INCA

funded by the European Community  through the Fifth Framework Programme

Interhemispheric differences in cirrus properties from anthropogenic emissions (INCA)

On this page reports for the individual flights are compiled, either from the scientists on board or from the pilots. Please click on the flight for the relevant report.
 

Test Flight:
 
 

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Ferry Flight:

Crew: Welser, Widmann (pilots), Hinz (flight engineer), Minikin, Baehr, Seifert (payload operators)
Take-off time: 08:13 UTC, Landing time: 10:24 UTC

The main purpose of this flight was the transfer of the Falcon from Oberpfaffenhofen to Glasgow Prestwick International Airport, the base of the INCA flight operations in the next three weeks. The Falcon already carried the full scientific instrumentation, however the polar nephelometer, the LMD hygrometer and the 2D-C probe were inoperative during this flight. All other instruments were working nicely, so the few problems found during the previous test flight were fixed successfully. The flight took us on a fairly direct route from Munich to Prestwick over the central Netherlands and the North Sea. At the cruising altitude of 35000 ft (10650 m) the Falcon was out of clouds for most of the time with the exception of a few thin cirrus clouds encountered for about 10 min during the first part of the flight. During descend water clouds extended from about 2400 m altitude down to about 200 m above ground. The Falcon landed in Prestwick in heavy Scottish autumn rain. (Andreas Minikin)

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Mission Flight 1:

Crew: Welser/Widmann (pilots) , Hinz (flight engineer), Petzold (mission scientist), Stock, Gayet, Seifert (payload operators)
Take-off 13:10 UTC
Landing 16:05 UTC

The first flight of the INCA Prestwick period was dedicated to probe a cirrus field approaching from SW. After take-off the Falcon was heading north to 59°N 5°W. From this turning point the cloud field was entered at flight levels 330, 310, and 290. Flight tracks were oriented SW - NE, being almost aligned with the wind. Each leg lasted about 25 min. The Falcon flew perpendicular to the westbound traffic from Europe to North America. The operation area was located NE from the flight corridor, so that polluted air masses were transported into the operation area. The cloud top was located at FL 330 with T = 222 K. Respective temperatures at lower flight levels were 228 K and 234 K, respectively. The tropopause was located at FL 340 (T = 219 K). The SW to NE oriented flight tracks partially covered cloud-free areas, which gives good sequences for in-cloud out-of-cloud comparison studies. At the end of the flight a climb into the lowermost stratosphere and a stacked descent towards Prestwick were performed. No cirrus clouds were observed above the thermal tropopause. All instruments were working well.

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Mission Flight 2:

Crew: Welser, Widmann (pilots), Hinz (flight engineer), Minikin (mission scientist), Auriol, Baehr, Krejci (payload operators)

Take-off time: 13:34 UTC
Landing time: 16:41 UTC

For today satellite images and model predictions indicated the presence of a pronounced moisture band east of the Scottish mainland with very strong winds blowing northward. Cirrus was expected to occur here, though latest satellite images shortly before take-off already indicated that probably due to subsidence in upper levels the cirrus was partly dissolving. After take-off  the Falcon flow east to a waypoint at 56°N and 2.5°E located above the North Sea. At flight level (FL) 330 maximal wind velocities of up to 58 m/s were found between 2°W and 0° longitude. Some thin cirrus was encountered here, however the cirrus field was indeed very scattered and appeared to be dissolving. Following the filed flight plan the Falcon turned north at the waypoint and flew in cloud-free air for about 10 min with the wind and then back to the west at a lower flight level (FL 300). During the northward flight leg fairly homogeneous cirrus was visually observed to the right of the aircraft, therefore we decided to return to the original waypoint but this time extend the flight to the east until reaching this cirrus, again at FL 330. Inside the cirrus we turned north and continued to stay in the cloud until about 58°N. Returning back south the same cloud field was penetrated again at lower level (FL 300) and then quickly left behind after turning west to the direction of Prestwick. We descended to FL 250 to enter a lower cloud field. This was found to already consist of mixed phase cloud particles. Heading home we climbed up to FL 370 to perform the routine stepwise descent profile. Temperature and ozone measurements showed that FL 370 was still below the tropopause. During the whole of the flight, when no cloud was present, condensation nuclei (CN) concentrations were rather high at the upper levels, reaching at times 4000 particles/cm³. In cloud concentrations were up to two orders of magnitude less. The presence of ultrafine particles, both in cloud and out of cloud, indicated that particle production occurred. Non-volatile particle fractions were significantly lower than observed during the previous mission flight of 27-Sep-2000.

