Faculty of Resource Science and Technology. Nur Asilah binti Awang

Transcription

1 Faculty of Resource Science and Technology Satellite and In-Situ Measurement for Temporal Variability of Sea Temperature in Talang Satang National Park Nur Asilah binti Awang Bachelor of Science with Honours (Aquatic Resource Science and Management) 2014

2 SATELLITE AND IN-SITU MEASUREMENT FOR TEMPORAL VARIABILITY OF SEA TEMPERATURE IN TALANG SATANG NATIONAL PARK NUR ASILAH BINTI AWANG This project is submitted in partial fulfillment of the requirements for the degree of Bachelor of Science with Honours (Aquatic Resource Science and Management) Department of Aquatic Science Faculty of Resource Science and Technology UNIVERSITI MALAYSIA SARAWAK 2014

3 Acknowledgement Praise to the most merciful Allah, for giving me strength, courage, and wisdom to write my final year thesis. Final semester has been tough to me personally, but after going through it all, I believe I can look back at my achievement and be proud of myself for what I have managed to do. Much thanks to my supervisor, Dr Aazani Mujahid, for all the guidance, encouragement, support and recommendation. Without you, completing this project would have been impossible. You were always there when I need you, and nothing that I can do will ever repay all the kindness that you have shown me. You are the best supervisor I could ever ask for, and I am always grateful for you. As for my beloved family, including my dearest friend, Mohd Efree Budiman (who is like a family to me), you guys have always been the sources of my strength, you have helped me a lot, so often that I lost count. Your supports and blessings are all I need in this life, and I will always pray for all your healthy and success. Last but not least, for all my lecturers, colleagues, postgraduate students, and lab assistants; I thank you all for your support and any sorts of help you have given me, either directly or indirectly. I apologize for not included your name here as they are too long for me to list out. All in all, I sincerely hope this thesis could be useful for anyone who wishes to seek information from it. May God bless you all. Cheers. II

4 Table of Contents Content Acknowledgement List of Abbreviations List of Figures List of Tables List of Appendices Abstract Page II V VII IX IX X 1.0 Introduction Literature Review Remote Sensing Remote Sensing and Sea Temperature Satellite Sensors Advance Very High Resolution Radiometer (AVHRR) Data logger and Other In-Situ Instruments South China Sea and Monsoon Climate Ocean and Climate El Niño Southern Oscillation (ENSO Materials and Methods Study Sites Sea Temperature Datasets In-Situ Sea Temperature Data Satellites Sea Temperature Data Data Analysis Results 16 III

5 5.0 Discussions Comparison of Satellite and In-Situ Sea Temperature of Talang Satang National Park (TSNP) Sea Surface Temperature Variability Seasonal Sea Surface Temperature Variability Interannual Sea Surface Temperature Variability ENSO Forecast Conclusion Recommendation and Future Study 37 References 38 Appendix 1 42 Appendix 2 44 IV

6 List of Abbreviations ANOVA AVHRR ENSO EA GAC GISS HadCRUT3 ITCZ LAC MEI MCSST NASA NCDC NE NW NH NOAA ONI SCS SE SW SH SEVIRI Analysis of Variance Advance Very High Resolution Radiometer El Niño Southern Oscillation East Asia Global area coverage Goddard Institute For Space Satellite global temperature series from Hadley Center Inter-Tropical Convergence Zone Local Area Coverage Multivariate ENSO Index Multichannel Sea Surface Temperature National Aeronautics and Space Administration National Climate Data Center Northeast Northwest Northern Hemisphere National Oceanic and Atmospheric Administration Oceanic Niño Index South China Sea Southeast Southwest Southern Hemisphere Spinning Enhanced Visible and Infrared Imager V

