How to Measure Coastal Currents of Hamamatsu?

1. Location of Hamamatsu

Hamamatsu is a city in Shizuoka Prefecture, Honshu Island, Japan on the east coast facing the Pacific Ocean. It is quite well-renowned for its production in musical instruments, such as pianos and wind instruments, and also boasts good coasts and beaches.

It is an industrial cum manufacturing city, yet fisheries and tourism hold crucial places in the economy as well. Marine resources in the Pacific Ocean around Hamamatsu are affluent. The waters contain various types of fish such as tuna, bonito, mackerel, along with all kinds of seaweed and shellfish. This region falls under the area of influence of Kuroshio Current that pushes across warm water rich in nutrition for increased productivity in marine ecology.

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

The coastal currents near Hamamatsu are affected by multiple factors. The Kuroshio Current is a major influence. This warm, north - flowing ocean current 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 a significant role. Hamamatsu presents some tidal range, and in turn, the ebb and flow produce complicated current patterns. The shape of a coastline and underwater topography are thus very important. Bays, headlands, or submarine ridges may further alter the direction and speeds of currents. For example, water flows faster around a headland and is deflected into bays. Wind patterns, especially the seasonal winds like the trade winds, may provide the force for surface currents and mix different layers of water.

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

Surface Drifting Buoy Method: A surface-drifting buoy can be released into the water to observe the surface current. The movement of the buoy 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: An anchored boat can be employed for measuring current. The instruments used to measure the current are lowered from the anchored boat into the water at depth. This can provide more detail with respect to depth; however, it also introduces a host of other disadvantages. Because the boat is stationed in a fixed position, this limits the measurement area and perhaps does not totally capture the variability of the currents within a large coastal area.

ADCP Method: This is a far more advanced and efficient means of measurement of 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, thus providing full profile from surface to seabed. With less influence by surface disturbances, ADCPs have the capability to function continuously over long periods for a much accurate picture of the current structure.

4. How do ADCPs using the Doppler principle work?

ADCPs are based on the principle of the Doppler effect. They send high-frequency acoustic pulses into the water. The interaction with moving water particles alters the frequency of the reflected pulses. Particles moving towards the instrument have a reflected signal at a higher frequency than what was emitted, and particles moving away have a reflected signal at a lower frequency.

The ADCP current meter has multiple transducers that send and receive signals at various angles. By analyzing the Doppler shifts from different directions and at different depths, the device is able to 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 high-quality measurement of the Hamamatsu coastal currents?

The equipment should be made of reliable materials for high-quality measurement of the coastal currents around Hamamatsu. Since it is in a marine environment, with saltwater, possible exposure to storms, and the influence of tides and ocean currents, it should have a durable casing. The size of the equipment should be small for easy deployment and retrieval, especially considering the complex coastal landscape with its bays and beaches.

A lightweight design is preferred because it makes the equipment more manageable during installation and maintenance. Low power consumption is necessary for long-term and autonomous operation. Cost-effectiveness is also important to realize large-scale measurements.

The casing of ADCPs is best made of titanium alloy. Titanium alloys have great resistance to corrosion, which is very fundamental for resisting the corrosive action of sea water. It is also strong and capable of withstanding the pressure of water at different depths. Also, its lightweight nature makes it more convenient for various deployment methods.

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

Equipment selection for current measurement near Hamamatsu depends first on the purpose of use. If it is to be used for a vessel's navigation or short-term research, a ship-mounted ADCP will suffice. It provides 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 captures the details of the near-bottom current. If one needs to monitor the coastal current over a long period in a wide area, the buoy-type ADCP would be ideal.

For the frequency of ADCPs, in water with depths up to 70m, a 600kHz ADCP is good. For water with depths up to 110m, it is better to use a 300kHz ADCP. For deeper waters, which may be found near Hamamatsu, with a depth over 1000m, a 75kHz ADCP is recommended.

There are well-known ADCP 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.