How can we measure the coastal currents of  Maoming?

1. Where is Maoming?

Maoming is a burgeoning city in southern China in Guangdong Province. It boasts a unique geographical position and rich cultural background.

Located in southwest Guangdong facing the South China Sea, Maoming boasts beautiful sceneries. With fine sandy beaches and a brilliant blue sea, its long beaches are inviting. Its tropical and subtropical climates make it a desirable place to live and visit.

Maoming also possesses several natural resources, particularly petroleum and natural gas. Its petrochemical industry has contributed much to its economic development.

The adjacent waters of Maoming include the Beibu Gulf. The Beibu Gulf is an important marine area that has abundant fishery resources and diversified marine ecosystems. The clear waters and warm currents of the gulf create a suitable habitat for several species of marine life.

It is ethnically unique in the aspects of human geography, as it houses various local cultures and traditions. People of Maoming are simple, hospitable, and fond of sea activities. Its fresh seafood dishes combined with local food items are also well-known throughout the area.

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

The ocean currents near Maoming are influenced by many components that interactively develop a very intricate marine environment.

Thus, the monsoon predominantly controls the coastal currents. The winds blowing from almost different directions round the year change the direction and strength of the currents. During the southwest monsoon, for example, the wind blows from the southwest and pushes the surface waters north-eastwards. However, during the northeast monsoon, it blows from the northeast and the superficial waters flow southwest.

The other factor is the seabed topography. Depending on the shape of the bottom feature of the sea floor, the depth defies the flow of the currents. The Maoming seabed is generally flat but contains a few areas with deep trenches that hamper the current speed and direction of flow.

Of course, another important factor contributing to the formation of the coastal currents is the tides. With the rise and fall of the tides, the water level changes to give birth to tidal current flows that might affect the water flow along the shores. Besides, the interaction of the tides with the monsoon winds may further complicate the current patterns.

The nature of the coastal currents can also be determined by changes in temperature or salinity. Temperature and salinity are integral variables of the density of water, hence influencing the nature of the flow of currents. Offshore of Maoming, the warmth from the South China Sea and the upwelling coolers from Beibu Gulf may create density gradients that could determine the course and strength of the currents.

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

Maoming coastal currents can be observed through many means. Traditionally, methods used to measure the speed and direction of currents include drift bottles, current meters, and satellite imagery. However, each of these methods has its own limit in terms of accuracy and spatial coverage.

Because of their post-improved methodology, ADCP have been increasingly becoming popular in the last decade for the measurement of coastal currents. Acoustic doppler flow meter use the Doppler principle to measure the velocity of water flow at several simultaneous layers of the water column. Thus, this gives a more detailed and actual scenario of the currents.

3.1 How do ADCP using the Doppler principle work?

Acoustic Doppler Current Profiler(ADCP) transmit sound waves into the water, which then measures the frequency shift in waves reflected back. The frequency shift will be because of the movement of the water particles, which are directly related to the velocity of flow of water. By analyzing the shift in frequency, the ADCP can estimate the water flow velocity in various directions.

Typically, an ADCP current meteris a suite of a number of transducers that emit and receive signals in the form of sound waves. The transducer suite is usually mounted on a ship, a mooring, or a buoy. As the signal travels through the water, the reflected signal by the particles of water bounces back and reaches the transducer suite again. After receiving, computers process the signal to calculate the velocity of the flow of water.

3.2 What is required for the high-quality measurement of the Maoming coastal currents?

In measuring the coastal currents of Maoming, several factors need to be considered. First, the equipment has to be reliable. The ADCP current profiler, to measure the current, must be made from durable materials that can withstand the harsh marine environment.

The advantages for ADCP doppler casing requirement point to this material, titanium alloy. Especially, it is more anti-corrosive with saltwater and other marine elements. It is strong, lightweight, and easy to handle and install. Additionally, since the coefficient of thermal expansion of the material is low, it also helps ensure accurate measurement from extreme temperature conditions.

Besides material reliability, other factors to be considered include size, weight, power consumption, and cost. Small-sized and lightweight ADCP flow meter, for big-scale measurements, allow their easy deployment and retrieval. Low power consumption is also important in order to allow longer battery life and reduce the frequency of recharging. Besides, cost determines large-scale feasibility.

3.3 How to Choose the right equipment for current measurement?

For choosing the right equipment for Maoming's current measurements, there are many factors to select: what the equipment must be used for since different applications will need different types of ADCP meter. For example, ship-mounted ADCP are suitable for current measurement where the ship is in motion, while bottom-mounted ADCP can be used for long-term current monitoring where it needs to maintain the same position. Buoy-mounted ADCP can be installed in areas where other methods of deployment may not work efficiently for the measurement of currents.

The other important consideration will be the frequency of an ADCP profiler. Different frequencies suit different water depths. For example, a 600 kHz ADCP will be appropriate for shallow water than 70 meters. A 300 kHz ADCP will be appropriate for water shallower than 110 meters. A 75 kHz ADCP shall be suitable in deeper waters as high as 1000 meters.

Some ADCP brands include Teledyne RDI, Nortek, Sontek, and China Sonar. Among them, the brand China Sonar owns its relatively high-quality PandaADCP at an average price. The PandaADCP is made of titanium alloy material. Therefore, high quality and corrosion resistance can be guaranteed. Various frequency options could be chosen from, which can make it suitable for different depth water areas. For more details, please refer to: https://china-sonar.com/.

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