7 SST SOI TSNP Sea Surface Temperature Southern Oscillation Index Talang Satang National Park VI

8 List of Figures Figure Figure 1 El Niño region based on the location in the equatorial Pacific. Adapt from NCEP(2014). Page 11 Figure 2 Map shows the location of Talang Satang National Park (TSNP). 12 Figure 3 Flowchart for sea temperature datasets analysis 13 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Partial gridded image indicating the pixel for location of TSNP. Grid 2º x 2º = 400 km 2. Red pixel: TSNP location; yellow pixel: points for composite mean SST. These four points were averaged for the SST of TSNP (Mean TSNP SST = [(SST 1 + SST 2 + SST 3 + SST 4) / 4]. Sea temperature in Talang Satang National Park (TSNP) recorded by HOBO Pendant Data Logger. * Data is not available from August 2012 until March Variability of SST retrieved via satellite in TSNP. Trends were almost similar throughout the year showing TSNP was experiencing seasonal monsoon every year. * Mean SST is shown in bold line, while mean SST ± standard deviation (dotted line). Comparison of sea temperature between AVHRR and HOBO Pendant Temperature/Light Data Logger. Red (black) line represents the AVHRR (data logger) mean sea temperature. Most of the time AVHRR reading intercepts with the data logger reading and all of the readings are lower than the logger. *Data is not available from September 2012 to March Monsoon season with its corresponding months. Northeast monsoon (November-March), Southwest monsoon (May- September), and Inter-monsoon (April & October). Seasons changing as the earth circling the sun, passing through the orbit. The earth inclines 23.5º from its axis, causing unequal distribution of solar radiation between the hemispheres. Modified from Barry & Chorley, 1992). Monsoon wind patterns. ITCZ shift southwards during boreal winter (a) and northward during boreal summer (b). As the thermal equilibrium (ITCZ) shifts, Easterlies Trade wind deflected when it pass through the equator due to Coriolis Effect, thus forming Northeast monsoon and Southwest monsoon VII

9 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Comparison of light and sea temperature recorded from HOBO Pendant Light/Temperature Data Logger. * Data is not available from September 2012 to March Monthly sea surface temperature trends during monsoon season cycle. Alphabets represent Regime A, Regime B, Regime c, Regime D, Regime E, and Regime F. Mean SST of TSNP for 10 years period ( ). Graph shows apparent seasonal cycle throughout the year. Red box in the figure indicates significant different of SST ( ) trends compared to other years. Comparison of SST anomalies (ºC) of El Nino event (2009 to 2010) with the anomalies of El Nino predicted (2013 to March 2014). Diagram shows the process of transmitting electromagnetic radiation from the ocean to satellite sensor within the IFOV. Adapt from Robinson (2004). Electromagnetic spectrum showing the variation with wavelength of atmospheric transmission and the spectral windows used for remote sensing. Adapt from Robinson and Guymer (2002) VIII

10 List of Tables Table Page Table 1 Regimes with their corresponding months and temperature trends. 26 Table 2 Table 3 Table 4 Historical El Niño and La Niña episode based on the ONI. Pacific warm (red) and cold (blue) episodes based on a threshold +/- 0.5 ºC for the ONI. Threshold must be exceeded for a period of at least 5 consecutive overlay 3 months seasons. ONI more than +/- 1.0 ºC is considered as strong ENSO event. (Adapted from NCEP, 2014) Months that is significant than other years ( ) in Talang Satang National Park. Highlighted box indicates warm (red) months and cold (blue) months. General features of ENSO (warm and cold phase) with different strength in Talang Satang National Park Table 5 Specification of HOBO Pendant Temperature/Light Data Logger 43 Table 6 Table 7 Table 8 Descriptive statistics for sea temperature from HOBO Pendant Light/Temperature Data Logger Descriptive statistics for SST retrieved from AVHRR satellite sensor ( ) Pearson Correlation (r) between years ( ) for SST retrieved via satellite (r = 1 being the highest correlation). **. Correlation is significant at the 0.01 level (2-tailed) List of Appendices Appendix Page Appendix 1 Figures and Tables from Literature Review 42 Appendix 2 Figures and Tables from Results and Discussion 44 IX

