Group Presentation Semester 03 ER2412 Introduction to Oceanography Department of Earth Resources Engineering University of Moratuwa This presentation is based on ocean currents in the world,sri lanka and monsoon system in sri lanka

1. Monsoon system
and
Ocean currents
around
Sri Lanka.
ER2412 Introduction to Oceanography
Department of Earth Resources Engineering
University of Moratuwa
GROUP 2

2. GROUP MEMBERS -(GROUP 2)
• D.L.P.M Dauglas - 110806L
• K.T.D Dissanayake - 110807P
• H.R.W Fernando - 110808U
2

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CONTENT
1. Ocean currents & Classification …?
2. Surface currents …
3. Formation of surface currents …
4. Deep water currents …
5. Formation of deep water currents …
6. Ocean currents around Sri Lanka …
7. Why is ocean circulation important …?
8. Measuring surface currents …
9. Measuring deep water currents …
10. What is Monsoon …?
11. Classification of monsoons …
12. Where can we see monsoons ...?
13. How is monsoon formed around Sri Lanka
(Indian ocean) …
14. Monsoon wind direction around Sri Lanka …
15. Importance of monsoon around Sri Lanka
(Indian ocean) …
16. Impacts of monsoon around Sri Lanka …
17. Methods of Predicting Monsoon Rainfall around
Sri Lanka …

4. Ocean currents …
1. Surface currents
2. Deep water currents
4
Ocean currents is affected to occur large scale water mass
movements and it is occurred everywhere in ocean both surface
and deep.
Stream like movement of ocean water that follows a regular
pattern.
Classification …

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Surface currents …
 Horizontal stream like movements of water that occur at the
surface of the ocean.
 Affect surface water within and above the pycnocline
(10% of ocean water) (upper 400m)
 Driven by major wind belts of the world
 Length 1000-2000Km
The following factors are caused in forming surface currents
1. Global winds
2. Coriolis effect (The Earth’s rotation)
3. Thermal expansion
4. Continental deflection and Etc.

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– Near the equator the trade winds blow ocean water to west
– Westerlies blow ocean water west to east
Formation of Surface Currents …
1. Global winds
Wind is the primary factor in forming Surface Ocean Currents.
Wind transfers some of its energy to the water by friction .

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2. The earth’s rotation (Coriolis effect)
 Currents move the oceans in a circular direction because the earth is
rotating. This is known as Coriolis effect.
 The earth’s rotation causes winds to curve clockwise in the northern
hemisphere, and counterclockwise in the southern hemisphere.
Thus Changes with latitude.
- No Coriolis effect at Equator
- Maximum Coriolis effect at poles

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This results in the large semi-circular gyres in each ocean basin.
Gyres: the circular pattern that develops from the combination of westerly
and easterly wind

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 North Pacific
 South Pacific
 North Atlantic
 South Atlantic
 Indian
Five main gyres (one in each ocean basin)

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Wind-driven surface currents

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3. Thermal expansion
 Equatorial surface waters receive more solar radiation than polar surface
waters
 Warm water currents: begin near the equator and carry water to other
parts of the ocean.
 Cold water currents : begin closer to the poles and carry cool water to
other parts of the ocean.
Sun

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4. Continental Deflections
 Basically, the currents are constantly being pushed by winds.
 Well, as their being pushed, they sometimes run into a continent.
 When surface currents meet continents, the current deflects ,or changes
direction and the continues.

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 Under water movements in the ocean.
 Affect deep water below pycnocline. (90% of ocean water)
 Form in sub polar regions at the surface.
 Are created when high density surface water sinks.
 Larger and slower than surface currents.
 Caused by differences in density.
- Influenced by changes in temperature and salinity.
 Deep currents are also known as thermohaline circulation
Deep water currents (thermal currents) …
↓ 𝐓𝐞𝐦𝐩𝐞𝐫𝐚𝐭𝐮𝐫𝐞 =↑ 𝐃𝐞𝐧𝐬𝐢𝐭𝐲
↑ 𝐒𝐚𝐥𝐢𝐧𝐢𝐭𝐲 =↑ 𝐃𝐞𝐧𝐬𝐢𝐭𝐲

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Deep ocean characteristics …
Conditions of the deep ocean:
 Cold
 Still
 Dark
 Sparse life
 Extremely high pressure

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Density layers in the ocean …
low density water overlies the pycnocline
Relatively warm
2% of ocean water
Density increases rapidly with depth
Temperature decreases rapidly with depth
18% of ocean water
High dense water
Cold
80% of ocean water
Pycnocline – the layer between surface zone waters and deep zone waters ,
Where a rapid change in temperature, salinity and density occur
Vertical structure of the ocean

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Formation of deep currents …
1. Decreasing temperature
 Water molecules cool down and move close together.
 Water become denser.
 Water sinks and travels toward the equator.

