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| Titel |
Volcanic Ash Cloud Observations with the DLR-Falcon over Europe during Airspace Closure |
| VerfasserIn |
Ulrich Schumann, Bernadett Weinzierl, Oliver Reitebuch, Andreas Minikin, Hans Schlager, Stephan Rahm, Monika Scheibe, Michael Lichtenstern, Caroline Forster |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250045450
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| Zusammenfassung |
| At the time of the EGU conference, the volcano ash plume originating from the Eyjafjallajökull volcano eruption in Iceland was probed during 9 flights with the DLR Falcon research aircraft in the region between Germany and Iceland at 1-11 km altitudes between April 19 and May 3, 2010.
The Falcon was instrumented with a downward looking, scanning 2-µm-Wind-Lidar (aerosol backscattering and horizontal wind, 100 m vertical resolution), and several in-situ instruments. The particle instrumentation, including wing station probes (PCASP, FSSP-300) cover particle number and size from 5 nm to some tens of µm. Further in-situ instruments measured O3, CO, SO2, H2O, and standard meteorological parameters.
Flight planning was based on numerical weather forecasts, trajectory-based particle-dispersion models, satellite observations and ground based Lidar observations, from many sources.
During the flight on April 19, 2010, layers of volcanic ash were detected first by Lidar and then probed in-situ. The horizontal and vertical distribution of the volcanic ash layers over Eastern Germany was highly variable at that time. Calculations with the particle dispersion model FLEXPART indicate that the volcanic ash plumes measured by the Falcon had an age of 4-5 days. The concentrations of large particles measured in the volcanic aerosol layers are comparable to concentrations measured typically in fresh (age < 2 days) Saharan dust plumes. An estimation of the particle mass concentration in the elevated volcanic ash plume probed as part of a vertical profile over Leipzig at about 4 km altitude yields 60 µg/m3 (possibly 100 µg/m3), with an uncertainty of factor two. Of the total mass only less than 10 percent was residing in the particle size range below 2.5 µm. This emphasizes the need for adequate instrumentation to fully capture the size distribution of volcanic ash.
During April 29-May 3, a sequence of flights has been performed between Germany, Scotland, and Iceland. Lidar measurements have been performed in a distance between 0-200 km downstream the Eyjafjal Volcano in Iceland. On May 2, the Lidar and insitu measurements occurred above and within the upper part of the ash plume over the North Atlantic in a quasi-Lagrangian experiment 7 h later.. The data are now being used to determine the volumetric flow in the plume and the mass flux of particles in the size range of up to about 30 micrometers.
Major scientific and operational conclusions, include:
- Falcon measurements have been performed between April 19 and May 3, 2010: with 2- mm-Lidar, in-situ aerosols, CO, O3, SO2, H2O
- Particles sizes measured: 10 nm - 30 µm age dependent (mainly silicate, ammonia sulfate, more Na, K than in Saharan dust),
- Mass loading (about 60 µg/m3, Leipzig, 5 days) comparable to Saharan dust (< 0.2 mg/m3)
- 200 km distance, 3-4 h age: 40 km wide, 2 km thick, 15 m/s, sharply edged, strong wet convective turbulence, well mixed?
- 450 km distance (same plume), 7 h age: at upper plume edge: 400-3400 µg/m3, no 2-DC probe particles, mass flux > 3000 kg/s, strong chemistry
- Lidar signal and FSSP-300 signal strongly dependent on refractive index, ash density, particle size spectrum 1- 50 µm
- Mid-European airspace closure was justified until Sat. April 17; thereafter ageing ash clouds dominated.
- Keflavik/Iceland was found to be free of ash as predicted on April 29 - May 2
- The Quality of forecasts was found to be quite reliable for aviation planning
- For the future we recommend combinations of models + lidar + satellite + in-situ
- We suggest an improved linking between operations and academia
- The DLR Falcon will continue to operate as Emergency Aircraft for some time
Further scientific investigations (ash plume dispersion, aerosol ageing, mass concentration estimates, heterogeneous chemistry, comparison to other observations and models) have been initiated. The results had been provided to the German Weather Service (DWD) and others partly during the flights by satellite telephone and within 24 hours as quicklooks, and made available to the public by internet. The results had immediate impact on the decisions of the responsible agencies in Germany and the Volcanic Ash Advisory Centre (VAAC) in London. After the flights the Falcon inspections showed no obvious damage due to volcanic ash impact. |
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