11 Satellite and In-Situ Measurement for Temporal Variability of Sea Temperature in Talang Satang National Park Nur Asilah binti Awang Aquatic Resource Science and Management Faculty of Resource Science and Technology Universiti Malaysia Sarawak ABSTRACT Remote sensing is one of the important tools used to measure sea surface temperature (SST). The main purpose of this study is to determine sea temperature in Talang Satang National Park (TSNP) and to relate it with El Niño Southern Oscillation (ENSO). Sea temperature in TSNP is measured using HOBO Light/Temperature Data Logger and AVHRR satellite sensor. The mean sea temperature from data logger is ± 0.74 ºC, while the sea temperature from the satellite is ± 0.71 ºC. The reliability of SST retrieved from the satellite in TSNP is questioned. Consecutively, the satellite datasets for SST in TSNP is compared with data logger. There is high correlation between these two instruments (r = 0.792). Satellite managed to record the trends of SST, but not providing the absolute value. From the recorded trends, it shows TSNP is influenced by seasonal monsoon; namely the Northeast (NE) monsoon (November - March) and Southwest (SW) monsoon (May September). Monsoon caused the variability of SST. High SST recorded during SW monsoon and the transitional months, but low SST during the NE monsoon. There were double maximum peak of SST every year; highest in June, followed by October. The SST in the year 2008 to 2011 were significantly different than others due to strong ENSO event. Strong ENSO event gives impact to SW monsoon, which causes significant difference (p < 0.05) in SST during these periods. Forecasting ENSO event is possible only by several months ahead. SST anomalies from previous strong El Niño episode (2009) are compared with the prediction of El Niño (summer 2014). High correlation (r = 0.614) between these anomalies indicates the incoming El Niño may affect the SST in TSNP. Keywords: Sea surface temperature, satellite reliability, monsoon, ENSO ABSTRAK Penderiaan jarak jauh merupakan salah satu alat penting untuk megukur suhu permukaan air (SPA). Tujuan utama kajian ini adalah untuk mengetahui suhu air di Taman Negara Talang Satang (TNTS) dan untuk menhubungkaikannya dengan El Niño Southern Oscillation (ENSO). Suhu air di TNTS diukur menggunakan pengesan alat satelit AVHRR dan HOBO Light/Temperature Data Logger. Purata suhu air daripada data logger ialah ± 0.74 ºC, manakala suhu air daripada satelit ialah ± 0.71 ºC. Kesahihan pengesan alat satelit AVHRR di TNTS dipersoalkan. Oleh itu, data SPA di TNTS yang diambil daripada satelit dibandingkan dengan data daripada data logger. Terdapat korilasi yang tinggi antara alat pengukur ini (r = 0.792).Satelit berjaya merekod trend SPA, tetapi bukan nilai sebenar. TNTS diepengaruhi oleh musim monsoon, iaitu monsun Timur Laut (TL) (November Mac) dan monsun Barat Daya (BD) (Mei September). Monsun mengakibatkan perubahan SPA. SPA tinggi pada monsun BD dan bulan perantaraan, tetapi SPA rendah pada monsun TL. Terdapat juga dua puncak maksima pada trend SPA setiap tahun; paling tinggi pada bulan Jun, dan diikuti bulan Oktober. Perbezaan ketara pada SPA telah dikesan pada tahun berbanding tahun-tahun yang lain. Peristiwa ENSO yang kuat mampu memberi kesan pada monsun BD dan seterusnya menyebabkan perbezaan yang ketara (p < 0.05) pada SPA pada tahun-tahun tersebut. Ramalan peristiwa ENSO hanya boleh dilakukan beberapa bulan sebelumnya. Anomali SPA daripada episode El Niño (2009) telah dibandingkan dengan EL Niño (musim panas 2014). Korilasi yang tinggi antara anomali tersebut membuktikan El Niño yang akan datang ini berkemungkinan besar member impak pada SPA di TNTS. Kata kunci: Suhu permukaan air, kesahihan satelit, monsun, ENSO X

