1 Measurements of the size resolved composition of submicron aerosol particles and their interstitial fraction during cloud events at the Jungfraujoch Global Atmospheric Watch Station in the free troposphere of the Swiss Alps H. Coe , J. D. Allan, M. R. Alfarra, P. I. Williams, K. N. Bower, G. McFiggans, M. Flynn, M. W. Gallagher, and T. W. Choularton Physics Department, UMIST, P. O. Box 88, Manchester M60 1QD, UK E. Weingartner, C. Corrigan and U. Baltensperger Paul Scherrer Institute CH-5232 Villigen PSI, Switzerland D. Worsnop Aerodyne Research Inc., 45 Manning Road, Billerica, MA, USA CLACE-2 Aims To use measurement techniques and models of aerosol thermodynamics to make comprehensive predictions of the sub and super saturated water affinity of particles in a wide variety of conditions and test these using further detailed measurements. Measure the chemical composition of boundary layer and free tropospheric air of varying ages at the Jungfraujoch Research Station using an Aerosol Mass Spectrometer at high time and aerosol size resolution. Measure the size dependent composition of total and interstitial aerosol particles during cloud events using twin inlets and infer the composition of particles activated during cloud events. Perform an initial field comparison of cloud droplet spectra measured by a new phase Doppler anemometry system and a Forward Scattering Spectrometer Probe.
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Measurements of the size resolved composition ofsubmicron aerosol particles and their interstitial
fraction during cloud events at the Jungfraujoch Global Atmospheric Watch Station in the free troposphere of
the Swiss Alps
H. Coe , J. D. Allan, M. R. Alfarra, P. I. Williams, K. N. Bower, G.McFiggans, M. Flynn, M. W. Gallagher, and T. W. Choularton
Physics Department, UMIST, P. O. Box 88, Manchester M60 1QD, UK
E. Weingartner, C. Corrigan and U. Baltensperger
Paul Scherrer Institute CH-5232 Villigen PSI, Switzerland
D. Worsnop
Aerodyne Research Inc., 45 Manning Road, Billerica, MA, USA
CLACE-2 Aims
To use measurement techniques and models of aerosol thermodynamics to make comprehensive predictions of the sub and super saturated water affinity of particles in a wide variety of conditions and test these using further detailed measurements.
Measure the chemical composition of boundary layer and free tropospheric air of varying ages at the Jungfraujoch Research Station using an Aerosol Mass Spectrometer at high time and aerosol size resolution.
Measure the size dependent composition of total and interstitial aerosol particles during cloud events using twin inlets and infer the composition of particles activated during cloud events.
Perform an initial field comparison of cloud droplet spectra measured by a new phase Doppler anemometry system and a Forward Scattering Spectrometer Probe.
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Experiment Site:Sphinx Observatory, Jungfraujoch ∼12,000 ft
Microphysics Platform
AerosolInlets:Total &
Interstitial.CPC, OPC
DMPSHTDMA
AMSCarbon
Particle Inlet (1 atm)
100% transmission (60-600 nm), aerodynamic sizing, linear mass signal.Development of an Aerosol Mass Spectrometer for Size and Composition Analysis of SubmicronParticles. Jayne et al., Aerosol Science and Technology 33:1-2(49-70), 2000.
QuadrupoleMass Spectrometer
Thermal Vaporization
&Electron Impact
Ionization
Aerodynamic Lens
(2 Torr)
Chopper
Turbo Pump
Turbo Pump
Turbo Pump
TOF Region
Particle Beam Generation
Aerodynamic Sizing Particle Composition
Aerodyne Aerosol Mass Spectrometer (AMS)
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Example of a mass spectrum from the AMS at the Jungfraujoch
Organics
Sulphate
Nitrate
Ammonium
Data from the Total Inlet
Organics
Sulphate
Nitrate
Ammonium
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Data from the Total Inlet
Organics
Sulphate
Nitrate
Ammonium
Data from the Total Inlet
Organics
Sulphate
Nitrate
Ammonium
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The size distribution of the organic fraction
*The largest contribution to the organic mass is from m/z=44, CO2+.
*Masses arising from oxidised organic fragmentation all have similar size distributions.*There is little contribution to the total organic mass from masses typical of unoxidised aliphatic fragmentation e.g. n/z = 57
Differences between the sample inlets in and out of cloud: Nitrate
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Differences between the sample inlets in and out of cloud: Sulphate
Run 6: An example of an out of cloud size distribution
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Run 6: An example of an out of cloud size distribution
Run 1: An example of high cloud droplet number and low droplet mean radius
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Time
19:00:00 20:00:00 21:00:00 22:00:00
Dia
met
er (µ
m)
5
10
15
20
25
30
35
40
45
0.1 1 10 100
CLACE-2 Jungfraujoch 11/07/2002 AMS Event #1
Run #1: Mass Spectra from the total and interstitial Inlets
Total
Interstitial
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Run 1: An example of high cloud droplet number and low droplet mean radius
•Most sulphate, organic and nitrate activated
•Little sulphate or nitrate activated below 100 nm
•Mass distributions peak at 300 nm, implying large numbers of small particles
•Organic material activated below 100 nm
Run 3: An example of a bimodal cloud droplet spectrum
Mode diameter comparison is within error limits of FSSP
Differences are observed for large mode in bimodal conditions
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SUMMARY
* Free tropospheric mass size distributions of a range of volatiles and semi volatiles have been obtained at the JFJ GAW station
* Organic and SO42- mass loadings are similar and range from 0.1 to 0.6 ug m-3.
* Katabatic flow advects polluted air masses from the PBL during the day, cleaner air is observed during anabatic conditions at night
* Dry residual and interstitial particles discriminated using a dual inlet system.
* In orographically produced cloud a single mode (Dmode~10 um) was observed, generally with a high number concentration during upslope conditions
* Bimodal droplet spectra indicate two activation processes, one associated with the synoptically formed cloud, the other with from local strong updraughts
* Activation of SO42- and NO3
- for particles > 100nm in the high Droplet N case
* Evidence that activation of organic particles below 100nm occurs
* In bimodal case a sulphate mode at large sizes (600 nm) was observed but less sulphate activated in 300 nm mode than organic mass
* A PDPA system showed good agreement with FSSP at small droplet sizes but large droplets were observed by PDPA to be larger than those from FSSP.