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UNIVERSITI PUTRA MALAYSIA
COASTAL CIRCULATION OFF KUALA TERENGGANU
MAGED MAHMOUD MARGHANY
FPV 1994 1
COASTAL CIRCULATION OFF KUALA TERENGGANU
MAGED MAHMOUD MARGHANY
MASTER OF SCIENCE UNIVERSITI PERTANIAN MALAYSIA
1994
COASTAL CIRCULATION OFF KUALA TERENGGANU
By
MAGED MAHMOUD MARGHANY
Thesis Submitted in Fulfilment of the Requirements for the Degree of Master Science in the Faculty of
Fisheries and Marine Science, Universiti Pertanian Malaysia
September 1994
ACKNOWLEDGEMENTS
The author would like to thank the Almighty Allah for
making him be the first Arab, to do research on physical
oceanography in this part of the South China Sea, which
has been ignored by scientists. Everything has been done
by the action of Allah, who has given patience to the
author for continuing his study to a desire goal.
The author wants to express his gratitude and thanks
to his committee members Dr. Mohd. Nasir Saadon, Dr. Mohd.
Lokman Husain and Professor Dr. Mohd. Ibrahim B.Hj.
Mohamed for their all-round support, valuable suggestions
and encouragement without which would not have been made
possible.
The author also extends his thanks to the staff of
UNIPERTAMA I and UNIPERTAMA III boats especially Encik
Mohammed Embong and captain Rahman Muda who helped him to
collect the data under bad weather conditions of the sea.
ii
The support from the staff of the Faculty of Fisheries
and Marine science, Universiti Pertanian Malaysia in Kuala
Terengganu are also acknowledged especially Encik Sukiman
Sengat who supported him with basic programmes to calculate
temperature and salinity. Thanks are also to Encik Suliman
Kassim and Johari Mohamed.
The author thanks his friends Muhamad Saini, Mustapha
othman and Kamel Bahrin who prepare the figures in this
thesis. He also thanks his friend Rosland Salim who
translated the abstract to the Bahasa Malaysia.
Finally the author wants to express his deep gratitude
to Mr Cornelius Anwar Abdullah of Kolej Agama Sultan Zainal
Abidin in Kuala Terengganu who edited this thesis.
iii
TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS ii
L I ST OF TABLES viii
L I ST OF F IGURES ix
LIST OF PLATES xiii
ABSTRACT xiv
ABSTRAK xvi
CHAPTE R
I INTRODUCTION 1
Factors Inducing Water Circulation 1
II
III
Water Circulation in the South China Sea . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Problem and Importance of Water Circulation in Kuala Terengganu
Objectives
L I TERATURE REVI EW
Previous Work in the Study Area
Features of Water Circulation
Upwelling
Tidal Current
Residual Current
MATERIALS AND METHODS
Study Area
Sampling Design
iv
8
12
1 4
1 4
2 1
23
23
24
2 6
2 6
2 9
IV
V
Data Collection 3 2
Fi eld Wo rk and Observational Pro c edure . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2
Temperature Measurements 3 2
Sal inity Measurement s 3 6
Sampling Met hods 4 0
Temperature and Sal inity Distributions . . . . . . . . . . . . . . . . . . . 4 2
Current Measurements 4 2
Meteo rological Data 5 0
Tidal Data 5 1
RESULTS AND ANALYSI S 5 2
Temperature and Sal inity . . . . . . . . . . . . . . 5 2
Temperature Dist ribution 5 8
Sal inity Distribution 6 1
S urfac e Current 6 4
Sout h-west Monsoon 6 4
Transition Period 6 8
S ubsurface Current 7 0
Scatter Plots 7 2
Progressive Vector Plots 8 1
Component o f Current Velocity . . . . . 8 4
Tidal Current E l l ipses 9 0
Residual Current 9 0
DI SCUSSION 1 0 1
Temperature D i f f erences 1 0 1
Temperature Strati fication 1 0 4
v
VI
Sal inity Di f ferences 1 0 6
Water Sal inity Di stribution 1 1 3
Upwel l ing and Downwel ling 1 1 3
Surface Current 1 21
S urfac e Wat er Flow 1 2 1
Meander 1 2 3
S ubsurface Current 1 2 4
Subsurfac e Water Flow 1 2 4
Tidal Current 1 2 6
SUMMARY AND CONCLUSION 1 2 9
