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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

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Tim e

15:00:00 15:20:00 15:40:00 16:00:00 16:20:00 16:40:00 17:00:005

10

15

20

25

30

35

40

45

0.1 1 10 100

C LA C E -2 Jungfrau joch 14 /07 /2002 A M S E vent #3

Run 3: An example of a bimodal cloud droplet spectrum

•Little sulphate mass activated below 400 nm

•Considerable activated sulphate mass activated around 600 to 1000 nm

•Bimodal mass distribution peak at 300 nm and 600 nm.

•Organic and nitrate material activated at 400 nm and below

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CLACE-2

Diameter Dp (µm)

0 10 20 30 40 50

dN/d

logD

p (c

m-3

µm

-1)

0

1000

2000

3000

4000 Event 4 Event 1 Event 2 Event 3

Bimodality in the cloud droplet spectrum:

High droplet numbers with a mean droplet diameter of around 10 um are found when substantial aerosol mass loadings are present.

A larger mode is also sometimes observed, usually associated with a sulphate mass mode at around 600 nm.

MetekHeated Sonic

TSI-AerometricsPDPA

ADA-100DMT FSSP-100

Microphysics Instrumentation

Sphinx Laboratory also operates a PVM for long termmonitoring & lidar dome activation on the

other side of the main dome

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Jungfraujoch 13/07/02 15:45

0

20

40

60

80

100

120

0 10 20 30 40 50 60

Diameter (µm)

Cou

nt

DMT FSSP-100

PDPA TSI

Jungfraujoch 13/07/02 11:58

0

50

100

150

200

250

300

0 10 20 30 40 50 60

Diameter (µm)

Cou

nt

DMT FSSP-100

PDPA TSI

CLACE-2 Jungfraujoch 13/07/2002 PDPA-FSSP Inter-comparison

Mode diameter comparison is within error limits of FSSP

Jungfraujoch 13/07/02 10:18

01020304050

60708090

100

0 10 20 30 40 50 60Diameter (µm)

Cou

nt

0

2345

6789DMT FSSP-100

PDPA TSI

Jungfraujoch 13/07/02 15:45

0

20

40

60

80

100

120

0 10 20 30 40 50 60

Diameter (µm)

Cou

nt

DMT FSSP-100

PDPA TSI

Jungfraujoch 13/07/02 11:58

0

50

100

150

200

250

300

0 10 20 30 40 50 60

Diameter (µm)

Cou

nt

DMT FSSP-100

PDPA TSI

CLACE-2 Jungfraujoch 13/07/2002 PDPA-FSSP Inter-comparison

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.