Monday, 28 May 2012

Science at Sunrise

Guest Writer: Glenn M. Wolfe, University of Wisconsin, Madison

Like a delicious cake, that atmosphere is comprised of many layers. The thickness of – and mixing between – layers is determined by a number of meteorological phenomena that vary across time and space. Most terrestrial life on the Earth dwells in the lowermost region, the planetary boundary layer (PBL). Because humans are creatures of the surface, the immediate impact of our emissions is strongly felt here. This brings to mind the intriguing question of how the atmosphere would respond to a future world with flying cars, but I diverge…
The height of the PBL is mainly controlled by the sun. Solar heating at the ground warms the air, which rises while mixing turbulently with surrounding air (for an example of turbulent mixing, watch the steam rise from your coffee). The vertical extent of this mixing can be as much as 1 or 2 km on a hot summer’s day. At night, the PBL collapses and the region of mixing at the surface is shallower (less than 100 m).
These boundary layer dynamics can impact air quality. For example, pretend that the PBL is a box. We emit gases into this box at a constant rate.  If the height of our PBL box decreases by a factor of 10, then the concentration of gases (the amount per unit volume) will increase by a similar factor. In other words, we’re putting the same amount of pollutants into a smaller box. On the other hand, many secondary pollutants – such as ozone and particulate matter, the key components of urban smog – are only produced through sunlight-driven processing of surface emissions.
As a scientific platform, the Zeppelin affords the unique opportunity to characterize the transition from nighttime to daytime boundary layers – to unravel the complex confluence of chemistry and meteorology at sunrise. That is, if you don’t mind working by moonlight.

At 2:15 AM, a dozen drowsy scientists rallied in the hangar to begin flight preparations. An early start was needed to build two instruments into the cabin for the gas-phase photochemistry package (strong winds precluded doing this on the previous day). In defiance of sleep deprivation, spirits were high and we were all excited for this ambitious flight plan. The Zeppelin ground crew and pilots also worked efficiently to ensure an on-time take-off, and at 4:30 AM the airship departed for the Cabauw tower.

After conducting several height profiles around sunrise (6:00 AM), the airship returned to Rotterdam to refuel and then sped back to Cabauw. Based on computer models and previous tower measurements, our Dutch collaborators predicted that the daytime boundary layer would begin to develop around 8:00 AM. To capture this growth and its influence on atmospheric composition, the Zeppelin flew continuous height profiles near the tower.

After five such profiles, the airship returned to Rotterdam and docked at 11:00 AM. The scientists followed their normal routine of post-flight calibrations and celebrated a successful conclusion to our journey in The Netherlands.
We slept well that night.
Preliminary data shows that the Zeppelin did indeed dip in and out of the nascent PBL. Equally remarkable is the fact that all instruments worked properly throughout the flight – a rare occurrence on any field campaign. This truly unique dataset will provide new insights on the coupling between human activities and natural processes.

Google Earth overlay of the Zeppelin flight path (in yellow). The inset shows the altitude in meters as a function of time in blue.

Saturday, 26 May 2012

Zeppelin tracker now live

For the last flights in the Netherlands we exchanged the cabin layout back to the photochemistry package. You can now locate the Zeppelin online at:

So have a fun weekend and let us know if you saw the Zeppelin fly by.

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.

Friday, 18 May 2012

Transfer flight, Mainz-Finthen to Rotterdam

In the morning the weather looked very overcast so that we were not sure if it would clear up for the flight to Rotterdam.

Suddenly the clouds vanished so the Zeppelin could start the second transfer flight at 10:36. As we had good weather conditions the pilots could fly an additional round over the airport so quality assurance measurements could be taken and journalists took nice shots of the Zeppelin. Then we left to heading to Bonn-Hangelar for the tankstop.

On the way from Bonn to Rotterdam we passed Cologne, lignite opencast mining areas and the Forschungszentrum Jülich. Crossing the Netherlands east to west, we passed over different source areas.

