Wednesday, 23 May 2012

Flights over the Netherlands

The last few days have been very busy for the scientists, with flight planning based on chemical forecasts, instrument calibrations, layout changes, quick look data preparation there was little time for anything else. As we can work on this blog only when time allows, we would like to apologize for the lack of updates and summarize the recent events.

Saturday, May 19
On Saturday, we had a flight with the photochemistry-centred cabin layout. The Zeppelin was accompanied by the small research aircraft Sky Arrow of the University Wageningen.

At 11 am local time, the airship lifted off, heading towards Cabauw, where KNMI meteorological tower is located.

There, the Zeppelin flew in circles on several altitudes to get height profiles of atmospheric composition as measured with every instrument.

Coordinated with our Zeppelin flights, a NO2 sonde was released, to extend these measurements to higher altitudes.
At approximately 4 pm, the Zeppelin had to return, because bad weather was forecasted to come in. Due to this forecast, the Zeppelin had to be made lighter to be able to lift off its rear section while connected to the mast truck. In essence this means we had to take out some of our instruments and store them in the hangar in the meantime. This is greatly improving the safety of the airship at the ground at higher windspeeds.

Sunday, May 20
On Sunday, an inbound weather system grounded the Zeppelin. The scientists made the best of the situation and worked on detailed planning for the flights to come, their instruments and their data.

Monday, May 21
The secondary organic aerosol cabin layout was installed early Monday morning.

At 10 am local time, the airship took off, flight direction towards Gelderland in the east of the Netherlands.

After arriving there, a few circles were flown in different heights over a forest. After that, the Zeppelin flew to a measurement station south of Wageningen, where another height profile was measured. As soon as that was done, the flight continued west towards Cabauw, where KNMI scientists awaited the Zeppelin to release another NO2 sonde.

After circling on three height levels, the Zeppelin returned to Rotterdam the Hague Airport, where it arrived shortly after 4 pm. The data from this flight are thus for the first time providing us with height dependent information on the aerosol composition in the boundary layer.

As the weather prediction promised rain for the night, we had to uninstall two instruments again to counter the water weighing heavily on the Zeppelin hull.

Tuesday, May 22
According to the forecast for the visibility, which is a limiting factor for Zeppelin flights, the flight for Tuesday was scheduled for noon. Some work was done to replace a broken converter in the power supply rack in the Zeppelin. The occasion was used to also install some ventilation in that rack. Unfortunately, some problems were discovered that forced some of us to climb up the Zeppelin out on the airfield.

Unexpectedly, there was an inspection of the airship and all racks by the Human Environment and Transport Inspectorate of the Dutch Ministry of Infrastructure and the Environment. The inspection revealed no major problems, so we were allowed to continue our missions over the Netherlands.

Happy that it was still possible to fly that day, we watched the Zeppelin taking off at around 5 pm.

As our forecast model predicted a set of emission plumes along the wind direction from northeast, we had decided to do as many cross-sections between Cabauw in the east and the North Sea in the west as the predicted incoming weather would allow. Quick-look data from the instruments verified the existence of strong gradients in the measurements.

After flying to Cabauw  and from there back to the coast and about 30 km out on the sea, the flight ended at around 7 pm. Two instruments had to be removed again for the night to ensure safety for the Zeppelin.

Wednesday, May 23
Unfortunately the weather has a too high risk for thunderstorms, so the Zeppelin is not flying today. Safety goes first! And we probably can use some of the time for producing quick look plots of our data and compare observations with forecasts.

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