1.1 Problem Statement
Surface current is one of the important ocean information and the main component of the ocean circulation. By studying them, it will help scientist to understand their mechanism and time-variable characters, which useful for exploiting ocean resources, disaster prevention and mitigation, ship navigation and etc (Zhang, 20007). However, this aspect has not received enough attention in the region, due to various reasons and constraints. There are two weak points in ocean current study in Malaysia which encourage this study; limitation of data collection and data management problem. Besides of that, the ability of multi-mission satellite altimetry to provide long term sea level and wind data also motivate this study to understand further the seasonal variation of surface current pattern. It is because, the transitions of monsoon which can be distinguish based on the changes in the wind flow patterns, strongly influence the surface current pattern especially at open sea area such as South China Sea.
1.1.1 Data collection
Generally, basic observations of ocean current do exist in Malaysia based on in situ observational such as ship drift, drifting buoy or current metre. But in most cases, observations just cover limited areas and serve certain specific purpose. It isbecause direct measurement for large scale area is difficult and use costly basin scales. In Malaysia, there are two agencies which are responsible in carrying out the periodic observation on ocean current; Royal Malaysia Navy Hydrographical Department (RMNHD) and Malaysian Meteorological Department (MMD). However, as military agencies, the observation by RMNHD just most designed for military purpose and the data from the observations are not freely accessed by civilians. While, MMD just depends on four stations, Pangkor Island waters, Jetty of UMS, Kota Kinabalu, Mabul Island Semporna and Perhentian Island, Terengganu to collect the ocean current data. The observation can only provide point base data and not represent the offshore area because the stations just installed at coastal area. Thus, this limited information reveals some important features of the ocean circulation. An alternative to overcome those limitations is by using space-based technique to provide large-scale surface current and study the ocean circulation.
1.1.2 Data management
Malaysia is still facing problems with ocean data management. The ocean database in Malaysia can be said as not centralised because the data are normally kept separately in the different institution which carried out the observations. For example, RMNHD and MMD have their own database system. Other industries like oil and gas have also conducted ocean current observation and have developed their own database system. Additionally, the data are not representative for the whole Malaysian seas area and are just designed for their purpose respectively. Although there is effort by the Malaysian National Oceanography Directorate (NOD) to develop MyNODC (Malaysia Oceanographic Data Centre), a database for oceanographic data sharing, but until now the project is still not fully success because of data limitation and data sharing problem between institution and NOD. This situation make difficult for scientist to access the data for another scientific research. To overcome this problem, an oceanographic database based on altimetry technology can be developed as an alternative database or supporting to MyNODC. From the database system, ocean data can be freely extracted, analyzed or printout for another scientific purpose.
This study embarks on the following objectives:
1) To derive surface current in Malaysian Seas using multi-mission altimetry and gravity satellite in the periods of eight years (year 2000- year 2008)
2) To investigate long term seasonal variation of surface current pattern using averaged eight years data
3) To develop an Ocean Current Informatics System for the Malaysian region