12 1.0 Introduction The ocean covers 98% out of the 70% of water in the earth. This large body of water has high specific heat that makes it able to absorb and store heat during the day and release it at night, causing global cooling and warming effect (Richard et al., 2007), thus stabilizing our climate system (Wells et al., 2002). In order to study and understand the oceans that we depend for our continued existence, one of the technologies invented by scientist and engineers that are widely used throughout the world is remote sensing. Remote sensing has provided spatially and temporally detailed measurements that concern the global oceanic and atmospheric environment. Nowadays, many researchers rely on this technology to observe the ocean. However, remote sensing such as satellite sensors and ocean colour are subjected to backscatter of radiation (Martin, 2004), depth limitation (Griffiths & Thorpe, 2002) and weather interference (Jensen, 2005). Scientists are forced to depend on other conventional methods for deeper water measurement of selected parameters (Griffiths & Thorpe, 2002). Hence, for research using satellites that involves waters deeper than a metre or so, it is necessary to clarify the difference between the satellite-retrieval data with the in-situ data. In response to global warming, the study of sea temperature has become essential for experts to determine the climate change of the planet. It is crucial to ascertain the value of sea temperature as it affects earth weather, ocean s dynamic and also the biochemical processes of living organisms, specifically aquatic organisms. Numerous studies regarding to this has been recorded such as related to El-Niño Southern Oscillation (ENSO) (Dewitte et al., 2012; Simard et al., 1985; Tarakanov & Borisova, 2013), primary productivity (Feng & Zhu, 2012), coral studies (Putnam & 1

13 Edmunds, 2011) and many others. This confirms that the sea temperature is highly influence and may gives impact to the environment and ecosystem. Measurement of temperature using satellite is one of the data accessible since 50 years ago, but it is not available for all places in the world, thus restricted the ability to direct measure of climate scale changes in the ocean (Wells et al., 2002). This study provides the variability of sea temperature mainly in Talang-Satang National Park (TNSP), where it is located in the Southern of South China Sea. Seeing as there were not many research have been conducted in TSNP related to sea water temperature, this research may add new information for future study. TSNP is influenced by seasonal wind (monsoon). Temperature is one of the parameters that are highly affected by monsoon (Liu et al., 2002; Tang et al., 2003). Ng (2012) has conducted a study in obtaining temporal variability of sea temperature using data logger in the same region as this study. In continuing this previous research, temporal variability of sea temperature will be analysed using both data logger and remote sensing. Therefore, the objectives of this study are: 1. To determine sea temperature in TSNP using satellite and data logger. 2. To compare satellite-retrieved temperature with temperature logged by data logger. 3. To determine the seasonal variability of sea temperature from satellite for the past 10 years until present ( ). 4. To determine the interannual variability of sea temperature from the satellite for the past 10 years until present ( ). 5. To investigate the possibility of year 2014 being El Niño using sea surface temperature anomalies. 2

14 2.0 Literature Review 2.1 Remote Sensing Remote sensing is the application of electromagnetic radiation to gain information about the ocean, land and atmosphere without being in physical contact with it (Martin, 2004). The sensors can range from camera to multispectral satellite scanner. The use of satellites has provides information that describes many global phenomena through the understanding of regional variability and global climate changes. For instance, consistent global maps of the SST distribution will show seasonal variations and patterns of global climate. Thus having long-term consistent data records is important to understand changes in marine ecosystem (Feng & Zhu, 2012) Measuring the ocean from space is a complex method. Point of measurement of the ocean is recorded by sensors corresponding to an average over the instantaneous field of view (IFOV), which the area of IFOV depends on the sensor capability (Robinson & Guymer, 2002). All objects emit and reflect electromagnetic radiation where the electromagnetic energy is generated by several mechanisms such as changes in the energy levels of the electron and thermal motion of atoms and molecules (Campbell & Wynne, 2011). Appendix 1: Figure 15 shows the satellite sensor first received the electromagnetic radiation from the ocean passing through the atmosphere within the IFOV, then it will process the signal before sending it to the ground station for other application (Robinson, 2004). Born and Wolf (1999) stated electromagnetic radiation behaves as electromagnetic wave. Appendix 1: Figure 16 shows the spectrum of electromagnetic wave and it s wavelength, which depends on the observing band or window. 3

15 The mainly used electromagnetic bands to measure the oceans are visible, infrared and microwave band (Martin, 2004). Visible band ( nm) depends on the daylight and it measures for as far as the light can penetrate into the ocean, which could exceed more than 10 m depth; while infrared band ( µm) is independent of daylight and it measures blackbody radiation that emit from the subsurface to the top of the sea surface; and unlike microwave, visible and infrared bands are restricted to cloud-free period (Martin, 2004). Microwave radiation below the frequency of 12 GHz has the probability to eliminate atmospheric contamination problem as the clouds and aerosols are transparent to it, thus providing a more reliable data (Chelton & Wentz, 2005). Unfortunately, measuring the ocean using microwave is usually specialized on surface roughness (Robinson & Guymer, 2002), which it will not be covered in this study. Atmosphere including air, water vapour and aerosols absorb most radiation at wavelength less than 350 µm (Robinson, 2004). Atmospheric particles and gases also altered the intensity and wavelength of the sun s energy, thus influencing the accuracy of interpreting satellite data (Campbell & Wynne, 2011). However, there are few bands where the atmosphere is fairly transparent. These bands are known as atmospheric window (Campbell & Wynne, 2011). The spectral window wavebands are visible ( nm), part of infrared (3.7 and region between µm) and microwave (10mm) (Robinson & Guymer, 2002). 4

