How can we measure the coastal currents of Trieste?

1. Where is Taormina?

Taormina is a jewel on the eastern coast of Sicily, Italy, a town that marries natural beauty with a rich historical tapestry. Nestled between the azure expanse of the Ionian Sea and the imposing presence of Mount Etna, Europe's most active volcano, it offers a breathtaking panorama that has enchanted travelers for centuries.

This is a city of ancient roots, with Greek colonists having established their colony here as far back as the 4th century BC. Evidence of that remains in the awesome Taormina Greek Theatre, an architectural marvel that has stood the test of time. It majestically sits on the cliff side, giving views of both the sea and landscape to boot; it is often used today as a place for cultural performances, ranging from classical plays to modern-day concerts.

Over the centuries, Taormina has been sculpted into shape by Roman, Arab, and Norman rule-all of whom stamped their indelible marks upon the architecture, culture, and food. Its narrow, hilly streets have lined elegant palazzos, charming churches, and lively piazzas, around which locals and visitors alike are entertained in Mediterranean-style. Before Taormina opens the Ionian Sea. The sea's waters are a real playground for colorful fish, continuing up to playful dolphins. Generally, the sea waters of this coast are clean and warm; for this reason, swimming and diving are also widely practiced in these waters. The bottom around Taormina is very diverse: with rock outcrops, sandy bottoms, and a number of undersea caves adding to the intricacy of the dynamics of the coastal currents.

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

The coastal currents near Taormina are influenced by the interaction of various factors in a very complicated way:

Tidal Influences

Tides, through the gravitational pull of the moon and the sun, are the most significant contributor to the behavior of the sea and its coastal currents. In the Ionian Sea, the tide is semi-diurnal; in other words, there are two high tides and two low tides per day. During the tidal variation, water comes in and goes out along a coast, therefore creating what are called tidal currents. Currents can vary by location, state of moon phases, and also by local topography.

Wind-Driven Currents

The local wind patterns have a deep influence on the coastal currents. It is subject to various winds, from the warm sirocco blowing from North Africa to the cooler tramontana from the north. The sirocco can push the surface waters along the coast with its hot and humid air, creating surface-level currents. On the contrary, the tramontana does the opposite and can change the direction of the water. Big winds are also able to produce waves that, interacting with currents, make flow conditions even more complicated.

Thermohaline Circulation

Temperature and salinity variations in the water are responsible for the thermohaline circulation, which influences the coastal currents along the coast of Taormina. In fact, the Mediterranean Sea, to which the Ionian Sea belongs, has relatively high salinity due to its poor connection with the Atlantic Ocean and high evaporation rates. In summer, the rise in water temperature can produce relevant density differences responsible for the movement of water masses and the creation of deep-water currents that may interact with coastal waters.

Topography-Induced Currents

The coastline and underwater topography around Taormina have a great influence on the currents. An irregular coastline, such as bays, headlands, and inlets, will make the currents converge, diverge, or change direction. The underwater features, such as reefs, submarine canyons, and sandbars, disturb the flow of water and may give rise to local eddies and turbulence.

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

Surface Drifting Buoy Method Surface drifting buoys are simple means for the observation of the surface -level coastal currents. They are provided with GPS (Global Positioning System) devices and other sensors. Deployed in the water, they move by the movement of the surface currents while their positions are traced with time. The researchers can therefore determine the direction and velocity of the surface currents based on the buoys' motion. Nevertheless, this is a surface-layer approach, which can be quite inaccurate because the buoys can be affected by winds and waves and may at times fail to follow the path of the current.

Anchored Ship Method

An anchored ship can also act as a platform in measuring the coastal currents. The current meters of the present day are deployed from the ship at different depths either with the help of a winch system or mooring line. The current meters record the speed and direction of water flow at different depths to give a vertical profile of currents. This method provides more detail than the surface drifting buoy method but is very time-consuming and confined to where the ship is anchored, in addition to much equipment and personnel.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP current meter is an advanced versatile tool in the measurement of coastal currents. ADCPs use reflected sound waves for measuring the water velocity at a variety of different depths. In general, these instruments are regarded as more efficient because they offer a continuous profile of the current velocity over a large column of water in relatively short time frames. The ADCPs can thus be deployed from ships, be moored on the seafloor, or attached to buoys; thus, this instrument can perform in quite varied applications. It has gained popularity over the years due to its accuracy and the real-time measurement of currents.