Meanwhile the scientists from Germany, Finland, Switzerland and the Netherlands held a first airport meeting to plan in more detail for the next flights and coordinate with our partners performing measurements at Cabauw tower and on board the Skyarrow, a small aircraft equipped to measure meteorological parameters and CO2 and water vapor concentrations and fluxes.
At 18:00 the Zeppelin landed at Rotterdam the Hague airport, where we eagerly awaited it. The operators of the individual instruments got ready to enter the Zeppelin for data downloads, instrument service and calibrations. For the few meters from the hangar to the Zeppelin we have to wear reflective vests to be clearly visible. At 21:30 finally all work was finished for the day and we are looking forward to our saturday flight, where we want to explore the vertical distribution of trace gases and pollutants close to the Cabauw tower.

Some coverage of the Zeppelin landing at Rotterdam and our project can be found at:

Thursday, 17 May 2012

First transfer flight, Friedrichshafen to Mainz Finthen

After a delay of 3 days due to rainy weather conditions the Zeppelin equipped with the photochemistry package (CL-8) left the Friedrichshafen airport at 9:30. We had beautiful flying conditions, all the instruments worked without any trouble so far.. The weather was very sunny and cloudless. The outside temperature was about 5 °C so that the Zeppelin could reach heights of about 1500 ft above ground. The cold temperatures led also to good conditions in the gondola so that the scientist and the crew did not sweat a drop. 

On the ground meanwhile the equipment was packed by  the Ground crew and they made their way to Malmsheim the airport for the tank stop and than further to Mainz-Finthen.

The Zeppelin travelled past the svabian alp passing smaller cities as Sigmaringen, Tübingen and the castle Hohenzollern… flying mostly over rural regions covered with forest and some smaller villages heading towards Stuttgart. The measured concentrations of  the Nitrogen oxide, a pollutand mainly from traffic , showed the expected variations and to our surprise even showed the plume from Stuttgart at the forecasted location  but a bit more extended.

 At 11:15 the Zeppelin reached Malmsheim, which is close to Stuttgart, to make a quick refueling stop. Having spent 30 min on the ground we continued our way to Mainz-Finthen, flying over the highway A8 towards Karlsruhe passing Pforzheim.

Karlsruhe was reached at 12:30. The Rhine harbor, a region with a lot of industries especially refineries, was an excellent opportunity to observe the effects of these emissions on air quality. The Zeppelin cycled therefore at two heights over this region. The model forecast predicted low ozone in this aerea, the observation based on the quick look data confirmed. To see this kind of agreement of forecast and reality in realtime is really great.

Having spent 20 min cycling over Karlsruhe the Zeppelin continued its way towards Mannheim passing an agricultural region and the Rhine valley, different chemical conditions to be analzed.

Due to perfect weather conditions the Zeppelin reached Mainz-Finthen at 14:00, way before schedule. So additional measurements were possible above Mainz and the downstream Rhine valley.
At 16:45 the ground crew had prepared the mast, though they had  some delay by traffic, so that the Zeppelin could land.  We were welcomed very warmly in Mainz Finthen by a lot of people waiting to see the Zeppelin NT and our experiments.

As we could see in our quick look data, all instruments had worked well. So we secured our data, performed calibrations in the field, which is very different to the Zeppelin hangar and switched off our instruments for the night.

Start of transfer flight - finally!

Unfortunately, the weather did not permit the start of the transfer flight on monday, as it was planned.
Today the Zeppelin left Friedrichshafen to fly via Mainz/Finthen (D) to Rotterdam (NL). Along the flight route one should be able to spot the Zeppelin while it measures with the photochemistry layout.

The Zeppelin is expected to arrive at Rotterdam airport friday afternoon.
The instruments not currently on board are awaiting the airship in a Hangar on the airport already.

Saturday, 12 May 2012

Successful test flights with all cabin layouts and Top Platform

The last few days have been very busy, but also very successful. On thursday, the SOA (secondary organic aerosol) package went out on a hot and sunny day.

After the airship had done circles in three different heights over a close by forest, it returned quickly into the hangar, where the Top Platform was mounted.

After the mounting, there was still enough time to do the first 2012 flight with Top Platform.