16 2.1.1 Remote Sensing and Sea Temperature Water temperature is the measure of energy due to the motion of molecules, which are caused by solar heating, radiating and evaporating cooling of the sea water, wind and wave mixing (Martin, 2004). Sea surface temperature (SST) is directly related to the exchanges of heat, momentum and gases between the ocean and the atmosphere (Emery et al., 2003). It affects the atmosphere through its sensible and latent heat fluxed across air-sea interface, thus making it essential for climate research (Chelton & Wentz, 2005). Daily or seasonal heating or cooling may give impact to the sea temperature (Wells et al., 2002). Infrared satellites are sensors used to determine the SST (Robinson &Guymer, 2002). A lot of research has been conducted regarding SST variability using various types of sensors. Luis and Kawamura (2003) studied seasonal variability of SST in West India shelf using Advance Very High Resolution Radiometer (AVHRR) at 9km spatial resolution. They also did monthly calibration to determine cloud contamination and quality level of SST retrieval. In 2011, Wang et al. re-evaluate the reformation of global mean temperature series through combination of land surface temperature and SST observation by introducing three series from global temperature series from Hadley Center (HadCRUT3), National Climate Data Center (NCDC) and Goddard Institute for Space Studies (GISS). Sea water temperature may give impact to the ecosystem either directly or indirectly. For instance, McClanahan et al. (2007) acquire direct temperature reading from National Oceanic and Atmospheric Administration (NOAA) satellite images to investigate potential connection between the observed spatial temperature variations with coral mortality for post 1998 El Niño Southern Oscillation (ENSO) event in the East African Coastal Current System as coral mortality is influenced by sea temperature. Besides that, 5

17 diurnal SST due to day (warming) and night (cooling) influence carbon dioxide fluxes in the ocean, and Kettle et al. (2009) proved this through their research using SST obtained from Spinning Enhanced Visible and Infrared Imager (SEVIRI). Research comparing satellite with in-situ data was also performed to test the difference with the satellite-derived data. In 1999, Kumar et al. Concluded that data from Multichannel Sea Surface Temperature (MCSST) algorithm from NOAA agrees with the in-situ data from previous research of SST variability in Tropical Indian Ocean. Hughes et al. (2009), compared in-situ with gridded sea temperature datasets which they obtained from the combination of three different interpolated SST products. They used gridded SST to identify mean temperature at a specific position, and they found out that the SST products matched with the observed in-situ variability especially for a study with a time scale more than three years. As for Yu and Emery (1996), they validated satellite data obtained from AVHRR at 1.1 km spatial resolution with moored buoys data to determine the variability of SST in West Tropical Ocean. They stated cloud cover is a major problem in retrieving data form satellite. Therefore they did cloud filter methods to reduce the problem, which are (1) dynamic threshold method to remove most cloudy data, and (2) meridional threshold method to remove the rest of cloudy pixel. Based on a research conducted by Emery et al. (2003), there are a few things that need to be considered in comparing the satellite-derived data with the in-situ. One of them is the difference in depth for measuring temperature between these two approaches. Most comparison used moored buoys and ships, where they measured bulk SST (depths from 0.5 to 5 m below sea surface), while in contrast satellite only measures skin SST (depths of approximately 10 µm from sea surface). The lack of in-situ skin SST measurements caused uncertainty in satellite SST estimation as the satellite SSTs were adjusted to match a 6

