2. • What is monsoon?
• Where can we see monsoons?
• Why are monsoons important?
• What is the physical mechanism of
monsoon?
• Examples: Asian monsoon, North
American monsoon, West African
monsoon
• Can we predict monsoons?
3. What is monsoon?
‘A name for a wind system that
changes in speed and direction
with season.’ (derived from an Arab
word)
7. Cold season: Dry winds blow from land to
ocean
Warm season: Wet winds blow from ocean to
land
transport moisture
large rainfall
8. Why are monsoon rainfalls important?
water management, disaster mitigation, agricultural
efficiency
e.g.) Asian monsoons
About 60% of the world’s population depends on
monsoon
e.g.) Asian monsoons (India)
•8.2 % economic growth in the year
ending 2004 March with the help of the
good monsoon
•5.5-6.5% in this year’s growth because
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summer. (Asian Development Bank)
•Onset, extent and overall amount of
monsoon rainfall play a key role
11. Mechanisms of monsoon
Temperatures over oceans do not change as much as over lands
January Surface Air Temperature
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12. July Surface Air Temperature
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13. Large differences occur over the continents and smaller
ones over the oceans- an indication of the heat capacity
of the surface
Difference between the
January and July surface
temperature
14. Mechanisms of monsoon
July SLP
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15. Mechanisms of monsoon
January SLP
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19. July
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SLP
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Wind
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Surface Wind: January
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SLP
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Wind
21. ~ Gigantic land-sea breeze ~
Warm season
L H
cold warm
H L
wet
Ocean Land
Chen et al. 2002
22. Cold season
H L
warm cold
L H
dry
Ocean Land
Chen et al. 2002
23. Examples of monsoons
1. Asian monsoon : the largest monsoon
India, Sri Lanka, Bangladesh, Indonesia and etc
SW monsoon
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NE
From:http://snrs.unl.edu/amet
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monsoon
351/ogren/monsoons.html
24. The Current system of the Indian Ocean
From:Tomczak, Matthias & J Stuart Godfrey: Regional Oceanography:
25. History of Indian summer monsoon rainfall
prediction From:http://www.met.rdg.ac.uk/cag/MOL/Introduction/frameinde
x.html
Motivated by the Great Indian Drought of
1877, the India Meteorological Department is
established in 1875 for the seasonal forecast
of Indian monsoon rainfall.
In the early part of the 20th century, Sir
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Gilbert Walker studied the global
teleconnections of monsoon for the monsoon
rainfall prediction, which led him to the
discovery of Southern Oscillation.
.
26. The factors influencing interannual
variability Indian summer monsoon
rainfall
• Himalayan snow cover
more snow ⇒higher albedo
⇒ less ∆T
⇒ weaker monsoon
• Soil moisture
more moisture ⇒ less ∆T
⇒ weaker monsoon
• ENSO
• ?
• ?
27. 2. North American monsoon
~ Southwest United States monsoon
~ Mexican monsoon
~ Arizona monsoon
Increase in rainfall during summer over the dry regions
about 35% of Arizona's annual precipitation
about 45% of New Mexico's annual precipitation,
about 60% of northern Mexico’s annual precipitation
29. Mid-to late summer rainfall
Seasonal distribution of precipitation
across southwestern
max following extremely dry
North America. Note that northwestern condition
Mexico shows the
strongest monsoon signal, which
diminishes through Arizona,
New Mexico, and Nevada. Northeastern
Mexico and Texas
display early summer–late fall
precipitation peaks, while the West
Coast has a dry summer Mediterranean
distribution (vertical axis
of all graphs represents 180 mm with 20
mm increments). Areas
south of the broken line receive greater
than 50% of their annual
rainfall in July, August, and September
(after Douglas et al. 1993).
31. Predictability
Monsoon rainfall :
Important water resources QuickTime™ and a
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Hazards(storms)
Monsoon influenced
thunderstorm
USA today 06/25/2004
The North American Monsoon Experiment, announced
Friday, is getting underway this month to help better
understand the weather in northwest Mexico and the
southwestern United States…
33. Interannual variability of African monsoon
Wet 50-60s,
Dry 70-90s
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34. Warmer SST Weaker monsoon
Global warming
Dryer ??
