How to measure the Coastal Currents of Miyazaki?

1. Where is Miyazaki?

Located on the eastern coast of Kyushu Island, the Japanese city of Miyazaki is blessed with beautiful beaches and a generally pleasant climate. The Pacific Ocean to the east borders the city, which highly affects the local environment and economy in its own way.

This local area has great fame in the tourism industry; as a result, many people go there for beaches, scenery of coasts, and some water sports. The Pacific Ocean near Miyazaki provides a great amount of fishing facilities to the local economy due to the rich availability of marine resources. This ocean contains different species like skipjack tuna, yellowtail, and sardine. Additionally, large beds of seaweed are found here and a great variety of shellfish.

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

The coastal currents near Miyazaki are determined by many different factors. First, there is the Kuroshio Current. This warm ocean current that flows northward along the eastern coast of Japan brings in warm and nutrient-rich water. It affects the temperature of the coastal waters, the distribution of marine life, and the overall current patterns.

Tidal currents also play an important role. There is a certain tidal range at Miyazaki, and the inflow and outflow of water at high and low tides create a very complex current pattern. The shape of the coastline and the underwater topography are important. The presence of bays, headlands, and underwater ridges may cause the currents to change direction and speed. The speed might also increase at areas of headlands while the water will be deflected into bays. Some examples are that the wind, especially seasonal winds, can drive surface currents, for example, the trade winds, and affect mixing among layers of water.

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

Surface Drifting Buoy Method: Surface-drifting buoy can be launched to track the surface current. The buoy's movement is tracked over time using GPS or other tracking systems. However, this method has limitations. It only provides information about the surface current and can be affected by wind and waves. For example, if a strong wind blows the buoy in a different direction from the actual current, it can lead to inaccurate measurements of the current's direction and speed.

Anchor - Boat Method: In this method, the current could be determined by an anchored boat. Instruments lowered from it would measure current at various depths. It allows for further detailed depthwise measurements but with disadvantages as well. It limits an area in which measurement could be performed as the position of the boat is fixed, and cannot represent in full the large coastal area variability of the currents.

ADCP Method: The ADCP current meter method is more advanced and efficient in measuring the coastal currents. ADCPs emit acoustic signals into the water and measure the Doppler shift of the reflected signals to calculate the velocity of water at different depths. This gives a better profile of the current from the surface to the seabed. Because ADCPs are less affected by surface disturbances, they can operate continuously for longer periods and provide a truer picture of the current structure.

4. How do ADCPs using the Doppler principle work?

ADCPs work on the principle of the Doppler effect. They transmit high-frequency acoustic pulses into the water. Whenever these pulses interact with moving water particles, the frequency of the reflected pulses is changed. If the water particles are moving towards the ADCP profiler, the frequency of the reflected signal is higher than that emitted; if they are moving away, it is lower.

The ADCP meter is equipped with multiple transducers that send and receive signals at different angles. By analyzing the Doppler shifts from different directions and at different depths, the device can calculate the three - dimensional velocity of the water. This means it can determine the horizontal and vertical components of the velocity, providing a detailed understanding of the current's structure and behavior.

5. What is required for good quality measurement of Miyazaki coastal currents?

The equipment should be made of reliable materials that will ensure high-quality measurements of the coastal currents around Miyazaki. With a marine environment involving saltwater, possible storm exposure, and the tides and ocean currents influence, the casing should be really hard. The size of the equipment should be small in order to be easily deployed and retrieved, especially in light of the complex coastal landscape with its beaches and bays.

The lightweight design is preferable because this will make the equipment more feasible during installation and maintenance activities. Low power consumption is necessary in long - term and autonomous operation. Cost - effectiveness is important to allow large - scale measurements.

The casing of ADCPs is preferably made of titanium alloy. The titanium alloy is very resistant to corrosion, which is highly essential in withstanding the corrosive effects of sea water. It is also strong enough and durable to bear the pressure of the water at different depths. Its lightweight nature makes it more convenient for various deployment methods.

6. How to Choose the right equipment for current measurement?

The purpose of use should be considered first when choosing equipment for current measurement near Miyazaki. If the measurement is for navigation of a vessel or short-term research, a ship-mounted ADCP flow meter would be suitable. It provides real-time current information during the voyage.

If the measurements are near the seabed for studying sediment transport or benthic ecology, then a bottom-mounted ADCP would be better; it will capture the details of the near-bottom current. On the other hand, for the long-term and wide-area monitoring of coastal current, a buoy-type ADCP current profiler is ideal.

Regarding the frequency of ADCPs, for water depths up to 70m, a 600kHz ADCP is a good choice. For depths up to 110m, a 300kHz ADCP is more appropriate. And for deeper waters that might be found near Miyazaki, such as areas with a depth over 1000m, a 75kHz ADCP is recommended.

There are well - known ADCP current meter brands such as Teledyne RDI, Nortek, and Sontek. However, a Chinese brand, China Sonar PandaADCP, is also worth considering. It is made of all - titanium alloy material and offers an excellent cost - performance ratio. You can find more information on their website: https://china-sonar.com/.

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