1.4803366.pdf

Observed aerosol effects on marine cloud nucleation and supersaturation

Lynn M. Russell, Armin Sorooshian, John H. Seinfeld, Bruce A. Albrecht, Athanasios Nenes, W. Richard Leaitch

, Anne Marie Macdonald, Lars Ahlm, Yi-Chun Chen, Matthew Coggon, Ashley Corrigan, Jill S. Craven, Richard

C. Flagan, Amanda A. Frossard, Lelia N. Hawkins, Haflidi Jonsson, Eunsil Jung, Jack J. Lin, Andrew R. Metcalf,

Robin Modini, Johannes Mülmenstädt, Greg C. Roberts, Taylor Shingler, Siwon Song, Zhen Wang, and Anna

Wonaschütz

Citation: AIP Conference Proceedings

1527

, 696 (2013); doi: 10.1063/1.4803366

View online: http://dx.doi.org/10.1063/1.4803366

View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1527?ver=pdfcov

Published by the AIP Publishing

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Observed

Aerosol

Effects on Marine

Cloud

Nucleation and Supersaturation

Lynn M. Russell

, Armin Sorooshian

, John H. Seinfeld

, Bruce A. Albrecht

Athanasios Nenes

W. Richard Leaitch

, Anne Marie Macdonald

Lars Ahlm

, Yi

Chun Chen

, Matthew Coggon

Ashley Corrigan

, Jill S. Craven

, Richard C. Flagan

Amanda A. Frossard

Lelia N. Hawkins

Haflidi Jonsson

, Eunsil Jung

, Jack J. Lin

Andrew R. Metcalf

, Robin Modini

, Johannes Mülmenstädt

, Greg C. Roberts

Taylor Shingler

, Siwon Song

, Zhe

n Wang

, Anna Wonaschütz

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA.

California Institute of Technology, Pasadena, CA.

Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ.

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA.

Rosenstiel School of Marine Sciences, University of Miami, Miami, FL.

Center Interdisciplinary Remotely

Piloted Aerosol Studies, Marina, CA.

Department of Atmospher

ic Sciences, University of Arizona, Tucson, AZ.

Department of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA.

Centre National de la Recherche Scientifique, Toulouse, France.

Now at Combustion Research Facility, Sandi

a National Laboratories, Livermore, CA.

Environment Canada, Toronto, Canada.

Harvey Mudd College, Claremont, CA.

Abstract.

Aerosol particles in the marine boundary layer include primary organic and salt

particles from sea spray and combustion

derived par

ticles from ships and coastal cities. These

particle types serve as nuclei for marine cloud droplet activation, although the particles that

activate depend on the particle size and composition as well as the supersaturation that results

from cloud updraft

velocities

. The Eastern Pacific Emitted Aerosol Cloud Experiment (E

PEACE) 2011 was a targeted aircraft campaign

to assess how different particle types nucleate

cloud droplets. As part of E

PEACE 2011, we studied the role of marine particles as cloud

drop

let nuclei and used

emitted particle sources to separate particle

induced feedbacks from

ynamical variability. The emitted particle sources included

shipboard smoke

generated

particles with 0.05

1 μm diameters (which produced tracks measured by satellite

and had drop

composition charac

teristic of organic smoke) and

combustion particles from container ships with

0.05

0.2 μm diameters (which were measured in a variety of conditions with droplets containing

both org

anic and sulfate components)

[1]

. Three central aspects of the collaborative E

PEACE

results are: (1) the size and chemical composition of the emitted smoke particles compared to

ship

track

forming cargo ship emissions as well as backg

round marine particles, with particular

attention to the role of organic particles, (2) the characteristics of cloud track formation for

smoke and cargo ships, as well as the role of multi

layered low clouds, and (3) the implications

of these findings for

quantifying aerosol indirect effects. For comparison with the E

PEACE

results, the preliminary results of the Stratocumulus Observations of Los

Angeles Emissions

Derived Aerosol

Droplets (SOLEDAD) 2012 provided evidence of the cloud

nucleating roles of

th marine organic particles and coastal urban pollution, with simultaneous measurements of

the effective supersaturations of the clouds in the California coastal region. .

Nucleation and Atmospheric Aerosols

AIP Conf. Proc. 1527, 696-701 (2013); doi: 10.1063/1.4803366

696

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Keywords:

Atmospheric Aerosol, Marine Aerosol, Cl

oud Properties, Aerosol

Cloud

Interactions, Marine Boundary Layer.

PACS:

92.60.Mt, 92.60.Nv.

EASTERN PACIFIC EMIT

TED AEROSOL CLOUD

EXPERIMENT (E

PEACE) 2011

PEACE combined a targeted aircraft campaign off the coast of Monterey,

California, in July and A

ugust 2011, with embedded ship

(Fig.

and satellite

observations and modeling studies. Atmospheric conditions in the northeastern Pacific

during July are ideal for formation of homogeneous layers of persistent stratocumulus

clouds. The layers observed h

ave consistent diurnal characteristics, cloud thicknesses

of 100 to 300 m, and cloud top heights typically below 500 m. We employed the R/V

Point Sur

to measure the aerosol below cloud and as a platform for well

characterized

smoke emissions to produce a

uniquely identifiable cloud signature. The Center for

Interdisciplinary Remotely

Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft was

used with a full

payload of instruments

to measure particle and clou

d number, mass,

and composition.

