Sensitivity estimations for cloud droplet formation in the vicinity of the high-alpine research station Jungfraujoch (3580 m a.s.l.)
Aerosol radiative forcing estimates suffer from large uncertainties as a result of insufficient understanding of aerosol–cloud interactions. The main source of these uncertainties is dynamical processes such as turbulence and entrainment but also key aerosol parameters such as aerosol number c...
| Main Authors: | , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-09-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/15/10309/2015/acp-15-10309-2015.pdf |
| _version_ | 1819225595204075520 |
|---|---|
| author | E. Hammer N. Bukowiecki B. P. Luo U. Lohmann C. Marcolli E. Weingartner U. Baltensperger C. R. Hoyle |
| author_facet | E. Hammer N. Bukowiecki B. P. Luo U. Lohmann C. Marcolli E. Weingartner U. Baltensperger C. R. Hoyle |
| author_sort | E. Hammer |
| collection | DOAJ |
| description | Aerosol radiative forcing estimates suffer from large uncertainties as a result of insufficient
understanding of aerosol–cloud interactions. The main source of these uncertainties is dynamical
processes such as turbulence and entrainment but also key aerosol parameters such as aerosol
number concentration and size distribution, and to a much lesser extent, the composition. From
June to August 2011 a Cloud and Aerosol Characterization Experiment (CLACE2011) was performed at the
high-alpine research station Jungfraujoch (Switzerland, 3580 m a.s.l.) focusing on the
activation of aerosol to form liquid-phase clouds (in the cloud base temperature range of −8 to
5 °C). With a box model the sensitivity of the effective peak supersaturation
(SS<sub>peak</sub>), an important parameter for cloud activation, to key aerosol and
dynamical parameters was investigated. The updraft velocity, which defines the cooling rate of an
air parcel, was found to have the greatest influence on SS<sub>peak</sub>. Small-scale
variations in the cooling rate with large amplitudes can
significantly alter CCN activation. Thus, an accurate knowledge of the air parcel history is
required to estimate SS<sub>peak</sub>. The results show that the cloud base updraft
velocities estimated from the horizontal wind measurements made at the Jungfraujoch can be divided
by a factor of approximately 4 to get the updraft velocity required for the model to reproduce the
observed SS<sub>peak</sub>. The aerosol number concentration and hygroscopic properties were
found to be less important than the aerosol size in determining SS<sub>peak</sub>. Furthermore
turbulence is found to have a maximum influence when SS<sub>peak</sub> is between approximately
0.2 and 0.4 %. Simulating the small-scale fluctuations with several amplitudes,
frequencies and phases, revealed that independently of the amplitude, the effect of the frequency on
SS<sub>peak</sub> shows a maximum at 0.46 Hz (median over all phases) and at higher frequencies, the
maximum SS<sub>peak</sub> decreases again. |
| first_indexed | 2024-12-23T10:12:05Z |
| format | Article |
| id | doaj.art-9f0e74f94cd548d1b959dd78faf33da4 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-23T10:12:05Z |
| publishDate | 2015-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-9f0e74f94cd548d1b959dd78faf33da42022-12-21T17:50:55ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242015-09-011518103091032310.5194/acp-15-10309-2015Sensitivity estimations for cloud droplet formation in the vicinity of the high-alpine research station Jungfraujoch (3580 m a.s.l.)E. Hammer0N. Bukowiecki1B. P. Luo2U. Lohmann3C. Marcolli4E. Weingartner5U. Baltensperger6C. R. Hoyle7Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, SwitzerlandLaboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, SwitzerlandInstitute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, SwitzerlandInstitute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, SwitzerlandInstitute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, SwitzerlandLaboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, SwitzerlandLaboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, SwitzerlandLaboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, SwitzerlandAerosol radiative forcing estimates suffer from large uncertainties as a result of insufficient