APMOS: An autonomous profiling measurement system for the ocean surface boundary layer

The ocean surface is a boundary layer between atmosphere and ocean. It is highly relevant for the exchange of momentum, radiation, gas and water molecules. To get a better understanding of the exchange processes through the ocean surface APMOS, an autonomous profiling measurement system for the ocean surface boundary layer, was developed. APMOS profiles the undisturbed water column aside from a research vessel and consists of a floating body as well as a profiler. Both bodies are connected through a cable and drifting passively with the water current. System parameters of the profiler like depth, position and inclination can be recorded wirelessly and the user can configure the dive depth in real time. The profiler is equipped with a CTD (Conductivity, Temperature, and Depth) sensor and due to its modular design other sensors can also be mounted. To achieve positive or negative buoyancy the profiler is equipped with two piston tanks. The APMOS was successfully tested in the Jade Bay (southern North Sea). The profiler descends with 0,2 m/s and rises with 0,1 m/s in a relative stable position with a maximum tilt of 10 degrees. Compared with other common measurement systems these rates are slower thus preventing from mixing through platform movement. The CTD sensor is installed as upward looking and performs measurements even through the ocean surface. Overall the system is inexpensive, weighs 20 kg and can be easily handled by one person. Data shown represent novel results from the first testing phase.