In general we expect that this flight provided a very valuable data set for the case of dissolving cirrus. Total flight time was 3 hours 7 min. All instruments worked very well. (Andreas Minikin)

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Mission Flight 3:

Crew: Welser/Widmann (pilots) , Hinz (flight engineer), Petzold (mission scientist), Ziereis, Gayet, Seifert (payload operators)
Take-off 13:42 UTC
Landing 17:00 UTC

For this day strong southerly winds were expected throughout the whole troposphere. The Falcon was heading north of the Scottish coast at FL 330. During climb the cloud top was passed at 9800 m (T = 222 K). Like in the two flights before, a dissolving cirrus cloud field was probed. Clouds showed up to be very scattered at FL 330, with large cloud-free regions in between. However, few small haze particles seemed to be present in this cloud-free regions most of the time. The first part of the flight was spent probing a thin cirrus layer close to the cloud top (FL 330, T = 222 K) aligned with the wind, and at the very cloud base, flying against the wind (FL 310, T = 228 K). Within the cirrus cloud field, a very pronounced change of aerosol properties was observed. This change was observed on both flight altitudes. After finishing this pattern, the Falcon was heading back to the main island, looking for lee wave activities triggered by the hills of Northern Scotland. Lee wave clouds were observed only at lower levels, but not in the upper troposphere. The final climb to the lowermost stratosphere, followed by the stacked descent was performed along the lidar beam over Prestwick. Unfortunately, the lidar beam was blocked by thick low-level clouds. All instruments performed well.

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Mission Flights 4 / 5:

Morning flight

Crew: Welser/Widmann (pilots) , Hinz (flight engineer), Petzold (mission scientist), Stock, Auriol, Seifert (payload operators)
Take-off     08:02 UTC
Landing      11:07 UTC

Afternoon flight

Crew: Welser/Widmann (pilots) , Hinz (flight engineer), Minikin, Baehr, Gayet, Krejci (payload operators)
Take-off     12:57 UTC
Landing      16:15 UTC

For this day, a situation was expected, which permitted a quasi-lagrangian experiment. The morning flight was planned to head to SW towards the coast of Ireland to characterise an air mass with only few clouds in it. Forward trajectories indicated a slight lifting of this air mass during its transport to the NE of Scotland. This situation offered therefore the possibility to study the formation of young cirrus clouds in a beforehand characterised air mass.

During the morning flight, the air mass was probed at two levels, aligned to the wind and cross-wind.  The pattern was completed by a vertical profile from the uppermost free troposphere down to the flight altitude, which corresponded to –25 °C. At the upper level (FL 330, T = 228 K), only very few scattered cirrus clouds were found. On the other hand, several evaporating contrails and aged plumes were encountered. A very pronounced change in background aerosol size distribution and number concentration was observed at his level, as soon as the flight path was leading above a cirrus cloud field. This change in aerosol properties again appeared at the lower flight level (FL 280, T = 235 K). During the descent to FL 240, clouds were encountered at 8700 m (238 K), the cloud base was found at 7320 m (248 K). The lower flight level was partially in clouds partially out of clouds.

