Monsoon system and

Ocean currents around

Sri Lanka.

ER2412 Introduction to OceanographyDepartment of Earth Resources Engineering

University of Moratuwa

GROUP 2

GROUP MEMBERS -(GROUP 2)

• D.L.P.M Dauglas - 110806L

• K.T.D Dissanayake - 110807P

• H.R.W Fernando - 110808U

2

3

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 …

Ocean currents …

1. Surface currents

2. Deep water currents

4

Ocean currents is affected to occur large scale water massmovements and it is occurred everywhere in ocean both surface and deep. Stream like movement of ocean water that follows a regular pattern.

Classification …

5

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 winds2. Coriolis effect (The Earth’s rotation)3. Thermal expansion 4. Continental deflection and Etc.

6

– 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 .

7

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

8

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

9

North Pacific

South Pacific

North Atlantic

South Atlantic

Indian

Five main gyres (one in each ocean basin)

10

Wind-driven surface currents

11

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

12

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.

13

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

14

Deep ocean characteristics …

Conditions of the deep ocean:

Cold

Still

Dark

Sparse life

Extremely high pressure

15

Density layers in the ocean …

low density water overlies the pycnoclineRelatively warm2% of ocean water

Density increases rapidly with depthTemperature decreases rapidly with depth18% of ocean water

High dense waterCold 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

16

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.

17

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.

18

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.

19

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.

20

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

21

Ocean currents around Sri Lanka …

SC- Somali Current; EC-Equatorial CurrentSMC-Summer Monsoon CurrentWMC- Winter Monsoon CurrentEICC-East India Coastal CurrentWICC-West India Coastal Current

SECC-South Equatorial Counter CurrentEACC-East African Coastal CurrentSEC-South Equatorial CurrentLH-Lakshadweep highLL-Lakshadweep lowGW-Great Whirl

Northeast monsoon Southwest monsoon

22

Northeast monsoon Southwest monsoon

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 shipsShips that transport goods, use surface currents to deliver their goods faster.

Global warming could disrupt this current Pollution dispersal

23

24

Why is Ocean Circulation Important …?

25

Measuring surface currents …

Direct methods - Float meters (Intentional, Inadvertent)

26

Direct methods - Propeller meters

27

Indirect methods - Doppler flow meters

28

Indirect methods - Radar altimeters.

Other methods - Pressure gradients

geostrophic currents derive from TOPEX/Poseidon sea-level anomalies.

29

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

Monsoon system around

Sri Lanka.

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

32

The global surface monsoons contains three kinds of monsoons:

1. Tropical monsoons2. Subtropical monsoons3. Temperate-frigid monsoons

Classification of monsoons ...

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 .

33

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 monsoon34

Tropical monsoons

Subtropical monsoons

35

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

36

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

coldwarm

wet

Ocean Land

HL

H L

warmcold

dry

Summer SeasonWinter Season

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.

37

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.

38

SW Monsoon NE Monsoon

39

SW Monsoon NE Monsoon

40

SW Monsoon NE Monsoon

41

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.

42

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]

43

Monsoon winds direction around Sri Lanka …

44

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

45

Average monthly rainfall in Sri Lanka …

46

Average monthly mean temperature in Sri Lanka …

47

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

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]

48

Sri Lanka has four climatological seasons basically based on monsoon rains

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 temperature49

Important About 60% of the world’s population depends on monsoons.

50

51

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

52

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

53

54

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%

55

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..

56

THANK YOU…