Science Flight #7 - May 10

On Saturday after suffering from the continuously bad weather, we finally encountered our preferable measurement conditions, a wide field of persistent boundary layer clouds. Unfortunately, these clouds were also quite stable above the airport. With the aviation weather indicating icing conditions above YEV, we were not permitted to start until the cloud base stepped up and we could start and approach the measurement area flying below the clouds. The low clouds were investigated North East of the Mackenzie Delta. Two cloud legs in north-south direction, one at 133° W and one at 129° W were defined. In between Polar 6 was intended to measure aerosol and trace gases while Polar 5 continued with remote sensing of the clouds and the atmosphere.

The flight went pretty well. We found that the two cloud legs differ significantly. While on the western one the clouds were thin easily to be penetrated by Polar 6 and ended before the northernmost point, the clouds in the east were quite thick and caused a lot of icing on Polar 6 again, when flying in the cloud top layer. In this area also an enhanced aerosol concentration above the clouds was indicated by AMALi. Some thin haze layers at about 10,000 ft altitude were also observed from the remote sensing on Polar 5. In coordination Polar 6 tried to sample these clouds in situ as Polar 6 was just about to finish an extended profiling of the cloud free atmosphere. On the second cloud leg, the situation remained stable with no significant changes. Similar to the first cloud leg a drop sonde was released indicating cloud top temperature of about -10°C. Due to some instrument problems, Polar 5 had to repeat the sampling of this cloud leg and separated from Polar 6. On the direct way home to Inuvik another significant change of the aerosol concentration above the clouds was detected by the lidar. This change was visible throughout the column up to 11,000 ft.

For details read here: http://www.uni-leipzig.de/~racepac/flights/flight_07.html 

Almost History - II

It's only two weeks ago when we still could drive on the ice road. Now that seems to be miles away. The road was already close in begin of May. The melting is so fast that almost all snow is gone and even the lakes start to build a liquid surface. The same holds for the rivers. Close to the shore water is already flowing while in the center the ice still is solid. As from south more and more melt water flows north the days of the ice road are counted.

First the ice will not longer resist the pressure from below and break up. But as long as the way to the Beaufort Sea is not free the ice flows will not be able to drift away. This drift will start later and quickly. Usually then the ice is gone within a day. The negative consequence of the breaking ice are the mosquito. One of them was sighted already today. 

Almost History - I

The Sir Alexander MacKenzie school was! one of the most significant buildings in Inuvik and gave the center of Inuvik it's own view. Yes, it was!

When we arrived in Inuvik, we were surprised to find this impressive building in a bad shape. All walls have already be removed giving a strange view into the number of class rooms. Some of them looked as if still all inventory is present and classes may start at all time. However, the school was obviously closed and something should happen to the building either renovating or turning it down. A new school was already build some years ago not far away behind the North Market. 

Nothing happened during the first days, but then suddenly on one morning walking to the Aurora institute three big excavators stand in front of the school. Little later they started their work... Just tier it down. The workers must have had a lot of fun. The wooden walls were easy to break with the heavy machines. After an hour already big parts of the long stretched building were on ground level. Local citizens watched this spectacle, so did we. In the afternoon the show was over and a big heap of rubble remained on the site. 

For us it was a little sad to see the view of Inuvik change so dramatically. But later we learned that not all locals ware sad. This is due to the history of the MacKenzie school. Build in 1959 the school is a symbol for the compulsory integration of the first nations (the various aboriginal peoples in Canada) into the western society what meant also learning English, etc.

  

Science Flight #6 - May 8

After yesterday we had neither good chances to get airborne nor any area where we located good measuring conditions, for Thursday we planned an flight at 10 am. Unfortunately, the low level clouds of interest did not remain only above the sea but also in Inuvik, including some flurries in the morning. So the take-off had to be postponed to 12 local. Due to the later departure and an approaching midlevel cloud band moving eastwards into the measurement area, the planned rectangular flight pattern was skipped by only flying the easternmost leg.  

Polar 5 reported very good measuring conditions for remote sensing. A solid uninterrupted stratus cloud deck with 8/8 coverage at low levels was present all the time between roughly 1500 ft and 3000 ft. Different to the clouds the surface below the clouds was quite in-homogeneous with a mixture of open water, small and large ice flows. This looked very interesting for our investigations. Overall the wind in the area were very calm and conditions were stable. So the lidar profile showed an almost perfect symmetry for the flight in both directions.



Below Polar 5, Polar 6 sampled the cloud top entrainment zone in a long ''linear'' flight path for about 43 minutes. Sampling the cloud top was done at different altitudes, once inside the cloud, once closely above cloud top. Towards the end of leg significant icing on aircraft and wing probes occurred (as well as at the sampling inlets) such that the aircraft could not enter the clouds afterwards anymore. So Polar 6 returned directly to Inuvik performing a long staircase for aerosol and trace gas measurements in the cloud free, clear air for 100 minutes. 