For the afternoon flight the flight pattern was chosen based on the results of forward trajectory analyses and latest satellite images to allow for probing the same air mass flown through during the morning flight. The first part of the flight was conducted in the area of NE Scotland and the Orkney Islands at an altitude of 8200 m (FL 270), where the temperature was -33 °C. Here, a very homogeneous, fairly dense cirrus field was entered twice. It consisted for most of the time of ice particles, but in-between, for short time periods, the presence of super-cooled water could be measured. For the second part of the flight the Falcon ascended to 10100 m (FL 330, temperature -44 °C). Since there was no higher level cloud visible in the target region, it was decided at this stage do deviate from the original flight plan and head towards the north east to probe the only higher level cirrus that could be visually observed from the aircraft. On the way back, a descend profile down to FL 240, corresponding to the one in the morning flight, was not allowed by the air traffic control due to military operations. The flight ended with the usual climb to FL 370 end the step descend. During the descend scattered cirrus clouds with the typical shape of wave clouds were observed and partly probed.
Unfortunately, during the second flight the 2D-C probe was not working due to a failure of the laser, but all other instruments worked fine. (Andreas Petzold, Andreas Minikin).

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Mission Flight 6:

Crew: Welser, Widmann (pilots), Hinz (flight engineer), Minikin (mission scientist), Auriol, Baehr, Seifert (payload operators)
Take-off time:     10:18 UTC
Landing time:      13:35 UTC

This flight was planned to coincide with ground based measurements by the AWI lidar and with a satellite overpass over Prestwick. The meteorological situation was such that at upper altitudes high latitude air carrying humidity was advected by the jetstream from the north. While cirrus clouds where expected to appear in upper layers there seemed to be a good chance of having no lower clouds. For the first part of the flight a pattern was chosen where several flight levels between FL 270 and 350 were flown roughly in southwest/northeast direction north of Glasgow including several overpasses of Prestwick. Cirrus clouds were rather scattered, but visible at different altitudes. Near Prestwick cirrus was encountered by the Falcon mainly at FL 310 (temperature 250 K) and FL 330 (240 K), however, it turned out that the lidar could not detect the same clouds concurrently because of a persistent cloud cover at lower altitude. Since the cirrus in the region seemed to be dissolving and actual satellite images indicated the advection of cirrus clouds from the north the second part of the flight was directed towards the north of Scotland’s coast. The air was cloud-free for almost 45 min of flight at FL 370. Then a thin cirrus band aligned with the wind was found and followed inside at FL 330 (240 K) until to 59.3°N. The aircraft returned in the same cloud at the same altitude, which may allow for some later analysis of short scale temporal development. Aitken mode condensation nuclei concentration were generally remarkably low during the flight (between 30 and 100 particles/cm³), however it seems likely that a number of aircraft plumes have been crossed due to rather heavy aircraft traffic in the area. Particle production was observed as well. During the step descent near Prestwick cirrus clouds were penetrated again at different altitudes. This time ice clouds were present down to FL 210. There were no problems with the instruments with the exception of one channel of the Noy instrument not working, so there are no particulate NOy data available this time. (Andreas Minikin)

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Mission Flight 7:

Crew: Widmann, Scherdel (pilots), Hinz (flight engineer), Minikin (mission scientist), Gayet, Seifert, Stock  (payload operators)
Take-off time:     15:14 UTC
Landing time:      18:25 UTC

Today’s satellite images showed that cloud fields at high altitudes were present over the North Sea area moving counter-clockwise around the Scottish mainland due to a rather stable low pressure system situated over Great Britain. The higher cirrus clouds in that area north of Scotland were expected to be relatively cold, which is one of the main reasons why today’s flight was directed there. After take-off at late afternoon the Falcon headed first north-west towards Stornoway on Lewis, one of the Outer Hebrides islands. The time of flight was chosen to coincide with an overpass of the NOAA-14 satellite over that area. At the time of the overpass the Falcon just entered a cloud-free area after having been in a cirrus cloud field close to the top of the clouds at flight level (FL) 280 for some minutes before, so that a comparison of in-situ data with satellite derived data is possible in this case. The Falcon continued to fly north up to 61°N and then turned east continuing to the region of the Shetland islands. This flight leg was situated all the way inside a large and fairly homogeneous cirrus field with the top of clouds gradually increasing from FL 280 to FL 300. Over the Shetland Islands we entered a triangular flight pattern with one leg flown against the wind and one perpendicular to the wind. This was done at two flight levels with the upper one at FL 330. Thin, somewhat patchy cirrus, visually hardly visible after sunset, was encountered here at a temperature of –55°C, where only very small ice crystals were detected. On the homeward flight we climbed to FL 380, which proved to be well inside the lower stratosphere, followed by the usual step descend. It was very interesting to see that the troposphere this time was rather polluted up to an altitude of 7000 m but very clean higher than that. There were no major instrument problems, so this flight produced again plenty of cirrus cloud data, fortunately this time also including cold cirrus. (Andreas Minikin)
 

