1. Indian Monsoon Part 1 Compiled By – Dr. Bheekam Singh
Associate Professor,
Department of Geography,
Mihir Bhoj P.G. College, Dadri
Gautam Budh Nagar (U.P.)

2. Introduction Complex meteorological phenomena
Number of concepts about the origin of monsoon.
Climate and economy of India are completely driven by the monsoon winds.
Refers to a season in which wind system reverse completely

3. Name and Definitions
Phenomena first observed by the sailors and traders, when their boats were flicked by these winds
Arabs also came to India and observed this seasonal reversal of winds
They named it Monsoon on Arabic word Mausim means Season.
It can be said that these are seasonal winds in which there is a complete reversal of winds after every six months.

4. Name and Definitions By Chang-Chia-Cheng
“Monsoon is a flow pattern of general atmospheric circulation over a wide geographical area, in which there are clearly dominated winds in one direction, in every part of the region concerned, but this direction of wind is reversed or almost reversed from summer to winter and winter to summer.”

5. Regions of Monsoon
Mainly in Tropical area between 20 degree north to 20 degree south
India is a typical Monsoon region
Indian sub-continent and South east Asia including China, Japan and Korea.
Seasonal changes are also seen in USA, Carrabin Islands, Madagascar, East Africa, Guinea Coast and Australia

7. Conditions affecting Monsoon
Differential heating
Shift in ITCZ
High pressure area in east of Madagascar
Tibetan Plateau Heating in Summer
Movement of Jet Stream
Changes in pressure of Indian and Pacific Ocean (Southern Oscillation)

8. Measuring the Intensity of Monsoon
By computing the difference in Heating over Tahiti Island (Pacific) and Darwin (Australia)
Negative pressure differences
-Below average and late Monsoon
Positive Pressure Differences
- Good and On time Monsoon

9. 1.Differential Heating or Thermal Concept
By Halley 1686
Concept – Monsoon are the extended land and sea breeze on a large scale, produced by differential heating of continents and oceans.
Two conditions
Summer conditions
Winter conditions

10. Differential heating during Day and Night time

11. Summer Conditions High temp. in Northern Hemisphere
Low pressure area near Peshawar and
Lake Baikal
Northward Shift of ITCZ (concept)
Low pressure area in Indian subcontinent and High pressure area in Arabian and Pacific Ocean
Creation of Ocean to land pressure gradient

12. Change in the position of ITCZ

13. Wind Moves from High pressure to low pressure
Warm and moist wind, strike with land obstructions, hence

14. Winter Conditions Position of Sun and ITCZ shift southward
Hence, high pressure at Lake Baikal and Peshawar
Relatively high temp and low pressure at Indian and Pacific ocean.
Land to sea movement of winds but cold and dry

15. Criticism Low pressure area in Northern
hemisphere is not stationary, it
changes its positions and not only thermally induced.
If thermally induced then there would be anti monsoon circulation in upper atmosphere, which is absent
High temperature and low pressure starts in April, but no rain before June

16. Criticism
Modern meteorology seems to have a idea that Indian monsoon is not an orographic rainfall
There are not only two but four seasons India which are having different levels of rainfall and temperature
Role of latent heat from oceans is missed

17. Role of Tibetan Plateau
In 1973 – MONEX (Monsoon Expedition)
By Soviet Union and India
4 Russian and 2 Indian well equipped ships were sent into Arabian sea and Indian Ocean
Aim was to identify the phenomena of monsoon
Soviet meteorologists find out that Tibet plateau has a great importance in occurrence of monsoon
Already pointed out by P. Koteshwaram in 1958

18. Tibetan Plateau 600km wide in west and 1000 km wide in East
Enormous block of high ground as a formidable barrier
Receives 2-3 degree more isolation than surrounding area

19. Tibet Plateau most Important found by Indian but credit goes to Russian

20. Role of Tibet Plateau Effects in Two ways As a physical barrier
As a relatively high source of heat

21. As a physical barrier By Maung Tun Yin
ITCZ shift in north of Himalaya and Tibet in summer near 40 degree north
Relationship between shifting of ITCZ and slowing down of westerly jet stream
So opening of monsoon in June is a result of hydro dynamic effect of Himalayas not the thermally induced low pressure
Become very cold in October and create jets in its south as easterly

23. As a high level heat source
High heat and low pressure creates anticyclones
These anticyclones slow down the sub tropical jet streams but intensifies the tropical jets in south
These tropical jets extends westward from India to Arabian sea on Kolkata-Banglore axis
Create high pressure cell in Arabian sea and also called sinks into Arabian sea
Finally moves as South west monsoon

24. Hot Tibet with cool people

25. Role of Madagascar
The intense high pressure formed at east of Madagascar near 20 degree south in Indian Ocean cause the wind to flow towards the low pressure in India
Not continuous but temporary phenomena
Whenever there will be low pressure zone here in extreme conditions, monsoon in India will be weak

26. Madagascar is it Important?

27. Monsoon and SO
Normally there is high pressure in tropical east Pacific ocean and low pressure in Tropical Indian Ocean
In certain years there is reversal in pressure conditions
This periodic change in pressure condition is known as Southern Oscillation (SO)
The SOI is computed from fluctuations in the surface air pressure difference between Tahiti (Over Pacific Ocean) and Darwin, (Indian Ocean near Australia). El Niño episodes are associated with negative values of the SOI, meaning that the pressure at Tahiti is relatively low compared to Darwin.
This results in a decrease in the strength of the Pacific trade winds, and a reduction in rainfall over eastern and northern Australia.

28. Normal Condition
Extreme condition

29. Monsoon and El Nino (ENSO)
 In a typical ENSO, the strong easterly winds of the equatorial Pacific weaken,
which allows warm eastward-flowing subsurface waters to rise, increasing surface temperatures 1-2°C  and sometimes  in the central and Eastern Pacific.
Along the West coast of South America, El Niño's warm waters persist and deepen, and cold, upwelling, nutrient- rich waters fail to reach surface waters; the resulting warm, nutrient-poor waters devastate coastal fisheries.
Heavy rain falls along the South American coast, and heavy rainfall also moves from the western to central Pacific, causing drier than normal conditions in Indonesia and nearby areas including India.

31. Monsoon and Somalian Current
Somalian current change its flow direction at every six month
Generally low pressure zone
After every seven or eight years changes into high pressure area
Creates weeker monsoon over India