18 selection of buoys SSTs, causing it to ignore the physics that connect the skin and bulk SSTs during calibration. Therefore, they concluded to have a better estimation of satellite SST, comprehensive validation program for in-situ skin SST measurement is important Satellite Sensors Most previous study conducted used sensors from NOAA and National Aeronautics and Space Administration (NASA) satellites, thus confirming that their datasets are reliable to use for this study Advanced Very High Resolution Radiometer (AVHRR) AVHRR is an infrared satellite sensor that is sun-synchronized, polar orbiting satellite, a cross track scanning system with 2700km swath width at nadir and different spatial resolution depending on the area coverage (Martin, 2004). Local area coverage (LAC) provides full resolution AVHRR data at 1.1 x 1.1 km, and this data may be resample to 4 x 4 km global area coverage (GAC) (Jensen, 2005). AVHRR detect blackbody radiation (Robinson, 2004), do mapping of both daytime and night-time clouds, snow, ice and SST, and it used band 4 (10.3 to 11.3 µm) and band 5 (11.2 to 12.5 µm) spectral resolution specifically for SST mapping (Jensen, 2005). AVHRR is an operational system that gathers data frequently (Cracknell, 1997) as it complete global coverage within 24 hours and it orbits the earth 14.1 times daily (Campbell & Wynne, 2011). This sensor is widely utilized to study SST as its thermal bands are less noisy than some other instruments, and the data can be received in real time and processed within a very short time providing us near realtime SST maps (Cracknell, 1997). These have made AVHRR as a very informative instrument for researcher to obtain data for SST studies. 7

19 2.2 Data Logger and Other In-Situ Instrumentations Data logger has depth limitation and the limitation depends on the type of logger used. For example, HOBO Pendant Temperature/Light Data Logger has depth limit to 30 m in -20ºC to 20ºC (Appendix 1: Table 5). Due to this, it is not listed among popular equipments used to study the sea temperature. Nonetheless, if the area of interest is situated in shallow water, such as the coastal area, subsequently data logger may be one of the best options we have for its high resolution in measuring the sea temperature. Furthermore, it is small and light weighted, making it easily installed anywhere. In spite of this, not much study has been conducted using data logger as an instrument to record in-situ data for sea temperature. According to Emery et al. (2003), measuring the SST was started off with the use of sailing vessel where the temperature was measured with mercury in glass thermometer from a bucket of water that was collected while the ship was underway. Then evolution brings out an alternative method which is by mounting thermistors on the metal hull of the ship, followed by the use of remote sensing. The use of thermistors has been applied by Malcolm et al. (2011), in studying the spatial and temporal pattern of shallow-water sea temperature in Solitary Island. They also used it to determine whether temperature pattern using thermistors correspond with spatial distribution of the East Australia Current (EAC) examined from SST images obtained from AVHRR at 1km spatial resolution. Eventually, data logger became famous. One of the researches conducted was by Putnam and Edmunds (2011), where they used HOBO logger for measuring sea temperature at 10m depth to study the effects of fluctuating temperature on corals in Back Reef of Moorea, French Polynesia. More advance research was carried out by McClanahan et al. (2007), in which they combined sea temperature data recorded by HOBO 8

20 temperature logger with SST data retrieved via satellite to study sea temperature effects on coral reefs in East African Coastal Current system. 2.3 South China Sea and Monsoon Climate According to Liu et al. (2002), South China Sea (SCS) is the largest marginal sea with wide continental shelves and received voluminous runoff from several large rivers. It is situated at the centre of the Asian-Australian monsoon, where it joins four monsoon subsystems; namely East Asia monsoon, Tropical Indian monsoon, Western North Pacific monsoon and Australian monsoon (Wang et al., 2009). The climatic variation in SCS is controlled by the East Asian monsoon (Wang et al., 2009). Monsoon season is characterized by the high distribution of rainfall (Yen et al., 2014). It happens when land heats more rapid than the ocean, the ocean blow cold air toward the land, and continue heating caused the air to rise, forming clouds and eventually rainfall (Garrison, 2002). The surface circulation in the SCS drastically changes in response to the alternating monsoon. Summer monsoon takes place within late May to September; winter monsoon is between November and March, while April and October are the transitional months between these two monsoons (Yen et al., 2014). This seasonal cycle and circulation are driven by the seasonal winds associated with monsoon which influences both temporal and spatial distribution of SST (Liu et al. 2002; Palacios, 2004). 2.4 Ocean and Climate According to Charnock (2002), ocean and atmosphere circulation is considered as a single system, where the general circulation of this system is resolved by the distribution energy that comes from the sun (in term of solar radiation). He stated almost half of the solar radiation is absorbed by the earth s surface, specifically by the ocean. To rationalized the 9

