How can we measure the Parnamirim coastal currents?

1. Where is Parnamirim?

Parnamirim is a municipality found in the northeastern Brazilian state of Rio Grande do Norte. Parnamirim lies on the Atlantic Ocean and is bordered by the state capital, Natal. Being in this geographical location places Parnamirim at the center of an active coastal area.

Geologically, the area around Parnamirim is a combination of low coastal plains and sandy beaches. Offshore, the seafloor is dominated by a complex bathymetry with varying depths and underwater topographies such as sandbars, channels, and some small coral reef features. The underwater topographies play significant roles in controlling the local coastal currents. The city is influenced as well by the Potengi River, which runs close and discharges freshwater into the sea, consequently influencing the density and salinity of the shore's water.

Parnamirim is as old as it is broad. The indigenous people, including the Potiguar settlers, occupied the area. They continue to influence local heritage, folklore, traditions, art, and customs. Portuguese colonists began settling in the area during the 16th century and introduced new farming techniques and trade techniques. Parnamirim ultimately became a tiny but important seaside town, agriculture and fishing pillars of its original economy. The economy of the municipality today is diversified, industry, tourism, and services having equally significant functions.

2. How is the health of the coastal currents surrounding Parnamirim?

Parnamirim coastal currents are influenced by a complex interaction of several factors. One of the most important ocean currents in the Atlantic Ocean, the South Equatorial Current, plays an important role. As it's approaching the Brazilian coast, it's influenced by the topography and bathymetry of the region. The South Equatorial Current, approaching Parnamirim, is able to branch into secondary currents, creating an intricate pattern of coastal currents.

Large tides exist in the Atlantic Ocean. The semi-diurnal tidal regime creates typical changes in water level. Spring tides create higher tidal flow by the greater moon and solar gravity. Such tidal flow interacts with the South Equatorial Current and local coast geometry to compel the general direction of coastal waters. The tides also play a role in the creation of rip currents, which are narrow, fast currents offshore. Rip currents are dangerous to swimmers and are a major aspect of coastal safety.

Local prevailing winds, particularly the northeasterly trade winds, also affect the coastal currents. The winds can cause surface waters to move in a certain direction, leading to a wind-driven current. Wind-driven current is also connected with tidal current and with the South Equatorial Current, so that water flow pattern is a complex one. Bathymetry down the bottom off Parnamirim in the guise of coral reefs, channels, and sandbars either constitutes a jam or funneling effect on current flow. Channels, for instance, speed up the current, whereas coral reefs are like water barriers to be flowed past by the water.

3. How can one monitor the coastal water flow of Parnamirim?

Surface Drifting Buoy Method

Surface drifting buoy method is a traditional method of observing coastal water flow. Scientists place buoys equipped with tracking devices in the sea. By observing the drift of these buoys over time, they can determine the direction and speed of the surface currents. But this method has certain limitations. It only reports on the surface layer of the water column, and the buoys are highly susceptible to wind interference. Wind can cause the buoys to oscillate in a way that is not indicative of the true movement of the currents below.

Moored Ship Method

The moored ship method involves utilizing an anchored ship as a platform to measure the currents. The instruments are dropped from the vessel to measure the water flow at various depths. While the method provides precise vertical profiles of the currents, there are several disadvantages. The coverage in space is limited to the area around the moored vessel, and the ship is known to disrupt the natural flow of the water and therefore may taint the measurements. Additionally, having a ship moored for an extended duration may be logistically unfeasible and costly.

Acoustic Doppler Current Profiler (ADCP) Method

ADCP current meter is a newer and more efficient technology for the measurement of coastal currents. ADCPs can measure water current over a very extensive vertical range with accurate information regarding the velocity profile of the water column. ADCPs can be used from a very broad range of platforms including ships, buoys, and seafloor deployments. Ship - mounted ADCPs can take continuous data as they move, sounding a broad area in a relatively short period. Bottom - mounted ADCPs can make long - term, fixed measurements, and it is thereby possible for scientists to observe long - term trends in coastal currents.

4. What is the working principle of Doppler principle ADCPs?

ADCPs are based on the Doppler principle. They project acoustic pulses into the water. These pulses bounce off suspended particles such as sediment, plankton, or bubbles in the water. When moving water, the frequency of the backscattered waves is different. By measuring the difference in frequency, the ADCP current profiler is able to find the velocity of the water relative to the instrument.

Most ADCPs include a number of multiple transducer beams, typically four or more at an angle. This multi-beam set enables the calculation of water's three-dimensional velocity. The combination of these outputs, the ADCP is able to give an overall picture of the current velocity at differing depths in the water column. Data acquired by the ADCP can either be processed real-time or logged for later processing, providing significant data on the dynamics of coastal currents.

5. What's necessary for high - quality measurement of Parnamirim coastal currents?

In order to perform high-quality measurement of Parnamirim's coastal currents, the measuring equipment must possess certain significant characteristics. They should be constructed using reliable materials, possess minute sizes, be light in weight, utilize low power, and be of low cost. These specifications allow one to utilize a large number of instruments and possess complete spatial coverage.

Titanium-alloy-cased ADCPs are highly recommended. Titanium alloy offers excellent corrosion resistance, which is essential for long-term use in the hostile marine environment. It protects against the corrosive action of seawater, preventing damage to the internal structure of the ADCP. In addition, titanium alloy is hard but light, ensuring the durability and mobility of the instrument. Such a set of properties makes it possible to perform reliable and long-term measurements of the coastal currents in the Parnamirim area.

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

According to Application

Depending on its application, the kind of ADCP to be chosen will vary. Ship-mounted measurements are best carried out using ship-mounted ADCPs. They can provide current data in real time as the ship moves through the water, and the coverage area will be large in comparison to time taken. Bottom-mounted ADCPs are used for long-term, fixed-point monitoring. They are able to provide a continuous series of data over an extended time duration so that investigators can compare the long-term coastal current trends. Floating ADCPs are used in observing movement in large volumes of water mass, and they have the ability to provide valuable information on large - scale circulation regimes.

Depth-Based Selection

The frequency of ADCP should also be decided with reference to water depth. For water depths less than 70m, 600kHz ADCPs can be employed. They are able to deliver high-resolution measurement in shallow water. For depths up to 110m, 300kHz ADCPs are to be employed. For deeper water, i.e., up to 1000m, 75kHz ADCPs can be used.

There are a number of popular ADCP brands available in the market, including Teledyne RDI, Nortek, and Sontek. But for those looking for cost - saving alternatives, the ADCP manufacturer China Sonar's PandaADCP is highly suggested. Constructed from pure titanium alloy, it provides great performance at a very reasonable price. It is the perfect option for budget - sensitive users who still need to have good ADCPs for coastal current measurements. You can find out more about them on their official website: https://china-sonar.com/.

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