Temperature and Sal inity Distribution . . . . . . . . . . . . . . . . . . . . . . 1 2 9
Temperature Di f f erences
Sal inity Di ff erences
Water Stratification
Upwel ling and Downwel ling
S urfac e Current
Surfac e Current Flow
Meander
Subsurface Current
Subsurface Current Flow
Tidal Current
1 3 0
1 3 0
1 3 1
1 3 2
1 3 2
1 3 3
1 3 3
1 3 3
133
134
BIBLIOGRAPHY 1 3 6
APPENDI X
A Basic Computer Pro grams Used to Calculate True Temperature and Sal inity . ....... . 1 4 3
vi
B Fortran Computer Program Used to D raw I sothermal and I sohaline Contours .. . . . . . 1 4 8
C Fortran Computer Program Used to Draw progressive Vector Plots . . ... . ... . .... . 1 5 5
BIOGRAPHICAL SKETCH 1 5 9
vii
LI ST OF TABLES Table Page
1 . Maximum Current Speed during the Rising and Fal l ing Tide for E ach Observation Period . . . . . . . 7 6
2 . Summary of Average Ma j or Axis Speed and Minor Axi s Speed for Each Observation Period . . . . . . . . . 9 7
3 . Average Range of Residual Flow in the South-west and North-east Monsoon Periods . . . . . . . . . . . . . . . . 1 0 0
4 . Temperature Differences ( OC ) and their Average Value ( OC ) for E ac h Transect . . . . . . . . . . . . . . . . . . 1 0 2
5 . Sal inity D i f ferences ( ppt ) and their Average Value ( ppt ) for Each Transect . . . . . . . . . . . . . . . . . 1 0 8
viii
LI ST OF F I GURES
F igure Page
1 . Geographical Location of South China Sea ( From Pohlmann , 1 9 87 ) . . . . . . . . . . . . . . . . . . . . . 4
2 . Wind Stress Distribution in January ( From Hel l erman , 1 9 6 8) . . . . . . . . . . . . . . . . . . . . . . . . 6
3 . Wind Stress Distribution in July (From Hel lerman , 19 6 8) . . . . . . . . . . . . . . . . . . . . . . . 7
4 . Surface Current i n the South China Sea in the Month of February ( From Morgan and Val encia, 1 9 83 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5 . Surface Current in the South China Sea in the Month of August ( From Morgan and Valencia , 1 9 83 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0
6 . Study Areas Showing the Bottom Topography i n Kuala Terengganu Water . . . . . . . . . . . . . . . . . . . . . . 2 7
7. The Loc ation o f Stations i n Phase 1 for Col lection of Temperature , Sali nity , Current Meter and D rogue Deployment from May 1 9 9 2 to February 1 9 9 3 . . . . . . . . . . . . . . . . . . . . . 3 0
8 . The Location o f Stations Phase 2 for Temperature , Salinity and Current Measurements in the Month of March 1 9 9 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1
9 . Current Meter Deployment System . . . . . . . . . . . . . . . 4 5
1 0 . D rogue Deployment System
1 1 . Temperature and Salinity Pro f i l e s in Transect
4 9
1 for Each Observation . . . . . . . . . . . . . . . . . . . . . 5 3
1 2 . Temperature and Salinity Profiles in Transect 2 for Each Observation . . . . . . . . . . . . . . . . . . . . . 5 4
1 3 . Temperature and Sal inity Pro f i l es in Transect 3 for Each Observation . . . . . . . . . . . . . . . . . . . . . 5 5
1 4 . Temperature and Sal inity Pro f i l e s in Transect 4 for Each Observation . . . . . . . . . . . . . . . . . . . . . 5 6
ix
15 . Temperature and Salinity Profiles in Transect 5 for Each Observation . . . . . . . . . . . . . . . . . . . . . 5 7
16 . The Track of a Dri fting Drogue Re l eased on 2 0th June 19 9 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5
17 . The Track o f a Dri fting Drogue Rel eased on 2 1th June 19 9 2
18 . The Track of a Dri fting Drogue Re leased on 19th S eptember 19 9 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19 . The Track of a Dri fting Drogue Re leased at Station 3 from 4th to 6th Apri l 19 9 3 . . . . . . . . .
2 0 . The track of a dri fting drogue released at Station 5 f rom 7th to 9th April 19 9 3 . . . . . . . . .
