How can we measure the coastal currents of Genoa?

1. Where is Genoa?

Located in northwest Italy, Genoa is a city which contains both a lovely sea and an abundance of history and cultural traditions combined poetically together. Having the Ligurian Sea to its coastline, it forms one of the largest port cities in this part of the area and thus forms a fundamental element in the regional economic panorama.

Its topography curiously combines the general view of the Mediterranean coastline with the nearby Apennine Mountains. The coast includes charming beaches, rocky coves, and a thriving port-the heart of maritime trade for many centuries. The historic center of Genoa is a UNESCO World Heritage Site, with magnificent palaces, churches, and narrow, winding streets that whisper about its glorious past as a powerful medieval maritime republic.

The Ligurian Sea, stretching alongside the city of Genoa, is that part of the Mediterranean Sea famous for the clear and deep-blue waters which are substantially unchoppy. These waters have favored very much shipping, fishing, and different kinds of water recreation. All kinds of marine life, from brightly colored fish to dolphins, which can be seen often quite close to the shore, populate the sea.

2. What is the situation of the coastal currents close to Genoa?

The coastal currents close to Genoa are influenced by many factors: tidal forces are of great importance. Due to the inflow and outflow of tides in the Ligurian Sea, the water may be moved in and out of the coastal areas, creating a complex current pattern. These tidal currents are influenced by the gravitational pull of the moon and the sun, in turn. For this reason, spring tides, during which the gravitational pull of both the moon and the sun falls in the same direction, have stronger tidal currents than neap tides.

Wind is another critical factor: the prevailing winds of the area, such as the Mistral, a strong cold wind which blows from the northwest, push the surface waters of the Ligurian Sea and thus generate wind-driven currents. Where winds are reasonably steady over some time, there will be a piling up of water along the coast because of the wind, influencing the direction and speed of the coastal currents.

Thermohaline circulation also plays a role, although less prominently. The variation of temperature and salinity of the water in the Ligurian Sea could form deep-water currents that are slow moving. Warmer, less saline water may easily go over the top of colder, more saline water, creating a very complex three-dimensional current system.

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

Surface Drifting Buoy Method

In the method of surface drifting buoy, buoys are laid on the water surface. These buoys are prepared with some tracking devices like GPS receivers. Carried by the surface currents, the positions of the buoys are continuously monitored. By analyzing the movement of the buoys over time, scientists can estimate the direction and speed of the surface currents. However, it yields information about only the surface layer of water and may be influenced by wind-induced movements, which may not be representative of the current flow in reality.

Anchored Ship Method

In the anchored ship method, a stationary ship is used as a platform. Current meters are suspended from it at different depths. These meters record the speed and direction of the currents at the depths on which they are situated. In this manner, one may be able to obtain information on the vertical structure of the currents; however, the spatial coverage is very limited. The measurement that is obtained is representative of the area surrounding the anchored ship and generally, the repositioning of the ship is an extremely laborious and expensive process.

Acoustic Doppler Current Profiler Method

The ADCP flow meter is an advanced, more efficient technique for coastal current measurement. They are also able to measure the speed of the current at various levels within a site. They utilize sound waves for detecting particle movement in water, which helps in presenting a detailed current structure profile right from the surface to the bottom. This technique gives high-resolution data and covers a relatively wide area compared to the anchored ship method, so it is preferred in modern coastal current measurements.

4. Operating Principles of ADCPs Employing the Doppler Principle

ADCPs work by the Doppler principle. An ADCP sends a sequence of acoustic pulses out into the water. The sound waves reflect from small particles suspended in the water, which might be plankton, sediment, or even bubbles. If the particles are moving owing to the current, the frequency of the reflected sound waves shifts.

The frequency of the Doppler shift is proportional to the velocity of the particles and, thus, to the current velocity. By calculating the Doppler shift of the reflected sound waves in different layers of depth, the ADCP calculates the current velocity in those depths. The ADCPs generally have several (usually four or more) acoustic beams angled downward. The signals received from the several beams are combined to give the three - dimensional velocity of the current.

5. What's needed for high - quality measurement of Genoa coastal currents?

Equipment Requirements

For high - quality measurement of the coastal currents of Genoa, several characteristics are desirable in the measuring equipment. First, material reliability is paramount. The equipment must be able to resist the harsh marine environment: from saltwater to strong winds and variable temperatures.

The size of the equipment should be minimal. The smaller the size, the easier the deployment and less interference with natural current flow. It also needs to be designed light in weight to minimize handling labor, especially when deploying from ships or small boats.

It should consume low power, especially for long-term measurements. In this way, the equipment will be able to operate for long hours without changing batteries frequently or using a big power source. A low-cost design is also preferred so that a large number of units can be deployed for full coverage of the coastal area.

Titanium Alloy for ADCP Casing

The housing of the ADCP will be of a titanium alloy casing. Some advantages of titanium alloy include high resistance to corrosion. This is one major point in regard to its possible longtime usage in the saltwater, Ligurian Sea. The metal can bear the action of sea water, oxygen, and other reagents within this water environment without major degradation. The usage of the titanium alloy is also comparatively light with other high-strength materials such as steel. This helps in reducing the overall weight of the ADCP meter, making it easier to handle and deploy. Besides, it has high strength that guarantees the ADCP current meter will resist mechanical stresses associated with deployment and operation in the marine environment.

6. How to Choose the Right Equipment for Current Measurement?

Based on Usage

• Ship-borne ADCP: This is the ADCP installed on a moving ship. It is appropriate for large area current measurements during the transit of a ship. Ship-borne ADCPs can provide a continuous profile of the current along the track of the ship, and they are useful in large-scale oceanographic surveys.
• Bottom - mounted (Sit - on - the - bottom) ADCP: These are deployed on the seabed. They are ideal for long-term, fixed-point measurements of currents. Bottom-mounted ADCPs can record the current velocity and direction at a specific location over an extended period, thus giving very valuable data for the understanding of the local current patterns.
• Buoy - mounted ADCP: Buoy-mounted ADCPs are installed on floating buoys, and they can measure the currents in the upper water column while the buoy drifts with the surface currents. Such types are useful in studying surface-layer current dynamics and their interactions with the atmosphere.

Based on Frequency

The choice of the ADCP frequency is related to the depth of water. With a higher frequency, a 600kHz ADCP will be able to work in water with less than 70m depth. The higher the frequency, the more detailed the measurement it can obtain in shallower waters. A 300kHz ADCP is suitable for water depths up to approximately 110m. For deeper waters, about 1000m, a 75kHz ADCP is commonly used. Low frequencies can travel deeper in water but may give a lesser vertical resolution compared to higher-frequency ADCPs.

The popular brands under consideration are Teledyne RDI, Nortek, and Sontek. Herein, customers may find a rather fair deal in this low-cost but good-quality ADCP, called Sonar PandaADCP made in China. It comes fitted with a completely constructed titanium alloy body, thereby allowing it to be hugely corrosion-resistant. With an excellent cost-performance ratio, it is an economic ADCP providing reliable data for coastal current measurements. 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.