AWAC - Current Profiler, Wave Measurements, and Ice Profiler
With the Nortek AWAC, you get a current profiler, a wave directional system, and an ice profiler in one unit. You can measure the current speed and direction in 1-m thick layers from the bottom to the surface. Waves of all varieties are measureable, this includes long waves, storm waves, short wind waves, or transient waves generated by local ship traffic.
The AWAC is designed as a coastal monitoring system. It is small, rugged, and suitable for multi-year operation in tough environments. The mechanical design is all plastic and titanium to avoid corrosion. The AWAC is available in two transmit frequencies (1 MHz / 600 kHz) which allow of different deployment depths.
The sensor is usually mounted in a frame on the bottom, here it is protected from complications at the surface such as harsh weather, vandalism, and ship traffic. While safely located on the bottom It is operated in online or in stand-alone mode.
In stand-alone use, the raw data are stored to the internal data logger and power comes from an external battery packs. A variety of options are available with maximum deployment lengths of 4 months with hourly wave data or 8 months when using lithium batteries.
Online systems are a variety of possible communication configurations. The most common are long, offshore cables (max 5 km) or acoustic modems. Online systems can be delivered with backup batteries, protected cables, shore side interface units, and online software. Consult our [examples of online configurations].
The AWAC's extraordinary wave performance has largely to do with the optional Acoustic Surface Tracking (AST). The AST is basically echo-ranging to the surface with the vertically oriented transducer. The beauty of this method of measuring waves is that it circumvents the depth limits imposed by bottom mounted pressure and velocity measurements. Long waves (swell) and storm waves are rarely difficult to measure, however waves generated by local winds are challenging without AST. Moreover, the AST also gives you the ability to derive wave parameters based on times series analyses. This means that AWAC can directly measure wave parameters such as Hmax, H1/10, Tmean, etc. which other bottom mounted systems simply cannot.
A more detailed outline of the AST as well as the AWAC and online applications can be found in the AWAC brochure (PDF), found under related content.
Ice measurements with the AWAC Ice Profiler
The surface is a strong acoustic reflector and this is trus also when the water surface is covered with ice. As a result, the AWAC can be used to detect the interface between water and ice as an ice profiler. When compared with a reference measurements (either the pressure sensor or mean measurements during periods of open water), the AWAC can be used to estimate the surface ice thickness. This method was used already the winter 2008/2009 in the Arctic with very good results. Find out how we use the AWAC in this Ice Profiling Report.
Tidal elevation with improved pressure sensor
From the spring of 2011, an improved pressure sensor with an absolute accuracy of 0.1% of full scale is available for the AWAC. For a deployment depth of 20 m (and a 50m full scale sensor), this means the absolute accuracy of the sensor is 5 cm, which is within the requirements for many operational harbor systems
The AWAC software is used to configure the instrument for deployment, retrieve the data and convert all raw data files to ASCII. In order to calculate the wave parameters, you have the choice between the non-graphical QuickWave software and the graphical Storm software. For online systems which require data managements and generating content for internet use (e.g. processed results and graphical plots) , the SeaState software serves as the link for all your AWAC wave and current data. For a more detailed description please check out SeaState.