How can we measure the coastal currents of Quanzhou?

1. Where is Quanzhou?

Quanzhou is an amazing coastal city found in Fujian Province, China. It is situated along the southeastern coast, and strategic position that has been very important in history and commerce.

Geographically, Quanzhou faces the Taiwan Strait on its east side. The coastline stretches mile after mile in diversity, comprising beaches with sand, rocky coasts, and bays that are sheltered. Its climate is subtropical in condition and maritime in nature, marked by mild winters and warm summers. The rich sunlight and abundant rainfall put life into a well-developed ecosystem, with varieties of plants and animals thriving.

Quanzhou is the city of rich history and culture. It once was a major port in ancient China, and a starting point of the Maritime Silk Road. The architecture in the city reflects its glorious past-ancient temples, pagodas, and traditional houses. The local people have a strong sense of cultural identity and are known for their craftsmanship in porcelain and handicrafts.

The adjacent waters of Quanzhou are very important. The Taiwan Strait is a main navigation route and a rich fishing ground, with many kinds of fish, shellfish, and other sea organisms. It also links Quanzhou with other regions and countries, which helps to develop the trade and cultural exchange.

2. What is the current situation of the coastal currents near Quanzhou?

Several factors account for the coherence of coastal currents around Quanzhou. The great influence is exerted by the monsoon winds: during summer, southeast monsoon brings warm and moist air, whereas during winter, the northwest monsoon is dominant and changes the direction and velocity pattern of the coastal current.

Reliefs of the bottom topography affect coastal currents, too. These would be in the form of ridges, valleys, and shoals that underwater make water sometimes flow in various directions and with different speeds. For example, regions with relatively shallow seabeds will have slower currents whereas those with deeper troughs would have stronger and complex flows.

Besides, tides also play an essential role. The Taiwan Strait periodic tidal flow would probably induce major fluctuations of the coastal current. In some area, especially around estuaries and narrow channels, the tidal current can be very strong. And this kind of regular tidal current also would contribute to the sediment transports and nutrients, which directly influences the marine ecosystem and coastal geology.

In addition, the interaction with the more large-scale ocean currents from the South China Sea and the East China Sea also changes the coastal currents along Quanzhou. Such oceanic currents could bring in water masses of different temperatures and salinities, influencing further local current dynamics.

3. How to Observe the Coastal Water Flow of Quanzhou?

Precision in measuring the coastal currents at Quanzhou Bay becomes indispensable for different uses related to marine safety, resources management, and scientific research. Until now, buoys, drifters, and current meters have conventionally been used observation methods for water flow. However, these methods have poor accuracy and limited coverage.

Acoustic Doppler Current Profilers are an increasingly sophisticated and much more convenient means of measuring currents on the coast. acoustic doppler flow meter can give high-resolution measurements of current velocity and direction with depth.

3.1 How do Doppler Principle ADCP work?

Acoustic Doppler Current Profiler(ADCP) are based on the principle of the Doppler effect. They transmit sound waves of a known frequency into the water. As these waves encounter and return from moving particles in the water, like sediment or even small organisms, the frequency of the reflected waves changes. This frequency shift is directly proportional to the velocity of the particles and, therefore, to the velocity of the water current.

Since the frequency shift of the reflected sound waves is measured, an ADCP current meter can calculate current velocity and direction for multiple depths. An ADCP current profiler has its transducer array emitting and receiving in multiple orientations so as to provide a three-dimensional measurement of the current.

3.2 What's needed for high-quality measurement of Quanzhou coastal currents?

Several factors have to be put into consideration to realize a high - quality measurement of the coastal currents in Quanzhou. Equipment reliability is among the most paramount aspects. The ADCP doppler is recommended to be built using materials that can withstand the harsh marine environment.

Titanium alloy is among the best options for casing ADCP flow meter. Several advantageous features are offered by it. First, it has excellent resistance to corrosion, which is critical in the saline-water-type of environment at the coast. It resists the corrosive action of seawater and the organisms found in seawater for continuously sustainable equipment performance. Second, the alloy of titanium is as strong but lightweight. This strength imparts resistance to the physical stresses encountered in the marine environment, while its light weight makes it easy to handle and deploy, especially when the equipment has to be deployed in access conditions.

Besides the quality of the material, the small size and weight, low power consumption, and low cost provide an additional advantage. Being compact and lightweight, an ADCP meter is much easier to carry and deploy, hence the measurement of currents in various locations can be afforded. The low power consumption allows the instrument to run longer without the requirement for more frequent battery replacement or a large power supply. Cost-effectiveness is crucial for being able to have wide-scale deployment to get fuller coverage of monitoring of the coastal area.

3.3 How to choose the right equipment for current measurement?

There are several factors to consider when selecting appropriate equipment to measure the currents in the coast of Quanzhou. First to be considered is the intended use for which the equipment shall be used.

One option to do the measurement from a moving vessel is an ADCP mounted on the ship. It would be able to provide a real-time current profile while the ship travels along a coast, offering the ability for continuous assessments of the current conditions.

In case the measurement is required at a fixed location on the seabed, a bottom-mounted ADCP should be used. It can be installed at that point, at which it does its job of recording long-term stable measurements of the current at that point.

An ADCP profiler on a buoy can be used in open water or where a fixed installation is not practical. It is able to measure current over a wider area and transmit the data wirelessly.

These are best fitted for different water depths, just like the choice of frequency. A 600 kHz ADCP would be generally appropriate for starting water depths up to 70 meters. From 70 to 110 meters, one could consider using a 300 kHz ADCP. For deeper waters with a depth up to 1000 meters, one should consider a 75 kHz ADCP.

When it comes to choosing an ADCP brand, well - known international brands such as Teledyne RDI, Nortek, and Sontek are popular options. However, for those seeking a cost - effective yet high - quality alternative, the China Sonar PandaADCP is worth considering. Made entirely of titanium alloy, it combines durability and reliability with an excellent price - performance ratio. You can find more information about it at https://china-sonar.com.

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