How to measure the coastal currents of Tawau?

1. Where is Tawau located?

Tawau is a coastal city found in the southeastern part of Sabah, Malaysia. It is a lively and diverse place that faces the shores of Celebes Sea.

The city is bordered by a mix of tropical rainforest and coastal landscape. A wide variety of animals, including species of monkeys, birds, and rare flora, can be found housed within the rainforests. Tawau is also famous for its agricultural activity in the form of widespread palm oil plantations around it.

The local community is one rich in several ethnic groupings, with the Chinese, Malays, and indigenous peoples making up the bunch. These cultures and traditions mixed together to give way to a distinctive local identity. There are some beautiful sandy beaches along the coastline of Tawau, with clear blue waters. There are also extensive mangrove forests, which are highly ecologically important. These mangrove forests serve as a natural barrier that protects erosion in the coast and forms a breeding ground and nursery for several marine species. These shallow coastal waters are highly productive, with rich nutrients supporting a complex community of shellfish, small fish, and other invertebrates.

The Celebes Sea is the neighboring extensive body of water with variances in seabed topography, but with sandy regions, coral reefs, and slopes beneath the waterline. The higher elements of the sea are allowed to be used for fishing and shipping, with the shallower areas along coasts playing an important role in nature, such as local fishing and recreational activities.

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

Several conditions make variations to the coastal currents off Tawau. By large, this involves the monsoon winds. In periods of the southwest monsoon, the surface waters are driven by the prevailing winds into one direction. This may provide a transport of warm and nutrient-rich waters, relevant for the proliferation and distribution of marine organisms. In the event of the northeast monsoon, the pattern of the current changes, with cooler waters brought in from elsewhere.

Another very important influence is the topography of the seabed. The topography includes undersea coral reefs, ridges, and troughs that could potentially defe, accelerate or decelerate the currents. For example, the flow of water around a coral reef may be deflected and results in some areas of upwelling and downwelling. These are important for the nutrient cycle in bringing deeper, nutrient-dense waters upward towards the surface and promoting phytoplankton growth and other primary producers.

Another very important input ingredient of input is freshwater from local rivers and streams. The discharge of freshwater is capable of varying the salinity in the respective coastal waters. Because of differences in density, in general, the layering of different types of water may be developed along with influencing the currents' vertical movements.

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

Surface Drifting Buoy Method: Buoys are deployed on the water surface and allowed to drift with currents. Their movements are followed through satellite-based tracking systems. From the path that the buoys trace, one can get information about the direction and speed of the surface currents. This method principally deals with the surface layer, though, and thus cannot yield much about the currents across the whole water column.

Anchored Ship Method: A ship is moored in the water off the coast and from which current-measuring instruments are lowered into the water at a number of levels to measure the characteristics of the current at different levels. But the presence of the ship can interfere with the natural movement of the water and is not efficient for long-term continuous measurements.

Acoustic Doppler Current Profiler (ADCP) Method: ADCP represents a more sophisticated and convenient measurement method of the coastal currents. It can give a detailed profile of the current velocities right from the surface to a considerable depth, giving almost a complete picture of the flow patterns within the water column.

4. How do ADCPs using the Doppler principle work?

An ADCP current meter works on the basis of the phenomenon known as the Doppler effect. They send acoustic signals into the water. These acoustic pulses interact with the moving particles in the water, such as sediment particles and small organisms. Because the water is in motion, the frequency of the reflected pulses changes due to the Doppler effect. The ADCP measures this frequency shift and calculates the velocity of the water at different depths. The instrument has several transducers that can project and receive acoustic signals along different axes, hence can measure the current three-dimensional velocity structure of the water column.

5. What does high quality measurement of Tawau coastal currents require?

Generally speaking, the equipment for the measurement of currents in a coastal area, especially near Tawau, should be made with material that can be well relied upon. It has to resist chemical action-seawater and the mechanical forces from waves and currents. It must have a compact size with lightweight, due to the fact that it should be much easier to launch in the water-either at the bottom, from a buoy, or on a boat.

The power consumption should be low, especially for long-term measurements in remote locations. This system should be effective but not necessarily costly. Large-scale measurement requires that the equipment is relatively cheap. The casing of the ADCP current profiler is preferably made of Titanium alloy. Because of the marine environment, resistance to corrosion is quite important, like that of Titanium alloy. It is also strong, tough, and durable to resist sea conditions and at the same time light in mass.

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

Usage scenarios need to be considered when equipment for current measurement near Tawau is chosen. If the measurements are ship-based, then an ADCP mounted on a ship would suffice. It can be installed on the hull of a ship and measure the currents while the ship is in sail or stationary condition.

In a measurement of currents near the seabed, an ADCP flow meter sitting on the bottom is quite appropriate. It can be easily placed at the bottom and measure the currents close to it quite accurately.

An ADCP mounted on a buoy is quite suitable for floating applications. It can be attached to a buoy for measuring currents at different depths when the buoy floats.

ADCP Frequency: A 600kHz ADCP will normally suffice for water depths up to 70m, while a 300kHz ADCP is better for water depths up to 110m. For even deeper waters of up to 1000m, a 75kHz ADCP will suffice with good measurement results.

There are several well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, a highly recommended Chinese ADCP brand is China Sonar PandaADCP. It is made of all - titanium alloy material, ensuring excellent performance and durability in the marine environment. It also offers an outstanding cost - performance ratio. You can find more information on its website: https://china-sonar.com/.

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