Cloud Studies with the Droplet Aerosol Analyzer
Author
Summary, in English
Climate change and atmospheric aerosols are a threat for human health and life.
Reducing aerosol emissions would save human lives close to the aerosol source,
but could lead to more death due to the implications of a warmer climate. Aerosol
particles acting as cloud or ice nuclei can induce a change in cloud properties
and thus indirectly induce a change in planetary albedo, which is considered the
major reason of changes in planetary albedo associated with global warming.
Because of the complexity of the interaction between aerosols and clouds,
uncertainties in cloud parametrization remain the major cause of discrepancies
between cloud observations and simulations. Thus, improving the understanding
of aerosol-cloud-interactions is one of the keys for reducing uncertainty in
the estimate of the total anthropogenic radiative forcing and climate sensitivity.
Climate sensitivity is important for quantifying risks and probabilities, and the
development of adaption strategies.
The Droplet Aerosol Analyzer (DAA) was developed to study aerosol-cloud
interaction and is unique in providing the number and the direct relationship
between cloud droplet and residual particle size. For this purpose a more automatic
version with better time resolution (10 min) and an improved and more
automated inversion algorithm has been developed to better suit the needs of
long-term measurements.
Between June and October 2010 aerosol-cloud interaction measurements have
been performed at the summit of Mt. Brocken (51.80 N, 10.62 E, 1142 m a.s.l.)
in central Germany. For this period the aerosol and cloud properties and the
droplet activation regime regarding the ratio between updraft velocity and particle
number concentration (w=Ntot), have been determined.
The relation between cloud droplet number concentration Nd;tot and total
number concentration Ntot, updraft velocity wpred, and size distribution shape
R_0.1um has been determined for three overlapping w=Ntot-intervals.
As expected, for increasing w=Ntot-ratio (from the transitional regime towards
aerosol limited regime) the relative sensitivity ofNd;tot against w decreases while
the relative sensitivity of Nd;tot against Ntot increases. The influence of the size
distribution shape R_0.1um was examined and the absolute relative sensitivity of
Nd;tot against R_0.1um was observed to decrease from the transitional towards the
aerosol limited regime.
The onset of ’roll-off’, where an increase in Ntot does not lead to a proportional
increase in Nd;tot, shifted towards higher total number concentration for
increasing w=Ntot-ratio.
Reducing aerosol emissions would save human lives close to the aerosol source,
but could lead to more death due to the implications of a warmer climate. Aerosol
particles acting as cloud or ice nuclei can induce a change in cloud properties
and thus indirectly induce a change in planetary albedo, which is considered the
major reason of changes in planetary albedo associated with global warming.
Because of the complexity of the interaction between aerosols and clouds,
uncertainties in cloud parametrization remain the major cause of discrepancies
between cloud observations and simulations. Thus, improving the understanding
of aerosol-cloud-interactions is one of the keys for reducing uncertainty in
the estimate of the total anthropogenic radiative forcing and climate sensitivity.
Climate sensitivity is important for quantifying risks and probabilities, and the
development of adaption strategies.
The Droplet Aerosol Analyzer (DAA) was developed to study aerosol-cloud
interaction and is unique in providing the number and the direct relationship
between cloud droplet and residual particle size. For this purpose a more automatic
version with better time resolution (10 min) and an improved and more
automated inversion algorithm has been developed to better suit the needs of
long-term measurements.
Between June and October 2010 aerosol-cloud interaction measurements have
been performed at the summit of Mt. Brocken (51.80 N, 10.62 E, 1142 m a.s.l.)
in central Germany. For this period the aerosol and cloud properties and the
droplet activation regime regarding the ratio between updraft velocity and particle
number concentration (w=Ntot), have been determined.
The relation between cloud droplet number concentration Nd;tot and total
number concentration Ntot, updraft velocity wpred, and size distribution shape
R_0.1um has been determined for three overlapping w=Ntot-intervals.
As expected, for increasing w=Ntot-ratio (from the transitional regime towards
aerosol limited regime) the relative sensitivity ofNd;tot against w decreases while
the relative sensitivity of Nd;tot against Ntot increases. The influence of the size
distribution shape R_0.1um was examined and the absolute relative sensitivity of
Nd;tot against R_0.1um was observed to decrease from the transitional towards the
aerosol limited regime.
The onset of ’roll-off’, where an increase in Ntot does not lead to a proportional
increase in Nd;tot, shifted towards higher total number concentration for
increasing w=Ntot-ratio.
Department/s
Publishing year
2015
Language
English
Full text
- Available as PDF - 37 MB
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Document type
Dissertation
Publisher
Division of Nuclear Physics
Topic
- Earth and Related Environmental Sciences
Keywords
- Cloud
- Aerosol
- DAA
Status
Published
Research group
- Aerosol, Nuclear Physics
Supervisor
- Göran Frank
- Birgitta Svenningsson
- Staffan Sjögren
- Bengt Martinsson
ISBN/ISSN/Other
- ISBN: 978-91-7623-485-3
Defence date
13 November 2015
Defence time
09:00
Defence place
Rydberg Hall, Department of Physics, Sölvegatan 14C, Lund University Faculty of Engineering, Lund
Opponent
- Annele Virtanan (Dr.)