How to measure coastal currents of Fuding?

1. Where is Fuding?

Fuding is a coastal city in Fujian Province, China. It is in the northeastern part of Fujian and fronting the East China Sea. The city is endowed with beautiful natural scenery that combines mountains and the sea.

The subtropical maritime climate of Fuding makes it have mild winters and warm summers, with a plentiful amount of rainfall received throughout the year. This is the reason why the area can be fully equipped with various species of flora and fauna, enriching the local ecological scenery. Dominated by seas, sandy beaches, rocky shores, and other coastal features are occupied by small islands.

There is also a unique cultural aspect about Fuding. Rich cultural heritage of the locality comes as a result of traditional festivals, handicrafts, and local cuisine. Aquaculture and fisheries in the city are among the vital sectors of the local economy since the neighboring East China Sea is always filled with marine resources.

The waters around it originate from the East China Sea. In general, shallow waters can be found over the continental shelves that lie relatively close to shore, while deeper ones are further out. This would, among other factors, affect the circulation of waters with the distribution of marine life. Several bays and inlets create places of shelter for boats and have their significance for local fishermen.

2. Fuding - What is the condition of the coastal currents?

Many reasons account for such a variety of coastal currents around Fuding. The most prominent among them is, of course, the monsoon climate. During summer, the general direction of the southeast monsoon brings warm and moist air; this may influence the direction and strength of the coastal currents. Of course, the wind contributes to pushing the surface water in such a way that results in a particular pattern of currents. In winter, the northwest monsoon changes the situation, often resulting in the opposite current directions and speeds.

Another critical factor is underwater topography. Variations in the directions and speeds of current are often related to the ridges, shoals, and troughs of the ocean bottom. For example, the current may be slower through shallow seabeds, whereas it can speed up into deeper channels or troughs.

The tides are also important. The periodic outfall and inflow of the tides in the East China Sea result in tidal currents. These are substantial by estuaries and narrow passages. They are vital in the transportation of nutrients and sediments, which essentially impact the growth and dissemination of marine organisms, hence coastal geology.

Besides, the interaction with the larger-scale ocean currents from the Taiwan Strait and other regions can also influence the coastal currents near Fuding. These oceanic currents may bring water masses with different temperatures and salinities, further modifying the local current dynamics.

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

The exact measure of the coastal currents at Fuding becomes very important for many aspects: marine safety, fishery management, and environmental protection. Traditional means for the observation of the flow of water through the areas of a coast had long relied on buoys and current meters. The latter has certain limits to precision and coverage.

Acoustic Doppler Current Profilers have become more refined and accessible tools for measuring coastal currents. The ADCP current meter make use of the Doppler principle to measure the water flow velocity.

3.1 How do the ADCPs Using the Doppler Principle Work?

Acoustic Doppler Current Profiler(ADCP) send out sound waves into the water. Particles in the water, which are suspended sediments and small organisms, will interact with the sound waves emitted. It is during these interactions that the particles will experience changes in the frequency of the returning sound waves due to the speed of the current.

Its transducer array sends and receives sound waves in different directions. By measuring the change in frequency of the return waves in different directions, the ADCP current profiler is able to work out the speed and direction of the current at different depth levels. In this way, three-dimensional knowledge of the current profile is achieved. 

3.2 What is required by high-quality measurement of the Fuding coastal currents?

For good measurement of the currents in the Fuding coastal region, a number of factors should be ensured. First, one must ensure that the equipment is of the desired quality. For an ADCP doppler, the material used for the case must withstand the harsh conditions at sea.

An ideal cases' material in ADCP flow meter is that of Titanium alloy. The cases have been found to resist corrosion to a greater scale, which is very important when at the salty water on the coast. It resists the effects of seawater corrosion and those from marine organisms so that this equipment can last as long as possible. Besides, this alloy is very strong yet lightweight. The strength gives it sufficient capacity to bear the physical stresses in the sea environment, while at the same time, it is light, hence fairly easy to maneuver and repair.

Besides material reliability, other features such as small size, low weight, low power consumption, and low cost are welcome. A compact and lightweight ADCP meter is easier to carry and deploy, therefore being able to measure the flow in more locations. Low power consumption enables longer operation without the frequency of battery replacement or a large power supply. Hence, it is cost-effective for large-scale deployment to allow much thorough monitoring of the coastal area effectively.

3.3 How to Choose the right equipment for current measurement?

To choose the appropriate equipment for measuring the currents in the coast of Fuding, there is a number of factors to be considered: among which, the intended application of the equipment is critical:.

With moving vessel measurements, a ship-mounted ADCP would be an appropriate fit. It can thus provide real-time current data when the vessel is moving along the coast for continuous monitoring of current conditions.

In cases where measurement must be done at a specific location on the seabed, a bottom-mounted ADCP profiler will be appropriate. It therefore would serve best if it is installed at one point and measures the current over a long period at that point stably.

It can be buoy mounted for applications in open water or in situations where an installation at a fixed place is not possible. An example of this would be current measurements over a larger area with wireless transmission.

Another factor that relates to the frequency choice is that various depths of water cut across various frequencies. For example, a depth of up to 70 meters of water uses a 600 kHz ADCP. However, areas whose bottoms lie between 70 and 110 meters should be mapped using a 300 kHz ADCP. For waters with a depth of up to 1000 meters, one should go for 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.