How Do We Measure Coastal Currents of Penang?

1. Where is Penang?

Penang is a Malaysian state located on the northwest coast of Peninsular Malaysia, separated from the mainland by the Penang Strait. The state is very famous for its vibrant culture, rich history, and breathtakingly beautiful landscapes.

Geographically speaking, Penang can almost be described as a kind of utopia. Penang Island is one of the major tourist destinations; its capital, George Town, stands as a UNESCO World Heritage Site. It is a combination of colonial architecture and street markets with all kinds of cultural attractions. The local population is multicultural, mixing Malays, Chinese, Indians, and many other ethnic groups, giving to Penang its unique cultural flavor.

The Penang Strait, which lies adjacent, is a small body of water that significantly imparts its role in the region's maritime activities. On one side, it is enclosed with a mainland and on another lies the island of Penang. The Penang coasts are characterized by sandy beaches, rocky shores, and extensive mangrove forests. The mangroves form part of the ecosystem and provide a habitat for many marine life species, such as crabs, fish, and birds. Besides that, many other marine life species can also be found in the strait waters; these include colorful corals and various species of shellfish.

2. What is the situation of the coastal currents near Penang?

The coastal currents in the Penang area are influenced by a number of factors. The tidal currents are one of the major forces. Gravitational pull from the moon and sun governs the tides in the Penang Strait. This produces a semi-diurnal tide-that is, two high tides and two low tides each day. Tidal currents will vary in strength and direction with phase of tide and local topography.

The monsoon winds have a considerable Say, too. During the southwest monsoon, generally from May to September, strong winds are carried on that can drive the surface currents in a particular direction. These change during the northeast monsoon from November to March, which changes the wind patterns and with them the direction and speed of coastal currents.

Other very important factors that need to be taken into consideration are the local bathymetry or underwater topography. The shape of the seabed, with underwater ridges, channels, and shoals, is able to redirect and modify the flow of the coastal currents. Another influence could be the discharge of rivers and streams into the strait, which can also affect the currents. Density differences created by freshwater input from these sources can sometimes give rise to rather complex current patterns.

3. How to observe the coastal water flow of Penang?

These are some of the methods used in observing the flow of water in the coasts of Penang. One of the more straightforward yet efficient methods is the surface drifting buoy method. A buoy is set into the water with attached Global Positioning System or other tracking devices. As the buoys get carried by the currents, movements are monitored over time to determine the direction and speed of the currents in the surface.

In the anchored ship method, a ship is anchored at a place and current-measuring instruments record the flow of water at different depths. However, this technique suffers from certain drawbacks. The ship undergoes the effects of waves and winds, and incorrect readings may result. Apart from this, it is not very efficient for covering a big area.

The ADCP method is a far more futuristic and efficient way of measurement for coastal water flow. By applying the different techniques of measurement through ADCP current meter, they can record the velocity profile of water currents over a wide range of depths. The instrument sends out sound waves in the water and analyzes the Doppler shift of the reflected waves, which yield an understanding of the current structure from surface to seabed with a great amount of detail.

4. How do ADCPs using the Doppler principle work?

Acoustic Doppler Current Profiler (ADCP) work on the principle of the Doppler. They emit acoustic pulses, or in other words, sound waves into the water. It is these sound waves that scatter against particles in the water-sediment, plankton, and all other small particles. As the sound waves are reflected back to the ADCP after bouncing off the particles, their frequency changes due to the Doppler effect.

If the particles are moving towards the ADCP current profiler, the reflected wave frequency is higher than the original frequency emitted. In contrast, if the particles are moving away from the ADCP, the frequency of the reflected wave would be lower. Based on this principle, there is great precision in the measurement of frequency shift by the ADCP flow meter in order to get the velocity of the particles. Because the particles move along with the water current, the estimated velocity of the particles is a measure of the water current velocity. One ADCP profiler can transmit sound pulses in multiple directions; hence, it can measure current velocity not only in three-dimensional space but also at various depths, providing, therefore, a comprehensive profile of the current structure.

5. What's needed for high - quality measurement of Penang coastal currents?

The measuring equipment for the coastal currents at Penang needs to possess reliable materials for high-quality measurement. Since it would be put in a harsh marine environment, salts of water cause corrosion, and waves or floating debris might exert physical impacts, a casing should be durable. It has to be of an appropriate size and weight. A device of small size is easier to deploy, in particular in areas where access is difficult, such as in small boats or in shallow coastal waters. A light device is easier to handle and install.

Low power consumption is of great importance in view of possible long-term measurements. Cost-effectiveness is also important in view of the large numbers of measurements that often need to be carried out. In the case of ADCPs, for the casing, a titanium alloy is preferred. It resists corrosion well, which is helpful in the marine environment of Penang. The saltwater will have very minimal corrosive effects on it in the long run. It is strong and has a very high strength-to-weight ratio; thus, strong yet lightweight structure can be made to protect the internal components of the ADCP meter.

6. How to Choose the right equipment for current measurement?

The first consideration in the selection of the appropriate equipment for current measurement in Penang should be the usage. A ship-borne ADCP shall be appropriate for measurements from a moving vessel. It can display real-time current data while the ship is moving, hence helping one understand how the water may be flowing at different locations. A bottom-mounted ADCP will be good for measurement at a fixed location near the seabed and can carry on continuous monitoring of the current at one point with consistent data in time. For those measurements which have to cover a wide area and are not bound to any specific depth, a buoy-type ADCP is appropriate.

From the point of view of frequency selection, a depth up to 70m can employ a 600kHz ADCP. For water depths between 70m and 110m, a 300kHz ADCP is much more suitable. For very deep waters, however, of up to 1000m, a 75kHz ADCP has been recommended.

There are well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is also worth considering. It is made of all - titanium alloy material and offers a great cost - performance ratio. You can find more information about it on the website: https://china-sonar.com/.

Here is a table with some well known ADCP instrument brands and moels.