How can we measure the coastal currents of Dubai?

1. Where is Dubai?

Dubai is a glittering city in the United Arab Emirates, on the coast of the Arabian Gulf. It is famous for its opulent architecture, lively nightlife, and busy trade and tourism industries.

The cityscape is a blend of ultra - modern skyscrapers like the Burj Khalifa and traditional Arabian architecture. The high point of the place is the Dubai coastline, consisting of long sandy beaches, artificial islands like the Palm Jumeirah, and a busy port area. The waters of the Arabian Gulf off Dubai are warm and relatively shallow in many places. These waters host an incredible array of marine life, from colorful fish to corals and different types of shellfish.

The strategic location of the city on the Arabian Gulf has made it a vital center for international trade and shipping. It is a gateway for goods that flow in and out of the Middle East and beyond. The gulf also serves as a playground for water sports enthusiasts and a source of livelihood for the local fishing community.

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

The coastal currents off Dubai are influenced by several factors. Tidal currents are one of the most important. Because of the gravitational pull of the moon and the sun, the tides in the Arabian Gulf have a regular cycle of ebb and flow. The tidal range and strength of tidal currents can vary depending on the lunar cycle and local bathymetry.

The wind-driven currents also contribute to the general current pattern. The prevailing winds-the Shamal winds from the northwest in the region-can push surface waters and generate surface currents that are seasonal in strength and direction, which again would change the coastal circulation patterns. It is the interaction between this wind-driven and tidal currents which provides a complex current regime.

The topography underwater around Dubai also affects currents. Man-made structures such as the Palm Jumeirah and further offshore developments, and underwater topographic features like ridges and channels, may be deflected and alter the water flow. Shallow places may decelerate the current, whereas deep channels speed up the currents.

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

Surface Drift Buoy Method: In this technique, buoys are laid on the water surface and left to drift according to the currents. These buoys usually contain GPS or any other locating device. By mapping the buoy's position with respect to time, it would determine the direction and speed of the current flow on the surface. This generally gives information about the surface layer, which might not yield the vertical structure of currents.

Anchor Ship Method: In this approach, a ship is anchored at a specific location near the coast of Dubai. Instruments such as current meters are installed on the ship to measure the water flow around it. While this method can provide accurate measurements in the immediate vicinity of the ship, it has limitations in covering a large area and different depths simultaneously.

ADCP method: This is quite a newer, more effective, and proficient means of measuring coastal currents. The Doppler effect is utilized by the ADCP current meter to measure the velocity of water at discrete intervals from the water column. ADCP current profiler sends acoustic pulses into the water and receives the frequency shift in the reflected signals from the moving water particles. This, in turn, provides a well-defined idea about the vertical profile of the currents right from the surface to the seabed.

4. How do ADCPs using the principle of Doppler work?

Basically, ADCPs operate based on the principle of Doppler. They have transducers that shoot acoustic pulses into the water. As these sound waves come across moving particles of water, the frequency of the reflected waves is changed by the Doppler effect. The frequency shift is proportional to the velocity of the water particles relative to the ADCP meter.

Commonly, ADCPs have more than one transducer, with each intended for measuring water velocity in different directions. It is capable of calculating the three-dimensional velocity of the water-that is, the east-west, the north-south, and the vertical directions-by emitting pulses in these various directions and analyzing frequency shifts of the reflected signals. It also measures the time taken by the sound waves to travel from the transducer to the water particles and back. The frequency shift, combined with this information, is used in calculating the speed and direction of the water flow at different depths.

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

The equipment used has to possess certain characteristics for high - quality measurement of coastal currents in Dubai. The material used should be reliable and able to resist the harsh marine environment. The device must have a small size and light weight for ease in deployment and handling. Low power consumptions are also quite necessary to operate consistently, especially for long-term monitoring.

The casing of the ADCP flow meter shall be made of titanium alloy. This material provides excellent corrosion-resistant properties, which is important in the saline environment of the Arabian Gulf. It also has a high strength-to-weight ratio, which means it will provide durability while keeping the equipment relatively light. This material can withstand the pressure changes associated with different water depths.

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

While selecting equipment for the measurement of currents in Dubai, following criteria must be considered.

According to the purpose of use, types can be chosen. Suppose a ship-borne ADCP is used for installation on a vessel. Then the same can measure currents when the ship is in motion also, this will be helpful for covering the wide area of the coastal waters. The ADCP profiler with a bottom-mounted base provides stability of the measurement for currents passing above it, being particularly adapted for long-term monitoring of a given location. In turn, the buoy-mounted ADCP provides mobility, comfort, and speed in deployment while enabling measurements in different areas.

The frequency of ADCP depends on water depth. For water depths up to 70m, a 600kHz ADCP is quite adequate because it gives high-resolution data in shallow waters. A 300kHz ADCP will be suitable for up to 110m depth. A 75kHz ADCP is recommended for deeper waters such as those near 1000m, in order to measure with accuracy over a large vertical range.

There are well-known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, for a cost-effective option with good quality, the China Sonar PandaADCP is worth considering. It is made of all-titanium alloy material and offers an excellent cost-performance ratio. You can find more information on its website: https://china-sonar.com/.

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