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Mission Flight 8:

Crew: Widmann, Scherdel (pilots), Dreiling (flight engineer), Minikin (mission scientist), Auriol, Krejci, Ziereis  (payload operators)

Take-off time:     10:58 UTC
Landing time:      13:28 UTC

The first of today’s flights was planned to include several overpasses of the ground based AWI lidar at Prestwick to provide in-situ data for comparison with the lidar measurements. Furthermore, there was a Terra satellite overpass in this area at 11:54 UTC. During the first hour of the flight the Falcon flew over Prestwick at different altitudes from east to west and back. However, again due to the presence of  low level clouds, lidar measurements were not possible at the same time. Since there were only very few cirrus clouds present in the Prestwick area anyway and because we had information from the ground that according to satellite images cirrus wave clouds were developing over the central highlands we then headed north-east. Cirrus clouds were indeed found in the area. They proved to be vertically comparably thick and laterally very patchy. Wind speeds were low in the area. Measurements were made at two flight levels, at FL 270 at a temperature of 227 K and at FL 260 at 230 K. The tropospheric air even at high altitudes was found to be again quite polluted with condensation nuclei concentrations up to 5000 particles/cm³ (Aitken mode) and CO higher than 100 ppbv. Particle NOy was higher than ever observed before during both INCA campaigns. There were no instrument problems during this flight. (Andreas Minikin)

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Mission Flight 9:

Crew: Widmann, Scherdel (pilots), Hinz (flight engineer), Minikin (mission scientist), Baehr, Gayet, Seifert  (payload operators)

Take-off time:     14:30 UTC
Landing time:      17:54 UTC

The second of today’s flights was dedicated to the investigation of a major cirrus field at relatively cold temperatures between the Shetland Islands and the coast of Norway. Similarly to the flight made two days before, the meteorological situation was dominated by a low pressure system over the British isles and the general wind direction in the target area was north-west. The transfer to the Shetland Islands area was made at FL 330, which was well in the stratosphere this time. During the descend into the cirrus clouds close to the target area the tropopause was found to be located at around 9000 m altitude (FL 300, 222 K, -51°C). The cirrus field appeared to be very extended in all directions, though with some gaps in-between, and the top of clouds reached up to FL 290. L-shaped flight patterns was flown at three different altitudes (FL 290, 280 and 270) with one leg aligned with the wind and one perpendicular to the wind. Embedded in the cirrus were cloud turrets caused by rather intensive convection as also indicated by the occasional presence of turbulence. On the way home to Prestwick the flight level was chosen at FL 260 and below to enter the very many present convective and characteristically shaped wave clouds over the ocean and the Scottish mainland. Turbulence was encountered several times indicating strong updrafts extending into the upper troposphere. The last hour of the flight was already in twilight conditions (where the wave clouds  proved to be visually particularly attractive). Obviously at this time particle production was reduced in comparison to the first part of the flight. There were two relevant satellite overpasses during the flight, one of NOAA-14 at 15:21 UTC and one of NOAA-12 at 16:20 UTC.

This was the last mission flight with full scientific instrumentation during the second INCA campaign. There were fortunately no major problems with both, the aircraft and the complex instrumentation this time and during all of the campaign. For all scientists I would like to thank the excellent flight crew and everybody who contributed to the success of these measurements.

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Ferry Flight:
 
 

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