How can we measure the coastal currents of Rizhao?

1. Where is Rizhao?

Rizhao is a coastal city in Shandong Province, China. It lies on the southern coast of the Shandong Peninsula, facing the Yellow Sea. The city is endowed with a wonderful coastal landscape comprising long sandy beaches, clear blue waters, and a pleasant climate.

Rizhao has a warm-temperate monsoon climate. The summer is warm and humid, with abundant sunshine and rain; winter is rather mild. So, Rizhao also provides suitable conditions for the growth of various plants. The Rizhao landscape is divided by coastal dunes, wetlands, and rocky shores.

Highly valued is Rizhao for its cultural wealth: its fishing culture, deeply rooted among its citizens since it has been an very relevant industry since time immemorial. It reflects on the architecture, where life has much to do with the sea.

Rizhao determines its identity in large part with the Yellow Sea that lies next to it. The topography of the seabed off the coast of Rizhao allows for shallow areas close to the shore to become deeper as further away from the shores. Generally speaking, the waters are dominated by a number of factors: tides, winds, and oceanic currents from the larger Yellow Sea area.

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

Several factors explain the behavior of coastal currents around Rizhao. The first important reason is the monsoon climate. In summer, the southeast monsoon may push the surface waters, thereby determining the direction and strength of the coastal currents. Winds push the water to create a particular pattern of current, favorable for activities like sailing and fishing. This is quite different in winter when the northwest monsoon takes over and often differs in both directions of currents and their speeds.

Topography of the bottom surface plays an important factor. Underwater ridges, troughs, and shoals can all serve to divert the water in one direction or another and even affect the speed at which the water moves. In shallow regions, the current is much slower, while deeper regions can have stronger and more complex flows. For example, near the shoals, the water goes down in speed, due to their relatively shallow depth, while in troughs the water may be very vigorous.

Another important aspect involves tides. The Yellow Sea experiences continuous tide rises and falls, with strong tidal currents. Tidal currents are very strong, especially in the regions of estuaries and narrow inlets. These currents are very important in the transportation of sediments, nutrients, and marine organisms. They also influence coastal erosion and deposition processes, hence affecting the shape of the coastline and life distribution along coasts.

Besides this, the interaction of this with the larger-scale ocean currents originating from the Yellow Sea and other adjacent regions may eventually modify the coastal currents near Rizhao. These oceanic currents can bring in water masses with different temperatures and salinities, further influencing local current dynamics. For instance, the intrusion of warmer or colder water masses changes the temperature inside the coastal waters and thus affects the local marine ecosystem.

3 How to Observe the Coastal Water Flow of Rizhao?

Accurate measurement of the coastal currents in Rizhao is highly useful for various purposes, such as marine safety, fishery management, and coastal protection. Traditional observation of coastal water flow relying on buoys and current meters has been practiced for a rather long period of time. These are limited in terms of their accuracy and coverage.

Acoustic Doppler Current Profilers have now become the more sophisticated and handy means of measurement of coastal currents. They use the Doppler principles to measure the velocity of water flow.

3.1 How do the Acoustic Doppler Current Profiler(ADCP) using the principle of Doppler work?

ADCP current meter emit sound waves into the water. These sound waves interact with moving particles in the water, such as suspended sediments and small organisms. Due to the movement of the particles, the frequency of the reflected sound waves changes. This frequency shift is related to the velocity of the current.

The transducer array emits and receives the sound waves in different directions. According to the frequency shift of reflected waves in all directions, it can calculate the speed and direction of the current at different depth if analyzing the frequency shifts of the reflected waves. The three -dimensional comprehension of the current structure will be obtained. 

3.2 What's required for the high-quality measurement of Rizhao coastal currents?

To carry out the measurement of coastal currents in Rizhao, several factors have to be put into consideration. Equipment reliability is the paramount factor. The ADCP current profiler should be made of a material that can resist the harsh marine environment.

Titanium alloy is the best casing material for ADCP doppler. It is highly resistance to corrosion, which is very paramount in the salt-water environment of the coast. These also resist the corrosive action of seawater and marine organisms, which provides long performance for the equipment. Besides toughness, it is light. The strength will enable the alloy to sustain physical stresses present within the marine environment, while light weight facilitates handling and installation.

In addition to the material reliability of the equipment, small size, light weight, low power consumption, and low cost are also welcomed. The compact and lightweight ADCP flow meterwill be easier to carry and launch, while most locations are accessible to make measurements. Its low power consumption enables longer operations without needing frequent battery replacement or a major power supply. It allows the deployment of larger numbers in a cost-effective manner that would permit widespread monitoring of the coastal area.

3.3 How to choose the right equipment for current measurement?

The choice of the right equipment for measurement of the coastal currents in Rizhao will depend on a number of factors. The intended application of the equipment is one of the important criteria.

If, on the other hand, the measurements are to be made from a moving vessel, then a ship-mounted ADCP meter would be appropriate. In this case, real-time data on the current could be obtained as the vessel moved along the coast, providing a continuous record of the current condition.

The alternative is the bottom-mounted ADCP profiler, if the measurement has to be at a fixed location on the seabed. It can be installed at a point and can yield a long-term stable measurement of the current at that location.

An ADCP buoy-mounted setup is an alternative for applications in open water or in those locations where a fixed installation is impracticable. This device will be able to measure the current over a larger area and transmit data wirelessly.

The selection of the frequency is based on the water depth. For water depths up to 70 meters, a general application of a 600 kHz ADCP will work. In the event of water depths within the 70-110 meters range, a better option would be an ADCP of 300 kHz. For deeper waters with a limit of 1000 meters, one should consider using 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 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.