2 1 . S catter Plots o f Current Speed against
6 6
6 7
6 9
7 1
Direction during South-west Monsoon Period 7 3
2 2 . Scatter Plots o f Current Speed against Direction during North-east Monsoon Period 7 4
2 3 . A Plot o f Maximum Current Speed against Tidal Height during the Rising Tide . . . . . . . . . . . . . . . . 7 7
2 4 . A Plot o f Maximum Current Speed against Tidal Height during the Fal l ing Tide . . . . . . . . . . . . . . . 7 7
2 5 . Scatter Plots of Wind Stress during the South-west Monsoon Season . . . . . . . . . . . . . . . . . . . . 7 9
2 6 . S c atter Plots o f Wind Stress during the North-east Monsoon Season . . . . . . . . . . . . . . . . . . . 8 0
2 7 . Progres sive Vector Plots during the South-west Monsoon Season . . . .. . . . . . . . . . . . . . . . . . . . . . . 8 2
28 . Progre ssive Vector Plots during the North-east Monsoon Season . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3
2 9 . U and V Current Speeds Components during the South-west Monsoon Season . . . . . . . . . . . . . . . . . . . . 8 6
3 0 . U and V Current Speeds Components during the North-east Monsoon Season . . . . . . . . . . . . . . . . . . . . 8 7
3 1 . A Plot o f Variance U Component against the Variance o f Tidal E l evation . . . . . . . . . . . . . . . . . . 8 8
x
32. A Plot o f Variance V Component against the Variance of Tidal E levat ion ................... 88
33. Tidal Current E l l ipses i n the Month o f May 1992 ......... "................................ 90
34. Tidal Current E l l ipses in the Month o f June 1992 .......................................... 91
35. Tidal Current E l l ipses in the Month o f July 1992 .......................................... 92
36. Tidal Current E l l ipses in the Month o f August 1992 ............................................. 93
37 . Tidal Current E l l ipses in t he Month o f October 1992 .................................. 94
38. Tidal Current E l l ipses in the Month o f March 1993 .......................................... 95
39. Tidal Current E l l ipses in the Month o f April 1993 .......................................... 96
40. Residual Currents for Each Observational Period ........................................ 98
41. The Net residual Current Flow f or Each Observation ................................ . .. 100
42. Temperature Distribution during the South-west Monsoon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
43. Rainfal l Distribution for Each Observational Period ( Malaysian Meteoro logical S e rv ice , 1 9 9 3 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 9
44. ( a ) Temperature and ( b ) Sal inity Distribut ion of Transect 1 in February 1993 ............. 110
45. Temperature D i stribution in Transect 5 Through August and october . . ...... . . . .... . ... . . . . .. . 112
46. Upwe l l ing Observation f rom ( a) I sotherm and ( b ) I sohaline Contours During South-west Monsoon ................. . .................. 115
47. Temperature and Sal inity Distribution in the Month o f May 1992 .. . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 7
xi
4 8 . Downwel l ing observation from ( a ) I sotherm and ( b ) I sohaline Contours During North-east Monsoon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 9
4 9 . Temperature Distribution in the Month of February 1 9 9 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 2
xii
LIST OF PLATES
Plate
1. The River Mouth o f Kual a Terengganu
page
Viewe d f rom the North . . . . . . . . . . . . . . . . . . . . . . . . . 2 8
2 . Reversing Thermometer 3 3
3 . Nansen Bott le . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4
4 . I n ductivel y Coupled Sal inometer Mo de l 6 0 1 Mkv . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 8
5 • UNIPERTAMA I I I 4 1
6 . ONO S e l f Recording Current Meter . . . . . . . . . . . . . . . 4 3
7 . Drogue Used i n this Study . . . . . . . . . . . . . . . . . . . . . . 47
xi i i
Abstract o f thesis submitted to the S enate o f Universiti Pertanian Malaysia i n ful fi lment of the requirements for the degree o f Master o f S cience
COASTAL C IRCULATION OFF KUALA TERENGGANU
By
MAGED MAHMOUD MI�RGHANY
SEPTEMBER 1994
Chairman Mohd. Nas ir Saadon,Ph.D
Faculty Faculty of Fisheries and Marine Science
The aim of this study was to determine the t ype o f
the current patterns i n the coastal waters o f Kua l a
Terengganu. This study was divided in two parts . The
first part was to determine the pattern of thermohaline
c irculation . This was done by s ampling 2 5 stations along
the coastal water of Kua l a Terengganu . The second part
was to measure the subsurface current by aNa-self
recording current meter and drogue .
The thermohaline c ircu l ation was dominated by
mixing during the north-east monsoon period ( October
1992, February and March 1993) due to the turbulence
xiv
resulting from the action of wind and tide . A dominant
feature of this study was the oc currence of upwe l l ing
during the south-west monsoon period ( May to August
19 9 2 ) . The do wnwe l l ing occurrences are in the north-east
monsoon .
