How do we quantify the coastal currents of Havana?

1. Where is Havana?

Havana, the capital city of Cuba, is located on the northwestern coast of the island nation. It is located on the Gulf of Mexico, i.e., on the Bay of Havana. The bay is a natural harbor, which has been crucial for Cuba's sea trade and past development. The city is encircled by a unique geographical landscape. To the north, the huge expanse of the Atlantic Ocean lies before it, and to the south, the land falls away into the green, tropical interior of Cuba.

In terms of population, Havana has over 2 million people, the most of any city in Cuba. The city itself is an active mosaic of Cuban culture, blending a vibrant diversity of Spanish colonial architecture, Afro - Cuban elements, and the intense national identity. Colorful, centuries - old buildings constitute the streets in Old Havana, a UNESCO World Heritage Site. The residents in the city are renowned for their hospitality, welcome, and deep passion for music, dance, and art. Festivals like Carnaval de La Habana are a glorious display of the city's cultural extravagance, with lavishly adorned parades, musical concerts, and traditional dress.

2. What is the condition of the coastal currents off Havana?

The coastal currents off Havana are influenced by a number of factors. Tidal forces play a dominant role. The usual ebb and flow of tides in the Gulf of Mexico cause water to enter and leave the Bay of Havana, creating a cyclical motion in the coastal currents. The tides are governed by the moon's gravitational force and the sun's, and their frequency and strength can vary throughout the month.

The wind regimes have a very important role. The northeast trade winds blowing in the Caribbean have the ability to force surface waters, generating coastal surface-level currents. The hurricane season tropical storm winds have the ability to generate extreme changes in the direction and speed of the currents. Also, the fact that the Gulf Stream, a strong ocean current in the Atlantic Ocean, indirectly influences the coastal waters of Havana. Although the Gulf Stream does not directly flow through the Bay of Havana, its influence on the overall oceanic flow in the region can influence the local coastal currents.

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

Surface Drift Buoy Method

One method to monitor the flow of coastal waters is by the use of surface drift buoys. They are buoyant instruments with built-in GPS monitoring systems. Released into the sea, they flow with the surface currents. Observing the time-dependent position of these buoys allows researchers to calculate the direction and rate of the surface - layer flow of water. But this method provides information only on the surface of the water column and is vulnerable to wind-generated waves.

Anchored Ship Method

Anchored ship technique is applied in which a vessel is anchored off the coast in a particular location. Current meters are then suspended from the ship at various levels. The speed and direction of the water currents at these levels are measured by the meters. Though the technique is capable of creating a vertical profile of currents, it can be limited to a single point and can also be affected by the presence of the ship itself, which disrupts the original flow of water.

Acoustic Doppler Current Profiler (ADCP) Technique

The Acoustic Doppler Current Profiler (ADCP) has become a better and simpler means of coastal current measurement. ADCPs are highly effective since they can provide real-time, high-resolution data along a large vertical profile in the water column.

4. How do ADCPs working on the Doppler principle work?

ADCPs operate on the Doppler principle. They send acoustic pulses into the water. When such signals hit particles in the water, say sediment or tiny marine animals, the signals are scattered towards the ADCP. Scattered signal frequency is different from the original emitted frequency. This difference, known as the Doppler shift, is proportional to particle velocity and thus water flow. Through such quantification of this Doppler shift at a range of different depths, the ADCP will be able to calculate the water flow speed and direction at more than one level in the water column and attain a full comprehension of the structure of the coastal current.

5. What are requirements for high-quality measurement of Havana coastal currents?

For good and high-quality measurement of Havana's coastal currents, the measurement apparatus needs to meet some requirements. Durability of material is of overriding importance. The instrument has to be built out of materials able to survive in the harsh sea environment, for instance, corrosion due to seawater and mechanical abrasion. The instrument must be compact to limit interference with normal water circulation. Lightweight design is also valuable for application on cases where transport is essential, i.e., when being employed aboard small ships of research or used to set several devices in different places. Low power dissipation ensures long - term operation, which is essential, especially in remote coastal areas where there is no availability of power supply. Cost - effectiveness is an essential consideration as well, as it allows mass - scale deployment of the measuring instruments.

In the case of ADCPs, the material used in the casing is especially important. Titanium alloy is a great option for the casings of ADCPs. Titanium alloy possesses excellent corrosion resistance, which is essential for prolonged application in the salty and corrosive marine environment. It is also highly strength - to - weight ratio, thus being light and strong and capable of tolerating the pressure and physical stresses encountered in oceanic conditions.

6. How to choose the right gear for current measurement?

According to Usage

• Ship - borne ADCP: Extremely appropriate for enormous - scale measurements of coastal currents. Mounted in research vessels, it has the capability to stretch in a large distance and measure precise data because the ship is capable of covering enormous lengths of sea water, displaying meaningful information with regard to the spatial distribution of coastal flows.
• Bottom-mounted ADCP: Located on the sea floor, this is well suited for long-term observation at a fixed location. It is able to deliver continuous current information over extended periods of time, and this is useful in exploring the long-term behavior and trends of coastal currents.
• Buoy-mounted ADCP: Installed on buoys, it is applied to measure near-surface and surface currents. This type is convenient to put in places not accessible by boat or where permanent, unmanned surveillance is needed.

Based on Frequency

Frequency of ADCPs is also to be chosen cautiously. A 600kHz ADCP is suitable for water up to about 70m depth. It provides high-resolution data, and hence it is best for shallow coastal waters where specific information about the currents is desired. A 300kHz ADCP can be used up to 110m depth, with a compromise of resolution and depth of penetration. For greater depth, up to 1000m, a 75kHz ADCP will be more suitable since it will penetrate to deeper depths but of lower resolution than the higher-frequency models.

A few established makers of ADCP are present in the market, e.g., Teledyne RDI, Nortek, and Sontek. But for economically mindful individuals who don't want to settle on quality, ADCP manufacturer China Sonar PandaADCP of China is a suitable choice. It is an economical ADCP made with all-titanium alloy materials which are of high corrosion resistance and long life. Due to its remarkable cost-performance ratio, it is a suitable option for researchers and institutions looking forward to undertaking extensive coastal current measurements. For further details, go to their website at https://china-sonar.com/.

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