A simple wind measurement control loop was written for the Bebop2 quadcopter. It tries to keep the roll angle at zero to align with the wind. It works well if there is a certain wind speed and clear, non-turbulenced wind. The wind speed is going to be determined later from the pitch angle.

The SODAR is set up. An array of loudspeakers pushes a very loud, audible series of pulses into the air and receives the response from the atmosphere with microphones.

The wind direction and wind speed can be determined based on the reflections at the air layers (having a different temperature).

At noon a cloud layer starts to cover the sky. It starts to snow in the afternoon. During supper we see that the weather should stay like that the rest of the week. There is some chance that a time window might open again during the night.

The measurements require a stable boundary layer. Clear skies without clouds and cold air would be ideal. We prepare for flights in the night, but in the end we don’t. In between we watch the rocket launch.

It is hazy all day. The lighthouse disappears in the fog and you can not see the horizon.

Everything is covered with fine grown ice crystals. There is a jingling noise when running in it.

The 10m mast is put up and the instruments are connected and tested. The anchoring is done by wooden sticks that quickly freeze in drilled holes.

We fly some low circles with the SUMOs in the late afternoon. The moisture immediately settles as ice on the propeller and the leading edge of the wing.

The performance of the aircraft decreases slightly with the changed surface of the wings and the propeller. We land before it is critical. How nice that there is de-icing for man-carrying planes.

The last storm piled up the sea ice on the beach in up to 4m high walls, unfortunately. This bothers when starting and landing the unmanned aircraft and changes the meteorological conditions.

The measurement equipment has to be installed way out on the ice.

The mast will be erected tomorrow morning.

We are back in northern Finland (a report from the first trip will follow below). This is part of a measurement campaign over the sea ice of the Gulf of Bothnia (the northern continuation of the Baltic Sea), next to the island of Hailuoto.

Last year we could drive over the ice with the car. This year it is too weak (25cm instead of the required 40cm). We take the free ferry. 3MW of diesel-electric power push it through the broken ice. Only 30cm of water are under the keel at some points. You can see the lights from an icebreaker on the horizon. It is waiting to help ships loaded with wood from Oulu.

The unfriendly weather in Germany called for a de-icing of the aircraft. Here in the north it is crisp cold at -12°C. Just as winter must be.