The study showed that the subsurface current i n the
coastal waters of Kual a Terengganu were influenced b y
the tide . The current speed throughout this study varied
from 0 . 0 12 to 2 . 6 m/s . The tide throughout this study
was diurnal in nature . A dominant feature through this
study was tidal current whi l e , the winds have no impact
on the wate r movement . Fina l l y the data of surfac e
current i l l ustrated that the water meanders in the month
o f April 1 9 9 3 . Meande r rotated in c lo ckwise direction
from the no rth to south-west direction with an average
current speed of about 0 . 4 m/s .
xv
Abstrak tesis yang dikemukakan kepada Senat Universiti Pertanian Malaysia sebagai memenuhi keperluan untuk i jazah Master S ains .
PUSINGAN PERSISlRAN DI KUALA TERENGGANU
Oleh
MAGED MAHMOUD M'ARGHANY
SEPTEMBER 1 9 9 4
Pengerus i Mohd. Nas i r Saadon,Ph.D
Fakulti Fakulti Perikanan dan Sains Sarnudera
Tujuan kaji an ini a dalah untuk menentukan jenis corak-
corak arus di perairan pantai Kuala Terengganu . Kajian ini
dibahagikan kepada dua bahagi an . Bahagian pertama adalah
mengenai kitaran termoha li n . Ini di l akukan ke atas 2 5 buah
stesen kaji an sepan j ang perairan pantai Kuala Terengganu .
Bahagian kedua pula adalah untuk mengukur arus sub-permukaan
menggunakan meter arus " ONO s e l f recording" dan " drogue " .
Kitaran termohalin telah di dominasikan percampuran
khasnya semasa tempoh Monsun Timur Laut ( Oktober , 19 9 2 ;
Februari dan Mac , 19 9 3 ) akibat daripada penggeloraan hasi l
xvi
dari t indakan angin dan pasang surut . S atu c iri dominan
dalam kajian ini adalah kejadian julang air yang tinggi
semasa berlakunya Monsun B arat Daya ( Mei hingga Ogos , 1 9 9 2 )
berbanding dalam tempoh Monsun Timur Laut ( Oktober , 1 9 9 2 ;
Februari dan Mac , 1 9 9 3 ) . Tetapi , ke j adian junam air adalah
lebih kerap pada Monsun Timur Laut berbanding Monsun B arat
Daya .
Kajian ini menun j ukkan bahawa arus sub-permukaan di
perairan pantai Kuala Terengganu adalah dipengaruhi o leh
pasang-surut . Kel ajuan arus sepan j ang kaji an adal ah berubah
ubah dari 0 . 0 1 2 hingga 2 . 6 m/s . Pasang-surut sepanj ang
kajian adalah diurnal . Arus pasang-surut adalah ciri yang
dominan sepanjang kajian , sementara angin tidak mempunyai
kesan t erhadap aliran air . Akhirnya , data bagi arus
permukaan yang dipero lehi menggambarkan bahawa pembelokan
air berlaku pada bulan April 1 9 9 3 . Pembe lokan berlaku
mengikut arah jam dari arah utara ke barat-daya dengan
kelaj uan purata arus lebih kurang 0. 4 m/s .
xvii
CHAPTER I
INTRODUCTION
Factors I nducing Water Circulation
The study of the ocean is always a challen ging and
intri guing process considering its s i z e and the expanse
of the earth it cove rs . Features of sea c i rculation are
complex and a challenge for humans to comprehend . Al l
l i f e and c l imatical c hanges depend on c i rculation . The re
i s no doubt that water c i rculations of the world are
important to l i fe i n this planet . I t is not easy to
unde rstand water c i rculations because there are many
factors cont ro l l ing them . S c ientists cannot study the
factors separately as this wi l l give them an imperfect
answer.
Most scientists identi fy the forces whic h induce
c i rcul ations to be the wind ( Watten , 1 9 7 3 ; Gross , 1 9 7 7 )
and the t ide ( Horrer , 1 9 6 7 ) but there are many othe r
factors that p l ay a role in water c i rculations .
Many of the surface currents are wind driven . So
studies of water movements in the shal low coastal regions
1
as wel l as in the open sea
of atmospheri c forces , including
stress. Momentum exchange is the
require
2
knowl edge
pressure and wind
most di rect and
immediat e l ink between atmospheric and oceanic
c i rculations and occurs whenever wind blows over any part
o f t he sea. Some of the momentum causes turbulence drag,
or shearing stress between the water layers ( Bowden ,
1 9 60 ; Beer, 1 9 8 3 ) . The integrated action of wind system
resul t s i n a large-scale t ranslation of water masses .