We were all happy to hear from the scientists operating the Top Platform, that the laser was stable over all achieved altitudes and meaningful OH, HO2 and OH lifetime data were recorded.

On friday, the cabin layout was changed to the photochemisty package, which is also going to be used for the upcoming transfer flights to the Netherlands. While in the process ofexchanging racks, the pilots informed us, that weather with high windspeeds was about to pass through the region. Within one and a half hour, we would have to move out of the hangar to at least get a one hour flight. This was of course increasing pressure on the mechanics from Zeppelin Luftschifftechnik and the scientists responsible for the to be exchanged racks. With a combined effort, setup processes on the moving airship and last-minute hotfixes, we were ready just in time to have the last cabin layout take off on this day.

The flight was only relatively short, but all instruments worked properly. Quick-look data of the flights was discussed later in a relaxed atmosphere.

As the weather does not permit flights today and tomorrow, we are looking forward to seeing the airship flying to Rotterdam on monday morning.

Thursday, 10 May 2012

First Zeppelin test flight – a scientist’s experience

I was super excited and honored to be able to be part of the first Zeppelin test flight 2012. There’s just something overwhelmingly thrilling to see your instrument flight for the first time. To be exact it was the second time for the instrument, NAIS, but first for me. The first test flight with NAIS was made in November. NAIS is part of the nucleation package and it measures the size distribution of the atmospheric ions and total particles. NAIS measures ions from 0.8 nm up to 47 nm and particles from 2 nm up to 47 nm. With NAIS we are hoping to see how the size distribution is changing during a nucleation event and have data to compare with other instruments, which measure different variables.
The scientists are waiting for takeoff.
Like in every proper test flight, the schedule didn’t hold as planned. It took few extra hours to get the Zeppelin ready, but when everything was finally ready, we had to move fast. We were three scientists who got onboard, and waited for the take off seated. I got to sit next to the pilot. I was a bit nervous, after all it was my first Zeppelin flight and I quite didn’t know what to expect – flight wise and instrument wise. The take off was short and smooth. We floated up in the air. 

The NAIS is sampling through the window.
After the take off we were allowed to unbuckle ourselves and go to the instruments. My task was to get the NAIS inlet out of the Zeppelin window, since most of the inlets were suppose to be inside the aircraft during takeoff and landing.  So inlet out and wait for the first data. What a positive surprise it was to see that the instrument worked even better than expected. With a working instrument, I got to enjoy the flight and the view of Bodensee, Alps and the forest under us. I’m certain that this will be a great campaign!  

View from high above.

Tuesday, 8 May 2012

First test flights in 2012

Today we had our first test flights for 2012!

PEGASOS-Zeppelin's first scientific flight for 2012
Cabin layout number nine, consisting of CPN-, API-, NAS- and NOX-Racks

The instruments for  cabin layout 9 (CL9, nucleation) were already installed (tooled, as the specialists say) on saturday. For sunday, we had a bad weather forecast, so we had the chance for some free time (which most experimentalists still used for working on the instruments)

Sitting on the airfield with perfect weather

For today, the weather forecast was looking good, so we moved the airship out of the hangar at 10:30 a.m. After the pre-flight checks were done by the pilot, it was realized that switching the electricity for the racks from generator ground power to airship power did not work as expected. The troubleshooting turned out to be complex. After a few hours of hard work, the engineers and technicians of Zeppelin Luftschifftechnik managed to find and fix the problem.

Second airship with touristic passengers passing the PEGASOS airship
Spectral radiometer and inlet lines for API-ToF and CPN-Rack

As a consequence of that, we were able to start the first test flight at 3:30 p.m. After 3/4 of an hour, the scientific staff on board was changed and another 15 min flight was performed. All instruments on board seemed to perform well and quick-look data from the flight was later on discussed.

Second airship landing close to the PEGASOS Zeppelin
 After landing for the second time, the airship had to be moved quickly into the hangar because of increasing wind speeds. Under these rushed conditions, the electricity for the racks had to be switched another two times to get to power socket supply. These switchings were giving us trouble in November, but this time every switch went smoothly and we are very happy that we can now expect seamless power supply for the instruments.
PEGASOS Zeppelin landing