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2. Increasing salinity through freezing
 Ocean water freezes at surface.
 Dissolved solids squeezed out and enter liquid water below.
 Increases salinity of water.
 Density is increased and form currents towards equator.

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3. Increasing salinity through Evaporation
 Evaporation of surface water. (removes water and leaves
behind solids)
 Increases density
 Denser water sinks to ocean floor and forms deep currents.

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Global Conveyer-belt circulation …
 Large scale pattern to the way that sea water moves around the global ocean.
 Driven by changes in water temperature and salinity that change the density of
water.
 It affects water at the ocean surface and all the way to deep ocean.
 It moves water around the world.

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The global ocean …
 The world has several oceans, and while they have different names, they are
not really separate.
 There are no walls between oceans
 Water is able to move freely between them.
They are all
one Global ocean

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Ocean currents around Sri Lanka …
SC- Somali Current;
EC-Equatorial Current
SMC-Summer Monsoon Current
WMC- Winter Monsoon Current
EICC-East India Coastal Current
WICC-West India Coastal Current
SECC-South Equatorial Counter Current
EACC-East African Coastal Current
SEC-South Equatorial Current
LH-Lakshadweep high
LL-Lakshadweep low
GW-Great Whirl
Northeast monsoon Southwest monsoon

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Northeast monsoon Southwest monsoon

23. Why is Ocean Circulation Important …?
 Transport approximately 20% of latitudinal heat Equator to poles
 Matter Transport (Transport nutrients and organisms)
Currents also involved with gas exchanges, especially O2 and CO2
Nutrient exchanges important within surface waters (including outflow from
continents) and deeper waters (upwelling and down welling)
 Influences weather and climate
 Influences commerce
Impact on fisheries and other resources
 Transport of ships
Ships that transport goods, use surface currents to deliver their goods faster.
 Global warming could disrupt this current
 Pollution dispersal
23

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Why is Ocean Circulation Important …?

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Measuring surface currents …
Direct methods - Float meters (Intentional, Inadvertent)

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Direct methods - Propeller meters

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Indirect methods - Doppler flow meters

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Indirect methods - Radar altimeters.
Other methods - Pressure gradients
geostrophic currents derive from TOPEX/Poseidon sea-level anomalies.

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Measuring deep currents …
 Floating devices tracked through time
 Chemical tracers
- Tritium
- Chlorofluorocarbons
 Characteristic temperature and salinity
- Deep currents are identified by measuring temperature (T) and salinity(S),
from which density can be determined

30. Monsoon system
around
Sri Lanka.

31. What is Monsoon ...?
 ‘A name for a wind system that changes in speed and direction
with season.’ (derived from an Arab word)
 Monsoons are strong, often violent winds that change
direction with the season.
 Monsoon is a term derived form the Arabic word “Mausim”,
meaning season. It was first used by Arabic navigators to
describe the seasonal winds of the Arabian Sea.
31

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The global surface monsoons contains three kinds of monsoons:
1. Tropical monsoons
2. Subtropical monsoons
3. Temperate-frigid monsoons
Classification of monsoons ...

33. Where can we see monsoons ...?
Monsoons occur every year in many countries around the
world other than northern Australia, Africa, South America,
many regions in North America and Europe .
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34.  Asian monsoon -
(the largest monsoon)
India
Sri Lanka
Bangladesh
Indonesia and etc
 African monsoon
 South American monsoon
 North American monsoon -
Southwest United States monsoon
Mexican monsoon
Arizona monsoon
 N.W Australian monsoon 34
Tropical monsoons
Subtropical monsoons

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How is monsoon winds formed around Sri Lanka (Indian ocean) …
The major controlling factor over a tropical monsoon climate is its
relationship to the monsoon circulation. The monsoon is a seasonal change
in wind direction.
During Cold –High Density
During Summer –Low Density

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 In cold season (Winter): Cool dry winds blow from land to ocean.
 In warm season (Summer): Warm wet winds blow from ocean to land .
transport lot of moisture ,large rainfall
Monsoon winds blow from cold to warm regions because cold air takes up
more pressure than warm air.
Ocean Land
H L
HL
cold
warm
wet
Ocean Land
HL
H L
warm
cold
dry
Summer SeasonWinter Season

37. 1. The South –West monsoon (Summer monsoon) [May-September]
monsoon has warm winds blowing from Indian Ocean. These winds are
much stronger than during the winter monsoon.
2. North- East monsoon (Winter monsoon) [November-February]
monsoon is characterized by a dry continental air mass blowing from the
vast Siberian high pressure area.
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 These winds blow from the north-east for one half of the year and
from the south-west for the other half.
 In tropical monsoon country(E.g. Sri Lanka , India) there are two
major monsoon seasons.

