How to measure coastal currents of Luzon?

1. Where is Luzon?

Luzon, the largest and most important island in the Philippines, is located to the north of the country's other major islands. It belongs to the geographical region of Southeast Asia, surrounded by the Philippine Sea on the eastern side and by the South China Sea on its western side.   Geographically, Luzon is a diverse island with varied landscapes. It contains long mountain ranges, such as the Cordillera Central in the north, which is said to be the dwelling place of mountains like Mount Pulag. The island also consists of extensive plains and valleys that are said to be fertile enough and good for agriculture. There are many rivers traversing the island. One of the rivers and the longest in the country is the Cagayan River, which has an important role in the water circle and transportation on the island.

As for human activity, Luzon is a very populated island, being the center of economic and political activity in the Philippines. It houses the nation's capital, Manila, which is one busy metropolis full of history and colorful culture. In its coasts, there has been this old industry called fishing; fishermen from those areas depend on the rich marine life that thrives in the seas around them. Tourism also plays a very significant role, especially in coastal resorts and beaches, such as Pagudpud in the north to Batangas in the south.

The adjacent waters of both the Philippine Sea and the South China Sea play an essential part in the coastal life of Luzon. The seas surrounding Luzon form part of a complex, diverse marine ecosystem. In some places, there are coral reefs, which maintain a great variety of fish and other sea organisms. Coastlines range from sandy beaches through rocky coasts to mangrove forests, which are an important habitat for many species and also a natural defense against erosion.

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

In the coastal currents around Luzon, several elements are in effect. The most widespread effective force is that of tidal currents. Due to gravitational pull from the moon and the sun, tides move in and out, therefore producing tidal currents which, regarding strength and direction, differ at different times in the lunar cycle and with varied topography of coastline and seabed.

But the winds of the monsoon affect them considerably. There are two monsoon seasons in the Philippines. During the southwest monsoon, or Habagat, winds blow from the southwest and push the surface waters along, creating generally one-way currents. In contrast, during the northeast monsoon, or Amihan, winds from the northeast produce different current patterns.

The topography or relief of the bottom shelf around Luzon also contributes to the modification of coastal currents. Depending on the form and depth of the submarine floor, there may be accelerations or decelerations. In the presence of submarine ridges or canyons, for example, currents will flow at right angles to them. In cases where islands or islets are off the coast, the continuity of the current is broken, so that splitting or eddying takes place accordingly.

Temperature differences in the water can also create currents. Warmer water at the surface tends to rise and be replaced by cooler water from deeper levels, creating a vertical circulation that can be important for the net flow in the coastal currents. Besides, the input of fresh water from the rivers on Luzon can change the density of the coastal waters and, in turn, affect the patterns of currents.

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

Further, the coastal currents of Luzon have peculiarities in both their velocity and flow rate. The velocity may be relatively slow in well-protected bays and lagoons to quite fast in regions where the currents arestricted or are influenced by strong winds or tides. The flow rate, on the other hand, is determined by the amount of water that passes through an area per unit time.

To measure these coastal currents correctly, advanced easy methods are indeed required. Amongst one such advantageous method, Acoustic Doppler Current Profilers can effectively work out for the same. ADCP current meter can provide detailed and continuous data about the water flow, flow's depth therein.

3.1 How do ADCPs using the doppler principle work?

Acoustic Doppler Current Profiler (ADCP) also work on the principle of the Doppler effect. They emit acoustic signals into the water. When these acoustic waves encounter moving particles in the water-such as sediment grains or small organisms-the frequency of the reflected waves changes. This shift in frequency is proportional to the velocity of the moving particles and, in turn, the velocity of the water.

The ADCP current profiler measure three-dimensional water velocity by broadcasting a multiple number of acoustic beams out at various angles. They are able to calculate the horizontal velocity and the vertical velocity components, hence giving a full explanation of the structure in the flow of water. The data collected is then processed and analyzed to provide correct information on currents on the coast.

3.2 What's needed for high - quality measurement of Luzon coastal currents?

Mechanisms needed for high-quality measurement of the coastal currents near Luzon take into consideration several factors; reliability of material equipment, for one-the device must be capable of bearing the severe conditions in the marine environment: the exposure to salt water, high humidity, and fluctuating pressures.

Other important factors can be the size, weight, and power consumption of the equipment. Smaller size and weight make deployment and handling much easier in situations where the measurement has to be done from a small boat or floating platform. Similarly, low power consumption ensures that the equipment can work for extensive periods without frequent battery replacements or any other source of external power.

Another very important factor is cost: the equipment should not be too expensive to make large-scale measurements possible. One of the most suitable materials for ADCP doppler in terms of casing is the titanium alloy. There are several advantages to this alloy. This is an extremely strong and resilient material; it resists the corroding effects of saltwater. At the same time, its density is comparatively low, which helps in keeping the weight of the entire device down. Besides, it has excellent thermal properties, which may be useful in the sometimes extreme temperature conditions of the marine environment.

3.3 How to choose the right equipment for current measurement?

In choosing the proper equipment for the measurement of Luzon's coastal currents, some factors shall be considered. First is the deployment mode required. There are several types of ADCP flow meter, depending on the mode of deployment.

An in-water ADCP installation would be appropriate for measurements that must be made from within a ship. Thus, it can be installed on the hull of any vessel to provide continuous measurements while the ship is under way through the water.

If the measurement is to be done from the seabed, a bottom-mounted ADCP can be used. The latter type of ADCP meter rests on the seabed and measures currents above itself.

For the floating platform application, one would rather go for a buoy-mounted ADCP. It is usually attached to a buoy and measures currents in the surrounding water.

Besides the mode of deployment, an ADCP frequency is usually chosen based on the depth of the water. A 600 kHz ADCP would be ideal for water as deep as 70 meters, providing high-resolution measurements. In general, a 300 kHz ADCP is best for depths within the range of 70 to 110 meters. For deeper waters, say up to 1000 meters, the 75 kHz ADCP is recommended since it allows deeper water to penetrate the measurement of currents with precision.

There are several popular ADCP profiler brands on the market, including Teledyne RDI, Nortek, and Sontek. Those seeking cost-effectiveness with high quality should look into the China Sonar PandaADCP. It consists of all-titanium alloy material, which is sufficient for it to stand in harsh marine conditions and be reliable. Besides, it has an incredible price-performance ratio. You can check it at its official website, or you can look it up using this URL: https://china-sonar.com/.

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