understanding of aerosol–cloud interactions. The main source of these uncertainties is dynamical processes such as turbulence and entrainment but also key aerosol parameters such as aerosol number concentration and size distribution, and to a much lesser extent, the composition. From June to August 2011 a Cloud and Aerosol Characterization Experiment (CLACE2011) was performed at the high-alpine research station Jungfraujoch (Switzerland, 3580 m a.s.l.) focusing on the activation of aerosol to form liquid-phase clouds (in the cloud base temperature range of −8 to 5 °C). With a box model the sensitivity of the effective peak supersaturation (SS<sub>peak</sub>), an important parameter for cloud activation, to key aerosol and dynamical parameters was investigated. The updraft velocity, which defines the cooling rate of an air parcel, was found to have the greatest influence on SS<sub>peak</sub>. Small-scale variations in the cooling rate with large amplitudes can significantly alter CCN activation. Thus, an accurate knowledge of the air parcel history is required to estimate SS<sub>peak</sub>. The results show that the cloud base updraft velocities estimated from the horizontal wind measurements made at the Jungfraujoch can be divided by a factor of approximately 4 to get the updraft velocity required for the model to reproduce the observed SS<sub>peak</sub>. The aerosol number concentration and hygroscopic properties were found to be less important than the aerosol size in determining SS<sub>peak</sub>. Furthermore turbulence is found to have a maximum influence when SS<sub>peak</sub> is between approximately 0.2 and 0.4 %. Simulating the small-scale fluctuations with several amplitudes, frequencies and phases, revealed that independently of the amplitude, the effect of the frequency on SS<sub>peak</sub> shows a maximum at 0.46 Hz (median over all phases) and at higher frequencies, the maximum SS<sub>peak</sub> decreases again.http://www.atmos-chem-phys.net/15/10309/2015/acp-15-10309-2015.pdf |
| spellingShingle | E. Hammer N. Bukowiecki B. P. Luo U. Lohmann C. Marcolli E. Weingartner U. Baltensperger C. R. Hoyle Sensitivity estimations for cloud droplet formation in the vicinity of the high-alpine research station Jungfraujoch (3580 m a.s.l.) Atmospheric Chemistry and Physics |
| title | Sensitivity estimations for cloud droplet formation in the vicinity of the high-alpine research station Jungfraujoch (3580 m a.s.l.) |
| title_full | Sensitivity estimations for cloud droplet formation in the vicinity of the high-alpine research station Jungfraujoch (3580 m a.s.l.) |
| title_fullStr | Sensitivity estimations for cloud droplet formation in the vicinity of the high-alpine research station Jungfraujoch (3580 m a.s.l.) |
| title_full_unstemmed | Sensitivity estimations for cloud droplet formation in the vicinity of the high-alpine research station Jungfraujoch (3580 m a.s.l.) |
| title_short | Sensitivity estimations for cloud droplet formation in the vicinity of the high-alpine research station Jungfraujoch (3580 m a.s.l.) |
| title_sort | sensitivity estimations for cloud droplet formation in the vicinity of the high alpine research station jungfraujoch 3580 m a s l |
| url | http://www.atmos-chem-phys.net/15/10309/2015/acp-15-10309-2015.pdf |
| work_keys_str_mv | AT ehammer sensitivityestimationsforclouddropletformationinthevicinityofthehighalpineresearchstationjungfraujoch3580masl AT nbukowiecki sensitivityestimationsforclouddropletformationinthevicinityofthehighalpineresearchstationjungfraujoch3580masl AT bpluo sensitivityestimationsforclouddropletformationinthevicinityofthehighalpineresearchstationjungfraujoch3580masl AT ulohmann sensitivityestimationsforclouddropletformationinthevicinityofthehighalpineresearchstationjungfraujoch3580masl AT cmarcolli sensitivityestimationsforclouddropletformationinthevicinityofthehighalpineresearchstationjungfraujoch3580masl AT eweingartner sensitivityestimationsforclouddropletformationinthevicinityofthehighalpineresearchstationjungfraujoch3580masl AT ubaltensperger sensitivityestimationsforclouddropletformationinthevicinityofthehighalpineresearchstationjungfraujoch3580masl AT crhoyle sensitivityestimationsforclouddropletformationinthevicinityofthehighalpineresearchstationjungfraujoch3580masl |