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SW Monsoon NE Monsoon

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SW Monsoon NE Monsoon

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SW Monsoon NE Monsoon

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SW monsoon rains rich in moisture, are drawn towards the Himalayas creating
winds blowing storm clouds towards the subcontinent.
A fully illuminated views of the Indian
Ocean region shortly after the onset of
the SW Monsoon.

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March & April and October being the months of transition with weak winds
called Inter Monsoons. (before and after major monsoons)
Around Sri Lanka, two inter monsoons are occurred.
1. First Inter-monsoon [March & April]
2. Second Inter-monsoon [October]

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Monsoon winds direction around Sri Lanka …

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Direction of monsoon winds around Sri Lanka (Indian ocean) …

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Average monthly rainfall in Sri Lanka …

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Average monthly mean temperature in Sri Lanka …

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Season Coefficient of Variation of all Sri
Lanka Rainfall
1931 – 1960 1961 - 1990
Northeast Monsoon (Dec. to Feb.) 31% 42%
First Inter monsoon (Mar. to Apr.) 23% 27%
Southwest Monsoon (May. to Sep.) 21% 16%
Second Inter monsoon (Oct. to Nov) 22% 23%
Annual (Jan. to Dec.) 12% 14%
The Coefficient of Variation of all-Sri Lanka Rainfall during the periods 1931-1960 and 1961-1990

48. Climatological Seasons
1. First Inter-Monsoon (FIM) [March & April]
2. Southwest Monsoon (SWM) [May – September]
3. Second Inter-Monsoon (SIM) [October & November]
4. Northeast Monsoon (NEM) [December – February]
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Sri Lanka has four climatological seasons basically based on
monsoon rains

49. Importance of monsoons around Sri Lanka …
 Water management
- the reservoirs are filled and contain water is used to non-monsoon seasons
 Energy
- the reservoirs are filled and hydro electric projects find the going easier
 Agricultural efficiency
- farmers depend on the rains to irrigate their land
 Disaster mitigation
- fills up the dried up ponds and makes the habitat in forests more conducive to
wild life
 Water cools the earth surface and brings down the temperature
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Important About 60% of the world’s population depends on monsoons.

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If monsoons winds
blow around these
regions,
these disasters
are ended

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Impacts of monsoons around Sri Lanka …
 Floods
 Landslides
 River banks erosion
 Interrupt some day to day works
 Heavy monsoon is caused
damage agricultural crops
 Problem of soil erosion

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Methods of Predicting Monsoon Rainfall around Sri Lanka …
 Studies of historical data sets, over the years, have brought out several
predictors for the monsoon rainfall forecasting.
- The most commonly used statistical technique for seasonal predication is
the linear regression analysis.
 Behavior of blowing clouds view of the Indian Ocean region
Season Coefficient of Variation of
all Sri Lanka Rainfall
1931 –
1960
1961 - 1990
Northeast Monsoon (Dec. to
Feb.)
31% 42%
First Inter monsoon (Mar. to
Apr.)
23% 27%
Southwest Monsoon (May. to
Sep.)
21% 16%
Second Inter monsoon (Oct. to
Nov)
22% 23%
Annual (Jan. to Dec.) 12% 14%

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References …
 D. Shankar, P.N. Vinayachandran, A.S. Unnikrishnan (2013,July 20).The monsoon currents in the
north Indian Ocean[Online].Available:
http://eprints.iisc.ernet.in/18451/1/Progress_in_Oceanography.pdf
 E. M. Savithri (2013,July 20).Meteorological Setting of Sri Lanka[Online].Available :
Ranasinghehttp://archive.cmb.ac.lk/research/bitstream/70130/3804/1/emsr.pdf
 Earth (2013,July 21).Ocean Currents and Climate[Online]. Available :
http://earth.usc.edu/~stott/Catalina/Oceans.html
 Kanthi Kasyapa (2013,July 21). Seasonal variability of sea surface chlorophyll-a of waters
around Sri Lanka [Online]. Available :
http://www.ias.ac.in/jess/dec2000/E1412.pdf
 Meteorological Department (2013,July 21). Climate in Sri Lanka [Online]. Available :
http://www.meteo.gov.lk/index.php?option=com_content&view=article&id=106&Itemid=81..

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THANK YOU…