Aeronautics | 29. May 2015

WindVal: Petta reddast

Betanken der Falcon vor dem Start
Credit: DLR (CC-BY 3.0)
Falcon ready for the jet stream flight, in the background is the NASA DC-8

In Iceland you hear one phrase very often: 'petta reddast', which can be translated as "it will all work out okay". With that in mind, we started planning the flight to have a closer look at strong changes in the horizontal and vertical gradients of the wind speeds in the atmosphere, which is one of the key objectives of the ADM-Aeolus WindVal campaign.

When operating from Iceland, the ideal target region for such an endeavour is in or near a jet stream (fast flowing current in the atmosphere with a meandering shape) over the North Atlantic that is within range of the aircraft. The situation on Friday 15 May 2015 offered a great opportunity to address this aim and coordinate with the NASA DC-8 to observe strong jet stream winds. We have total of four wind lidar systems on the two aircraft, the DC-8 and DLR’s Falcon.##markend##

The night before the flight, a strong cyclone brought rain and strong surface winds to Iceland. A band of thick clouds extended from Iceland to the UK.

The clouds were moving eastward throughout the day, and the region behind the cloud front was calmer – just scattered low and mid-level clouds in cold Arctic air masses. In the beginning, the window for operating under good conditions was small, but it turned out that the low cloud coverage was ideal to observe the predicted strong westerly winds.

Credit: ESA
Christian Lemmerz from DLR checking the instrument before take-off

After the surface front passed the airport in Keflavik, the sky cleared and both aircraft took off at 16:00 UTC and turned southeast towards Scotland. After two hours of flying into steadily increasing winds, the Falcon turned back over Glasgow, Scotland. The DC-8 headed westward and observed lower-level winds on the way home. Four hours later, the Falcon returned to Keflavik. The operators and the flight planning crew were very pleased about this mission flight 'petta reddast'.

Andreas Schäfler from the DLR Institute for Atmospheric Physics in Germany commented, "Planning a research flight is exciting every single time. You follow the development of the weather over several days. First, you hope that promising weather develops as predicted; then, you keep your fingers crossed that the instruments work properly."

Credit: ESA
NASA DC-8 following the DLR Falcon on the way to take off

"In this case, we were very happy that the timing of our flight plan turned out to be perfect with respect to clouds as well as the air traffic control agreed with our flight plans. The instruments collected promising wind data, which bodes well for the coming data analysis. In addition to the test and improvement of algorithms for deriving winds in situations of strong wind gradients, this case offers the possibility of verifying the representation of jet stream winds in weather prediction models."

For the upcoming flights, we all hope that we keep the spirit of 'petta reddast'. The next flight will take the crew to Greenland to conduct detailed measurements over the ice sheet.

The WindVal campaign is being carried out to support ESA's ADM-Aeolus wind mission.