How to Measure the Coastal Currents of Morioka?

1. Where is Morioka?

Morioka is a city in Iwate Prefecture, located in the northern part of Honshu, Japan. It's not a coastal city in a direct sense but is relatively close to the Pacific Ocean. The city is known for its historical and cultural attractions, such as the Morioka Castle Ruins and traditional crafts.

The local economy is diverse, manufacturing, agriculture, and some services. Although it is not directly on the ocean, its proximity to the ocean means that the coastal currents can have an impact on the local climate and related economic activities like fishing and shipping in the broader region.

2. The Coastal Currents near Morioka

Many aspects create the variability in the coastal currents around Morioka. For instance, the Kuroshio Current is one great influence in the nearby Pacific Ocean. This warm ocean current flows northward and is rich in nutrients; as such, it brings along its warm and nutrient-rich waters. It affects both the temperature of the waters and distribution of marine life on those coasts.

In addition are the tidal currents. The area has a certain range of tides; the ebb and flow of the tides create the current pattern. The general shape of the coastline and the underwater topography in adjacent coastal areas are major factors. Bays, headlands, and underwater ridges may serve to alter current direction and speed. Besides, the wind pattern, particularly the seasonal wind like the trade wind, is able to drive the surface current and influence the mixing of different layers.

3. How to Observe the Coastal Water Flow near Morioka?

Surface Drifting Buoy Method

A surface drifting buoy can be thrown in the nearby ocean's water to observe the surface current. The movement of a buoy is followed over some time using GPS or any other tracking system. However, this technique suffers from certain drawbacks. It gives details about the surface current only, and wind and waves might affect it. For instance, if the buoy is moved by a strong wind in some other direction than where the current is actually moving, one gets incorrect measurements of direction and speed of the current.

Anchor - Boat Method

Current can also be measured by an anchored boat, where instruments are lowered down to the water from the anchored boat for measurements at selected depths. Although this could give more depth-wise records than other methods, this also is not without drawbacks. By placing the boat in a stationary position, there is certain limitation on the area measurement with which it is not going to detect the entire range of change within a large coastal area.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP current meter method is an advanced and more efficient way of 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 provides 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, giving a more accurate picture of the current structure.

4. How do ADCPs using the Doppler principle work?

The operation of ADCPs is based on the Doppler principle. They send high-frequency acoustic pulses into the water. Interaction of these pulses with moving water particles changes their frequency of reflection. The reflected signal frequency is higher compared to the emitted one in the case of movement toward an ADCP profiler and lower when moving away.

The ADCP meter possesses a set of multiple transducers, capable of both transmitting and receiving signals with a changeable angle of attack. Since the device records Doppler shifts from many directions and also at many depths, it is able to compute the three-dimensional water velocity. It can establish the horizontal and vertical components of the velocity, hence rendering detailed knowledge regarding the current's structure and behavior.

5. What is needed for high-quality measurement of Morioka coastal currents?

It should have reliable materials that ensure high-quality measurement of coastal currents near Morioka. With saltwater, and potential exposure to storms with the influence of tides and ocean currents, a casing must be made that is durable enough. The size of the equipment should be small in size for easy deployment and retrieval, especially in the complex landscape of coasts that consist of bays and beaches.

A lightweight design is preferable as it can make the equipment more manipulative at installation and during maintenance. Low power consumption is also essential for long-and autonomous operations. Cost-effectiveness also comes in handy to ensure large-scale measurements are possible.

The casing of the ADCPs is preferably of titanium alloy. The primary reason for this is that Titanium alloy has excellent corrosion resistance, which is vital for being in seawater. These are also strong and robust enough to bear the forces exerted by water and water pressure at different heights. Its lightweight nature hence makes it more convenient on various deployment methods.

6. How to Choose right equipment for current measurement?

When choosing equipment for current measurement near Morioka, consider the purpose of use first. If the measurement is for a vessel's navigation or short - term research, a ship - mounted ADCP flow meter is a suitable option. It provides real - time current information during the voyage.

For the measurement near the seabed, for example, 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.

In the frequency of ADCPs, up to 70m, one would have a 600kHz ADCP. At a depth up to 110m, an ADCP frequency of 300kHz will be proper. For the deep water that might fall in places near Morioka, at depths greater than 1000m, one has a frequency of 75kHz for the ADCPs.

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.