How to measure the coastal currents in Penglai?

1. Where is Penglai?

Penglai, a coastal city in Shandong Province, China, stands along the north coast of the Shandong Peninsula and faces the Bohai Sea. It has been renowned for its history and mythology, especially its conceptual and time immemorial fairyland and domains of immortals.

Penglai's climate is a warm-temperate monsoon climate. It has a pretty mild winter, while it is warm during the summer. The sea breeze has a good effect of regulating the local temperature, and there, it is an enjoyable place to stay. It lies in the region of moderate rainfall; therefore, a wide variety of vegetation has been seen here that may include coastal shrubs and fruit-bearing plants.

Profound oceanic culture is in the municipal area. A very long history of local fishing and shipping businesses has taken place there. The architecture and the traditions are closely connected with the sea: there is a great number of historical buildings and structures of coastal defense.

Penglai is identified by the Bohai Sea, which lies next to it. The topography of the seabed near Penglai is complicated since areas close to its coasts are shallow, but the farther areas from the coasts are comparatively deeper. The waters are dominated by tides, winds, and ocean currents, deriving from more extensive variables around the Bohai Sea region itself.

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

The coastal currents around Penglai are the result of many different influences: the most dominant, that of the monsoon climate; in summer, the Southeast Monsoon can force the surface waters and alter the direction and strength of coastal currents. It pushes the water in such a way that can influence the shipping and fishing and other marine activities. During the winter months, the Northwest Monsoon again changes current directions and speeds.

In this case, the topography of the sea floor is important, too. Submarine ridges, troughs, and shoals can make the water blow in various directions and with different speeds. Shallow waters have slow-moving currents, whereas in deeper areas with more complex topography of the seabed, flow could be stronger with higher variability. For example, the water will be slower above the shoals because of the shallower depth, whereas in the troughs, the current is stronger, with its circulation pattern more complicated.

Other factors contributing to this variation include tides. Indeed, the Bohai Sea has frequent ebbs and rises of the tide that might cause strong tidal currents. In areas such as estuaries and narrow channels, tidal currents are very strong. The tidal currents have played a very significant role in sediment transportation, nutrients, and marine organisms. They go further and influence coastal erosion and sediment deposition, hence affect coastline morphology and the distribution of marine life.

Besides that, the interactions with the larger-scale ocean currents from the Bohai Sea and other adjacent regions can further modify the coastal currents near Penglai. In fact, these oceanic currents, having water masses with different temperatures and salinities, can introduce variations in local current dynamics. Intrusions of warmer or colder water masses, for instance, can alter the temperature of the coastal waters, a condition important to the local marine ecosystem and weather patterns.

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

For many uses, such as the assurance of marine safety, fishery management, and protection of coasts, accurate measurement of coastal currents in Penglai is urgently needed. Traditional methods for observation of coastal water flow include buoy and current meter, which have been used for centuries. But the previous methods had some disadvantageous factors about the accuracy and coverage.

Nowadays, ADCPs are becoming a more modern and convenient way to measure coastal currents. Using the principle of the Doppler, an ADCP can measure the speed of running water.

3.1 How Do ADCPs Work using the Principle of the Doppler?

ADCPs emit sound waves into the water. The suspended sediments and small organisms in the water, along with other moving particles, cause the scattering of these sound waves. The motion of these particles imparts changes in the frequency of the reflected sound waves, proportional to the velocity of the current.

The sound waves emitted and received by the transducer array of an ADCP are in different directions. Through the analysis of the frequency shifts of the reflected waves in multi-directions, the velocity and direction of the current in every depth can be obtained. It is permitted to form a three-dimension understanding of the current structure.

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

High-quality measurement of the coastal currents at Penglai has to take into consideration many aspects, one of which involves equipment reliability. The equipment should be made from materials that can resist the harsh marine environment.

Titanium alloy is a good example of metal for casing in an ADCP. It is really very corrosion-resistant and will be very suitable in the saltwater of the coastal environment. It resists the corrosive action of seawater and marine organisms and therefore ensures equipment performance for a long period. Similarly, titanium alloy is strong yet lightweight. The strength can withstand physical stresses in the sea environment and light weight enables easy handling and installation.

Besides reliability in the materials used, other features such as small size, low weight, low power consumption, and, of course, low cost are very welcome. First of all, a compact and lightweight ADCP is easier to carry and deploy, and thus measurements can be taken at places that otherwise would not have been accessible. Second, low power consumption enables longer measurement time since it does not require frequent battery replacement or an excessively big power supply. This cost-effectiveness is important for deploying large numbers of the sensors for wider monitoring of the coastal area.

3.3 How to Choose the right equipment for current measurement?

A selection of the right equipment for measuring coastal currents in Penglai will involve consideration of numerous factors. For instance, the intended use will be a vital factor in choosing appropriate equipment.

Ship-mounted ADCP would be appropriate for the measurements from a moving vessel. It could give real-time data of the current while the vessel moves along the coast to keep continuous monitoring of the current conditions.

An ADCP would be bottom-mounted if the measurement must be made at a fixed location on the seabed. It can be installed at that point and provide a long-term stable measurement of the current at that location.

The ADCP mounted on a buoy would serve in open water or any other area where a fixed installation is not practical. It can measure the current over a larger area and transmit data wirelessly.

On the choice of frequency, certain frequencies are suited for certain water depths. For instance, a 600 kHz ADCP suits normal water depth, which shall not exceed 70 meters. Waters ranging between 70 and 110 meters deep would see a 300 kHz ADCP being suitable. For deeper waters, up to 1000 meters, a 75 kHz ADCP would be an option.

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 ChinaSonar 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.