21 coupled system of ocean and atmosphere, it can be briefly explained by this; first most energy radiates from the sun are absorbed by the earth surface (ocean), then this energy is used to evaporates the water from the ocean to the atmosphere, and the latent heat released from this process is used for the condensation of water to form cloud, and later leads to precipitation (Barry & Chorley, 1992). The heat and water vapour is converted by complex process into depression and cyclone or anti-cyclone; the winds of which that give energy to generate ocean waves and driven ocean current (Charnock, 2002) El Niño Southern Oscillation (ENSO) One of the most vital climate studies is the El Niño Southern Oscillation (ENSO) phenomenon. ENSO is known as a natural oscillation of the ocean-atmosphere system in the tropical Pacific Ocean and the interaction between this system results in the changes of SST (Wells et al., 2002). ENSO is named due to the interactions of El Niño and Southern Oscillation phenomenon (Chiew et al., 1998). Prior to El Niño, high and low pressure centers in the equatorial Pacific Ocean fluctuates, and this atmospheric phenomenon is known as Southern Oscillation (Piechota et al., 1997). Southern Oscillation term is used to portray the rise and fall of the east-west seesaw surface pressure in the southern Pacific (Hall et al., 2001). As the trade winds deteriorate in central and western Pacific during El Niño, it causes depression of thermocline in the eastern Pacific (Garrison, 2002). Subsequently, warm water pool from the western Pacific Ocean moves toward eastern, specifically at the coastal of Peru and Ecuador (Chiew et al., 1998). ENSO cycles oscillate between warm and cold phase; namely El Niño and La Niña respectively (Azmoodehfar & Azarmsa, 2013). This phenomenon usually implicates with 10

22 dramatic climate event such as annual fire occurrence and area burned (Simard et al., 1985), unusual rainfall, drought, flood and streamflow in certain country (Chiew et al., 1998), health impact (Zhang et al., 2007) and many others. Forecasting ENSO phenomenon generally will use indices such as Southern Oscillation Index (SOI), Oceanic Niño Index (ONI) and Multivariate ENSO Index (MEI). SOI calculated from the difference in atmospheric pressure between Tahiti in the Pacific and Darwin in Australia (Zhang et al., 2007), ONI is based on the 3 months running-mean of SST departures in Niño 3.4 region (NCEP, 2014), while MEI is derived on sea level pressure, zonal and meridional components of the surface wind, SST, surface air temperature and total cloudiness fraction of the sky (Azmoodehfar & Azarmsa, 2013). Figure 1 below shows the region of El Niño by the location in the equatorial Pacific Ocean. Figure 1: El Niño region based on the location in the equatorial Pacific. Adapt from NCEP(2014). 11

23 3.0 Materials and Methods 3.1 Study Sites Study was conducted at Talang-Satang National Park (TSNP) which includes both Talang- Talang Island (N 01º , E 109º ) and Satang Island (N 01º , E 110º ). TSNP is situated in the southern of South China Sea (SCS) and northern of Sarawak, Malaysia (Figure 2). It is one of Marine Protected Area for conservation of turtle and coral reefs. This study site was chosen based on the availability of existed dataset. Figure 2: Map shows the location of Talang Satang National Park (TSNP). 12

24 3.2 Sea Temperature Datasets Data for sea temperature was collected by using two different instruments; remote sensing and in-situ. Figure 3 shows the flowchart for sea temperature analysis Sea Temperature Data Data Logger 10 minute interval raw data AVHRR Satellite Sensor Monthly end user data Resolution 10 minutes Temporal 24 hours < 10 cm Spatial 4 km x 4 km Data Analysis Filtered by weekly and monthly Averaged monthly means Descriptive Statistics Mean, standard deviation, max/min value, mean difference Advance Statistics Pearson correlation test T-test One-way Analysis of Variance (ANOVA) Figure 3: Flowchart for sea temperature datasets analysis 13