For details read here: http://www.uni-leipzig.de/~racepac/flights/flight_06.html 

Campaign Photo

As it is tradition for a field campaign, we also took a campaign photo with "all" participants. This one was made during the first week of RACEPAC. Unfortunately by now more than half of the people which are on the photo traveled already back home. Therefore new crew members arrived as exchange. Today the last new participant was picked up at the airport. So we are more than at half time.

In total 38 scientists and engineers participated during RACEPAC. Additionally the crews of Polar 5 and 6 count 9 people including four pilots, three co-pilots and two engineers. All the exchange had not been on a specific day, so one picture with all people is unfortunately not possible. We may take a second one.

Science Flight #5 - May 6

Seemed for us to be like a Déjà Vu: Again a frontal system with light precipitation crossed Inuvik during the night and the early morning. Similar to the flight on April 30, we intended to follow the front after it had passed and sample low clouds in its back. The forecast predicted an increasing cloud top altitude towards East and closer to the front what we could confirm pretty well during the flight. Takeoff was scheduled for 11 am. Even the front passed a little earlier, we kept to this schedule. This flight Polar 5 was to start first. Unfortunately takeoff of Polar 6 was delayed due to another aircraft. The time difference could be minimized until the begin of the cloud leg with Polar 5 already slowing down to 120 kn observation speed during the ferry.

Forecast from ECMWF

Lidar signal indicating cloud top
for the grey shaded area in the forecast.

The cloud situation we found in the measurement area was surprisingly close to the forecast. At the start of the cloud leg only a low stratiform cloud layer remained. This cloud was also present later, when flying towards North East, but showed increasing cloud top altitudes. About 25 NM after starting the cloud leg a second cloud layer in higher altitudes about 2000 m was detected by AMAli. First this layer was thin enough to be pentrated by AMALi, later it almost vanished before about 30 MN to the return point the higher cloud layer thickened. The cloud top also increased so that we had to adjust the flight altitude to 11,000 ft. 

Polar 6 could sample these clouds at three levels during the flight: (1) the lowest fog layer, (2) thin layers/sheets of cloud sometimes only haze roughly between 3000 and 3500 ft, (3) layers of Stratus translucidus and sometimes Stratus translucidus undulatus above 7300 ft to 7600 ft. Straight legs and staircases were flown to sample droplets and ice crystals. Mostly liquid droplets were found to dominate the cloud. 

During all the time the horizon looked very hazy. Cirrus, although very homogeneous, was observed by the radiation measurements above Polar 5 almost all the flight. Polar 6 also tried to sample the hazy layer above the cloud for about 15 minutes before approaching Tuk for another overpass intended to inter compare the aerosol measurements at ground and in the air.  

For details read here: http://www.uni-leipzig.de/~racepac/flights/flight_05.html 

Science Flight #4 - May 3

In the night from Friday to Saturday, a frontal system passed Inuvik. After it went trough a wide field of low level clouds remained above the Beaufort Sea. The clouds were forecasted to become thinner and disappear during the course of the day. That's why the flight was scheduled early with take-off at 10 am local. The target area for the cloud sampling was chosen straight north of Inuvik up to 71° North.At the airport fog again delayed the departure about 15 minutes.

Soon north of Inuvik low level clouds showed up. A cloud top altitude of 900 m above ground was observed by AMALi, the backscatter lidar on Polar 5. Only a few miles later, a second cloud layer with tops of about 1200 m overlayed the lower clouds. These clouds remained with no visible variability until end of the leg. So we decided to release only one drop sonde which confirmed the two layer structure of the low clouds. Temperatures were quite warm with a cloud top temperature of about -3° C while in flight level -5° C were measured. During the entire leg high cirrus clouds were observed by eye and by the radiation sensors. For Polar 6 penetrating the cloud was easy, as only liquid droplets were found and no icing occurred. 

On the way back to the shore line the clouds did not change. Observations of glories indicate pure liquid water clouds. Sometimes large glories related to small particles and narrow size distributions were seen. The transition of the two layer cloud to a single layer cloud was again detected by the lidar. Surprisingly in the altitudes between both tops of the layers an aerosol signal was measured by AMALi. This single layer cloud remained during the overpass of Tuk. While Polar 5 did fly only once above Tuk, Polar 6 measured at different altitudes to connect the airborne aerosol measurements with the ground station in Tuk. On the lowest level, the people in the ground station could easily see Polar 6 what was a big success for this flight.

For details read here: http://www.uni-leipzig.de/~racepac/flights/flight_04.html