured.’
  19. 19. From ‘The Indian Charivari’ – India’s equivalent of ‘Punch’: July 23, 1875
  20. 20. Long-Term Stability of the Indian Summer Monsoon
  21. 21. "Disputed Empire“: Cartoon from Punch, 1877 Great Famine of 1877/78: Conjunction of Politics and Science The Indian economy was single- mindedly focused on its grain harvests. Indian taxes to administer the country and pay dividends to its investors depended entirely on the monsoon rains. Control of famine through climate prediction would mean that India could be governed more effectively.
  22. 22. Sir Gilbert Thomas Walker 3rd British Director (Director General of Observatories) of the Indian Meteorological Department (1904-1924) Pioneered statistical forecasting - formed a ’human computer’ with Indian staff performing a mass of statistical correlations using data from around the world ‘I think that the relationships of world weather are so complex that our only chance of explaining them is to accumulate the facts empirically.’ Introduced the terms Southern Oscillation, North Atlantic Oscillation, and North Pacific Oscillation
  23. 23. El Nino, Southern Oscillation and the Walker Circulation
  24. 24. Decadal Variations in Indian Monsoon and El Nino Seasonal mean Interannual Variability ENSO-Monsoon Teleconnections Updated from Slingo (1999)
  25. 25. Possible Players in Monsoon Variability (+++ Level of confidence/knowledge) • El Nino/Southern Oscillation (+++) • Eurasian and Himalayan snow amounts (+) • Indian Ocean sea surface temperatures and heat content (+) • Intra-seasonal variability e.g. active/break cycles (++)
  26. 26. 2001 2002 2003 2004 2005 Diversity of All-India Daily Rainfall What weather patterns are linked to daily rainfall variability? How predictable are they and on what lead times? How do they influence seasonal mean rainfall? What will happen under global warming?
  27. 27. July 2002: Drought in India
  28. 28. Active-break cycles of the Indian Summer Monsoon Northward and eastward propagation associated with the Madden Julian Oscillation (MJO) Courtesy; Peter Webster
  29. 29. MJO implicated in monsoon 2009 Major failure of monsoon rains: 23% below normal
  30. 30. Air-sea interaction and the MJO Courtesy: Pete Inness
  31. 31. High Frequency Sea Surface Temperatures drive stronger active-break cycles Klingaman et al. (2008)
  32. 32. Lag correlations of intra-seasonally (30-50 day) filtered July and August rainfall The importance of interactive upper-ocean thermodynamics for monsoon active-break cycles
  33. 33. Mumbai flooding: July 26 2005 942 mm (37 inches) of rain in 24 hours
  34. 34. (A) Number (N) of heavy (R > 100 mm/day, bold line) and moderate (5 < R < 100 mm/day, thin line) daily rain events (B) Number (N) of very heavy events (R > 150 mm/day) during the summer monsoon season over Central India. Changing nature of Indian rainfall (R) From Goswami et al. 2006, Science
  35. 35. Indian Summer Monsoon is remarkably stable: High societal vulnerability to small changes. India is developing rapidly: Will there be enough water to sustain that development? India and Climate Change
  36. 36. The Scientific Challenges • How will the mean monsoon behave? • How will climate change affect the stability of the monsoon? – Will it become more variable? – Will it be less predictable? • What will climate change mean for extreme events? • How will changes in atmospheric composition affect the monsoon?
  37. 37. IPCC 4th Assessment Report: Projections of likely shifts in rainfall patterns by 2080 % change in rainfall by end of 21st century, where more than 2/3 of the models agree on the sign of the change.
  38. 38. Mean Annual Cycles of All-India Rainfall and Temperature for end of 21st century Current A2: High Emissions B2: Low Emissions
  39. 39. Changes in rainfall during active and break phases Break spellsActive spells Current 2xCO2 Monsoon breaks may become more severe – impacts on agriculture
  40. 40. Changing nature of Indian rainfall with climate change: Impact of 2xCO2 on number of rain days and rainfall intensity Change in number of wet days Change in rainfall intensity • Decrease in number of rain days • Increase in rain intensity on days when raining From: Turner & Slingo 2008
  41. 41. Changes in the intensity of extreme Indian daily rainfall with climate change 1 in 10 1 in 100 1 in 1,000 1 in 10,000 Current 2xCO2 From: Turner & Slingo 2008 X X – Expected Increase from Clausius Clapeyron
  42. 42. Turner & Slingo 2010 But not all models agree with this simple hypothesis…….
  43. 43. Impact of aerosols on the monsoon
  44. 44. Pre-monsoon build up of absorbing aerosol from Arabian and Saharan dust, Thar dust and local black carbon sources. Aerosol is not all washed out during monsoon: gaps in rainfall allow burden to build up. Lau et al., GEWEX News 18, #1
  45. 45. Concluding Remarks • Much still to learn about what controls the monsoon and its variability • Model improvements are vital for making progress in monsoon prediction • Impacts of climate change remain hugely uncertain for those reasons • 2010: Normal (98%) predicted by Indian Meteorological Department
  46. 46. Tropical Cyclone Gonu: 4 June 2007
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