Turbulence drag and shearing stress between water l ayers
disturb the seas inherent kinetic energy_ The influence
of the earth's rotation , on t he other hand , is the
p rimary driving force of the world ' s ma j o r current
systems such as the huge anticycl onic gyres ( Csanady ,
1 9 8 0 ) .
Density differences between water masses is another
dri ving force that induces water movement , usually the
ve rtical mo vements . The flow of the ma j or deep water
currents are caused by gravity pul ling the denser water
masses downwards , displacing lighter water masse s upward .
Since the density is cont rol led by the water tempe rature
and salinity , these currents are usually cal l ed
thermohal ine currents ( Horre r , 1 9 67 ; Pickard and Emery ,
1 9 8 2 ) .
The third factor that generates water mo vements i s
the tidal force. Being oscil l ato ry in nature the tides
cause net water movement which is averaged ove r a period
3 o f weeks or months . The re are other l arge scale currents
whic h are superimposed on this type of water movement .
Sma l l -scale o s c i l l atory currents c an sometimes be
observed whe re water is conf ined in harbours or estuaries
( Davis , 1 9 7 7 ) .
Water Circulation in the South China Sea
To understand the water movement pattern of Kual a
Terengganu , one should get more information about water
c i rculation i n the South China Sea. This is because,
Kual a Terengganu wat er is a part of the South China Sea
and there fo re knowing mo re about the water prope rties in
the South China Sea wi l l he lp researchers to unde rstand
the wate r c i rculation o f f Kuala Te rengganu .
The South China S ea i s the l argest water body i n
Southeast Asia ( Fi gure 1 ) . I t is surrounded by the Asian
continent , the I ndonesian Archipe lago , West Malaysia , the
Phi lippines and Formosa . The seafloor of the south china
sea can be divided into 3 dis tinc t areas . They are; (1)
Northern Sunda Shel f , ( 2 ) Gul f of Thailand and ( 3 ) China
sea basin .
The Northern Sunda S he l f extends between Sumatra and
B o rneo north eastwards as a narrow be lt ( 5 0 - 1 0 0 km ) along
the Asian Continent Borneo and Phil ippines. Average depth
of the shelf is 50 m with its deepest part at 10 0 m .
CHINA
SEA
China Sea
�N.ATUNA IS. 'l " - 4 .UU· ...... S ..
BORNEO
BASHI', CHAN�e:L
.0() � ( , D � "'N"""i\) Q " �-z,
� f· �� ('" • � T � ,J. �@jo �'. iP._ SULU qjI.!. .
I\AfABAC :; T"RAI T SEA '''OAHAO . 0 \..�OL'i? t-G c,0 't,.\..
... :.r.,\« �G " CELEBES 'I.
SEA "
Figure 1 . Geographical Location of South China Sea (From Pohlmann, 1987)
4
5
To the north-west is the Gul f of Thail and . The Gul f
i s about 4 0 0 km wide and i t has a maximum depth of 8 5 m .
The China Sea basin is the deepest part o f South China
Sea . This area is c haracteri z ed by a combination of
bathymetric features . Off the Sabah Coast is the Palawan
Trench with a maximum depth of 3 4 7 5 m. Away f rom the
Palawan Trench , the seafloor turn into a broad i rregular
p l ateau . This area posses numerous seamount and f ringing
reef s that protrude to the surface appropriately named
Dangerous Grounds ( Wyrtki 1 9 6 1 ) .
One of the main features of the South China Sea i s
i t s location i n the t ropical low latitudes , whic h have
two important e ffects on the c irculat ion . Firstly , the
reduction of the Corio l i s parameter near the equator
makes nonlinear and frictional force become increasingly
important . S econdly , the South China Sea is dominated by
the monsoon regime and i s strongly inf luenced by semi
annual reversing circulation o f the atmosphere ( Pohlmann ,
1 9 8 7 ) .
Figures 2 and 3 show the wind stress distribution in
January and July . I n January north-easterly winds prevail
over the who l e region with an average magnitude of 9 m/ s .
I n July the wind distribution i s total ly reversed .
Weaker southwesterly winds dominate over most parts o f
the South China Sea with an average magnitude of 6 mls
( He l l erman , 1 9 6 8 ; Pohlmann , 1 9 8 7 ) .
12-LAYEA SHELF-SEA-HOOEL
-- SOUTH CHINA SEA ----
12 15 20 2" 30 '40 50 ao 70 eo 100 120 '.,,0 I ISO 230 --... -.. --- -- .... t::> � VINO-STRESS (mPo)
Figure 2 . wind stress Distribution in January (From Hel lerman, 19 68)
6