How to measure the Coastal Currents of Akita?

1. Where is Akita?

Akita is a city in the Akita Prefecture of the Sea of Japan side of Honshu. It is a coastal city with traditional festivals, beautiful sceneries, and a rich cultural heritage. Its local economy is diverse, with fishing, agriculture, and manufacturing contributing to it.

The Sea of Japan off Akita is a productive marine area, with a host of fish such as cod, herring, and squid, besides extensive seaweed beds. These are beneficial to the local fishing industry, while the port of Akita is also an important transportation hub in shipping goods such as agricultural products and seafood.

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

Many different things work together to influence the coastal currents around Akita. First, there is the Tsushima Current. This is a warm current that branches from the Kuroshio Current, carrying warm water and nutrients that affect the temperature and distribution of marine life.

Tidal currents are another important factor. The Sea of Japan has a rather considerable tidal range; therefore, the tides at ebb and flow cause very complicated current patterns to form. The shape of the coastline and underwater topography play a crucial role. The presence of bays, headlands, and underwater ridges may cause the currents to change direction and speed. Besides, the wind, especially the seasonal wind across the Sea of Japan, may drive surface currents and mix different layers.

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

Surface Drifting Buoy Method: A surface - drifting buoy can be released into the water to observe the surface current. The buoy movement is tracked over time using GPS or other tracking systems. However, this method has limitations in that it only provides information on surface current and is affected by the wind and waves. Using the same example, where a strong wind blew on the buoy in a direction different from the current; this would result in inaccuracy in the measurements taken of the direction and speed of the current.

Anchor - Boat Method: An anchored boat can be used to measure the current. Instruments are lowered from the boat into the water to measure the current at different depths. Although this permits more detailed depth -wise measurements, this technique also has its own drawbacks. The fixed position of the boat restricts the area of measurement and it may not capture the full variability of the currents in a large coastal area.

ADCP Method: The ADCP current meter method is a more advanced and efficient way to measure the coastal currents. The 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 will give a more comprehensive profile of the current from the surface to the seabed. ADCPs are less affected by surface disturbances and can operate continuously for long periods, therefore providing a more accurate picture of the current structure.

4. How do ADCPs using the Doppler principle work?

Principles: The working of ADCPs is based on the Doppler principle. They send out high-frequency acoustic pulses into the water. If there are moving water particles interacting with these pulses, there will be a shift in frequency of the reflected pulses. If the movement is toward the ADCP profiler, then the reflected signal is at a higher frequency from what was emitted; in another way round, it's at a lower frequency.

The ADCP meter has several transducers, which send and receive the signal at different angles. This permits the device to analyze, through the Doppler shift from different directions and on different depths, the calculation of the three-dimensional water velocity. That means determination of the horizontal and vertical components of the velocity-the current structure and its inner behavior in detail.

5. What is necessary for good quality measurement of Akita coastal currents?

The equipment should be made of appropriate, reliable materials for high-quality measurement of the currents near Akita. Durable casing is very much required because of the salty water, possible storminess, and tides with ocean currents. The overall size of the equipment should be small to allow for efficient laying and retrieval, given the complexity of the coastal topography, bays and headlands.

It should be lightweight; this would make the equipment easier to handle during installation and maintenance. The sensor should feature low power consumption to enable its application for long-term autonomous operations. The cost of instruments should also be as low as possible to realize large-scale measurement.

The casing of ADCPs is preferably made of titanium alloy. Titanium alloy is very resistance to corrosion, which is important in seawater with its corrosive effects. It is strong and resilient enough to handle the different water pressures, and yet light enough for easy handling with various deployment methods.

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

First, the purpose of use should be considered when choosing equipment for current measurement near Akita. For a vessel's navigation or short-term research, a ship-mounted ADCP flow meter would be suitable. It can provide real-time current information during the voyage.

For measurements near the seabed, such as for studying sediment transport or benthic ecology, a bottom - mounted ADCP is preferable. It can capture the details of the near - bottom current. If long - term and wide - area monitoring of the coastal current is required, 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 Akita, 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.