How do we go about measuring the coastal currents of Fuzhou?

1. Where is Fuzhou?

Located in Fujian Province, China, Fuzhou is an energetic city located on the southeastern coast. It is a place where historical charm meets modern development.

Geographically, Fuzhou borders the Taiwan Strait in the east. The coastline is made up of sandy beaches, muddy flats, and rocky outcrops. Climatically, Fuzhou has a subtropical monsoon climate with warmth and humidity throughout the year. The rich rainfall and mild winter provide various vegetations, such as subtropical forests to coastal mangroves.

Fuzhou is the city with profound historical and cultural background. It has an illustrious history as an oceanic port city and holds an important place in trade and culture exchange. Local architecture features a mix of ancient pagodas, temples, and traditional Fujian-style houses that reflect different ages in history. People in Fuzhou have very rich cultural traditions: peculiar dialects, traditional operas, and handicrafts.

Located next to Fuzhou is the Taiwan Strait, which has been a very important shipping lane and source of marine products. Many species of fish and shellfish live in the waters of the strait. The tidal action in the area plays a very important role both in the local ecosystem and economy, thus greatly affecting fishing and salt-making activities in the region.

2. What is the condition of the coastal currents around Fuzhou?

A variety of factors, including the prevailing monsoon winds, influence the coastal currents around Fuzhou. During summer, the southeast monsoon brings warm and humid air, capable of pushing surface waters and thus changing the direction and strength of currents along coasts. In winter, the northwest monsoon becomes stronger and shifts the patterns of currents.

Topography of the ocean floor influences the directions and characteristics of the coastal currents. The underwater ridges, valleys, and shoals can easily produce water flow in various directions at variable speeds. Shallower areas may have more reduced currents, while deeper troughs lead to stronger, more complex flow.

Another critical factor is tides. Because of the regular tide ebb and flow, in most time it can form heavy tidal currents in Taiwan Strait. Remarkably, strong tidal currents formed near estuary and narrow channel. It forms a very important vehicle in sediment transportation and nutrient and marine organism distribution for coastal geology and marine ecosystem health.

Besides, the interaction with larger-scale ocean currents from the South China Sea and the East China Sea is able to modify coastal currents near Fuzhou further. These oceanic currents are capable of introducing water masses with different temperatures and salinity, and further influencing local current dynamics.

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

The coastline currents of Fuzhou are of great importance and have to be measured as accurately as possible for various applications, ranging from marine safety and resource management to scientific research. The traditional methods include those based on buoy, drifter, and current meter conventions that have been in use for a long time. These methods have some disadvantages with regard to accuracy and coverage.

While these systems have become relatively common, ADCP current meter represent a more sophisticated and convenient means of measuring coastal currents. Acoustic doppler velocity meter can resolve the velocity and direction of the current with a good resolution at different depth intervals.

3.1 Principle of operation of Doppler principle ADCPs

Acoustic Doppler Current Profiler(ADCP) operate on the basis of the Doppler principle. They shoot a given frequency sound waves into the water. These sound waves interact with moving sediment or small organisms in the water, thus returning with a changed frequency. This change in frequency is linearly proportional to the velocity of these particles and, thus, the water current velocity.

From this frequency shift, the reflected sound waves calculate the speed and direction of the current at each depth inside the flow profile. The transducer array in an ADCP current profiler emits and receives sound waves in multiple directions, allowing for a three - dimensional measurement of the current.

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

Several factors have to be considered for the high-quality measurement of coastal currents in Fuzhou. First and foremost, the equipment reliability has to be considered. The ADCP doppler should be constructed from materials which will survive the harsh condition of the sea.

Amongst the best materials found for making the casing of an ADCP flow meter is a titanium alloy. It has several added advantages. It is first extremely resistant to corrosion, a vital factor in the salty water conditions of the coast. The material can well resist corrosive actions of sea water and marine organisms, hence enabling the equipment to function for years. Secondly, the titanium alloy is of great strength but light in weight. With such strength, it is able to resist physical stresses in the marine environment, while with light weight the equipment will be easier to handle and install, especially when it has to be deployed in difficult locations.

Besides material quality, other properties of small size, low weight, and low power consumption and cost are also advantageous. A compact and lightweight ADCP meter is easy to transport and deploy at measurement sites. Low power consumption allows longer operation without frequent battery replacement or a large power supply. Cost-effectiveness is an important factor in large-scale deployment and allows for more comprehensive monitoring of the coastal area.

3.3 How to Choose the right equipment for current measurement?

There are several factors in choosing appropriate equipment for measurement of the coastal currents in Fuzhou. Use of the equipment comes first.

With that in mind, the ADCP mounted on a ship would be quite suitable for measurements from a moving vessel. It provides real-time current data as the ship travels along the coast and therefore enables one to continuously assess the prevailing current conditions.

If one wants to conduct a measurement of current from the sea bottom at a fixed location, a bottom-mounted ADCP profiler is done. It could be installed at any point with the ability to give stable long-period measurements of currents for that location.

An ADCP on a buoy would be useful in those applications where an installation in open water or a fixed installation is impossible. It can measure over a larger area and transmit the data wirelessly.

As far as the selection of frequency is concerned, different frequencies apply for different water depths. For water depths up to 70 meters, a 600 kHz ADCP would generally suffice. For waters with a depth of between 70 and 110 meters, one should prefer a 300 kHz ADCP. In the case of deeper waters, up to 1000 meters, one should consider an ADCP operating at 75 kHz.

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.