4. How do ADCPs using the Doppler principle work?

ADCPs apply the Doppler principle. In operation, when an ADCP current profiler sends an acoustic signal, which is a sound wave, into the water, it encounters very small particles suspended in the water, such as sediment, plankton, or even bubbles. These particles scatter the. In case the particles are moving with the water current, then this will cause a different frequency of the scattered acoustic signal back to the ADCP flow meter than that of the emitted one. This frequency difference, called the Doppler shift, is linearly proportional to the scatterer's velocity and hence to the velocity of the water current.

ADCPs usually have several transducer beams oriented at different angles. Measuring the Doppler shifts of the scattered signals from all these beams permits the ADCP to calculate three-dimensional components of the current velocity: east-west, north-south, and vertical components. This helps in understanding the complex flow patterns across the water column.

5. What is required to measure the coastal currents of Taormina?

Material Reliability

Reliable materials, especially the ADCP, should be used for high-quality measurements of Taormina's coastal currents. The casing of the ADCPs should highly be of a titanium alloy. A number of advantages result from the use of a titanium alloy. Firstly, it is very resistant to corrosion, which is an important aspect in the salty marine environment. This was important because the high strength-to-weight ratio of the titanium alloy means that the ADCP is strong enough to resist the hydrostatic pressure at depth without being too heavy to handle easily. This makes the equipment easier to deploy and maintain whether it is on a ship, moored to the seafloor, or attached to a buoy.

Small Size and Light Weight

The equipment should be small and light to enhance its portability and ease of deployment. In general, the smaller ADCP meter can easily be installed on small boats or buoys, which require less energy in operation. This becomes critical in applications that require long-term monitoring, when the equipment must be able to survive for periods of time by itself.

Low Power Consumption

Continually operating equipment means that low power consumption is highly critical. It may be considered limited in power sources, within the marine environment, particularly autonomous devices like a moored ADCP or even a buoy-mounted ADCP. Low power consuming equipment can go longer and keep running without experiencing any frequent replacement of batteries and recharging processes. This thereby minimizes overall costs and a reduction in many logistics challenges caused while collecting data.

Low Cost

To make large-scale measurements and an extensive monitoring of the coastal currents around Taormina, equipment needs to be economical. An ADCP with lower cost does provide a situation where more devices can be deployed so that, in essence, a more comprehensive coverage of the coastal area can be achieved. This again is helping much for understanding the spatial and temporal variability of the currents themselves and making predictions quite accurately.

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

Based on Usage Purpose

Shipborne ADCP: It is appropriate for large-scale surveying. It can be installed on research vessels and utilized in the measurement of the currents along the ship's track. Shipborne ADCPs are very often employed in mapping the general patterns of coastal currents over a wide area.

Bottom-mounted ADCP: ADCPs mounted at the bottom will work for very-long-term continuous current monitoring on the same ground, moored with the oceanic floor in which the present velocities and current directions are collected without interruption in one location; useful for further investigations of local conditions of time-dependent coastal circulation changes. These allow the capability for long-term, fixed-place studies of trend and variability for nearshore circulations, near, for instance, a port area or some areas of ecological special interest and care.

Buoyant ADCP: Buoyant ADCPs are attached to floating buoys. They can move with the water and provide data on the current conditions in different locations. This type of ADCP profiler is appropriate for monitoring the dynamic changes in the coastal currents, especially in areas where the currents are highly variable.

Based on Frequency

• 600kHz: ADCPs with a frequency of 600kHz will be able to operate effectively in water depths of less than 70m. They are generally used in shallow coastal waters such as bays, estuaries, and nearshore. This higher frequency enables detailed measurement in the shallow water column.
• 300kHz: 300kHz ADCPs are good for water depths of about 110m. Thus, they yield very good readings in moderately deep waters and find application in water bodies whose depth is not exactly shallow but also not too deep.
• 75kHz: ADCPs in this category run at 75kHz, so they work more for deepwater applications with their range extending as far as 1000 meters. Due to their range, they tend to penetrate further and are appropriate in measuring the open ocean current where the depth in the area concerned is more pronounced.

Several other brands well known in the markets include Teledyne RDI, Nortek, Sontek amongst others. However, China Sonar ​PandaADCP has been cost-effective while quality separation is not compromised. Constructed with all-titanium alloy material, it provides great endurance and performance at affordable prices. With a price that greatly agrees with the pocket, it is an economic-type ADCP, suited for quite a great deal of purposes that range from scientific research to coastal monitoring. For more information, you can visit their website at ​https://china-sonar.com/.

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