FIGURE

R/V

Point Sur

from the CIRPAS Twin Otter during E

PEACE 2011, showing the

persistence of the plume of smoke generated on the ship in the atmosphere and some of the aircraft

instruments for

measuring particles and clouds (Photo

graph modified from Russell et al.

[1]

The Twin Otter aircraft flew into

clouds behind the emissions from ships

. Figure

shows

one example of measurements of

the number of particles below

cloud and

droplets in cloud, and the pie graphs show that these droplets were almost entirely

organic components with trace amounts of sulfate. The measured ship and marine

characteristics of the organic components during E

PEACE were used to quantify th

widespread contributions of ship emissions to the marine boundary layer aerosol

[2]

The counterflow virtual impactor (CVI) was used as an inlet for evaporating droplets

as they were b

rought into the aircraft, allowing sampling of droplet chemical

composition

[3]

The large organic fraction in Fig.

A is characteristic of smoke

emitted from the generators on the R/V

Point Sur

and contrasts with the composition

697

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of droplets in the cloud not affected by t

he smoke (Fig.

C), which are made up of

three

quarters sulfate and

few

organic components.

FIGURE 2.

Examples of particle and droplet number distributions and mass

based non

refractory

chemical composition, from measurements below (bottom panel) and i

n (top panel) cloud, for the

smoke generator on the R/V

Point Sur

on 16 July (

panel A) and for the stack emissions of a c

argo ship

on 10 August (

panel B). The background particle and droplet concentrations are shown for

16 July and

10 August (

panels C and

D, respectively). The size distributions are plotted at the measured relative

humidity, wet for s

upermicron droplets in cloud (triangles

: 3

μ

m < CDP < 50

μ

m for 16 July and 1

μ

m < CAS < 50

μ

m for 10 August), with passive heating for submicron particle

s in (in

terstitial) and

below cloud (triangles

down

: 0.1

μ

m < PCASP < 2

μ

m), and dried below cloud (diamonds

: 0.01

μ

m <

Scanning DMA < 0.9

μ

m). The pies show composition of the droplets in cloud measured by AMS for

submicron particles below cloud (bottom p

anel) and for the residuals of cloud droplets (top panel) that

are left after drying in a counterflow virtual impactor (11

μ

m < CVI), with

light grey for

organi

components and dark grey for

sulfate). Refractory chemical components (such as Sea Salt) were

not

measured behind the CVI and are not included in the pie graphs. The measurements were collected on

the CIRPAS Twin Otter on 10 August for the cargo ship (1651

1831) and 16 July for the smoke

generators (1704

1801)

. (Reproduc

ed from Russell et al.

[2]

sed with permission

American

Meteorological

Society

)

698

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It is interesting that the background cloud droplets also have 10

30% organic

components. Since the organic composition

outside of

the smoke and ship plumes was

very similar to characteristic organic functional groups associated with marine sources

[4]

, it is likely that this organic fraction was of marine origin. The presence of a

similar organic fraction in the droplet residuals shows that this organic mass also acted

as CCN in nucleating

cloud drops.

To understand the differences in the two days shown in Fig. 2, we compared the

measured updraft velocity and estimated the maximum supersaturation by comparing

the cloud drop number (CDN) concentration with the cloud condensation nuclei

(CCN)

spectra. The results for the two days are given in Table 1, which is taken from

Russell et al.

[1]

While there is uncertainty in using the maximum supersaturation

calculated from the measur

ed average CDN and the CCN spectra, the calculated

updraft velocities were consistent with the measured maximum updraft velocities (in

cloud) of 0.94 m s

(respectively) on 16 July and

1.2 m s

(respectively) on 10

Aug

ust.

TABLE

Particle and droplet characteristics for below and in

cloud measurements shown in Fig. 2.

Measured Maximum Updraft

Velocity [m s

]

Calculated Maximum

Supersaturation [%]

16 July 2011 (generator smoke)

0.94

0.09

10 August 2011 (cargo ship)

1.22

0.25

STRATOCUMULUS OBSERV

ATIONS OF LOS

ANGELES

EMISSIONS DERIVED AE

ROSOL

DROPLETS (SOLEDAD) 2

012

Stratocumulus Observations of Los

Angeles Emissions Derived Aerosol

Droplets

(SOLEDAD) 2012 took place during May and June in La Jolla, California. Aerosol

parti

cles were sampled at Scripps pier and at the peak of Mount Soledad, 1.5 mi from

the pier sampling location and 250 m above sea level. Stratocumulus clouds were

observed frequently at levels between 100 and 500 m, and there were several

nighttime cloud lay

ers during which the mountaintop site was in cloud. One such

event is shown in Fig. 3. These events tended to be characterized by onshore winds

and CDN concentrations below 100 cm

, suggesting that the clouds were similar to

the marine stratocumulus sam

pled during E

PEACE 2011.

The SOLEDAD 2012 campaign provided the opportunity to measure drop

formation in coastal conditions and to calculate supersaturation by a second method.

In this campaign, several hours of sampling in cloud allowed us to use measur

ements

of CCN concentration behind the counterflow virtual impactor to compare the

measured supersaturation of the droplet residuals to the CDN concentration. With this

approach, we measured a distribution of supersaturations during up to 6 hr of sampling

in each cloud event. The values ranged from below 0.1% to above 0.7%, although

most were below 0.4%. It is possible that the larger supersaturations reflect the

contributions of scavenged components to the droplet composition, but it is also likely

that

this range reflects the variability in updraft velocities.

699

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131.215.71.79 On: Mon, 10 Mar 2014 17:28:35

FIGURE

Instrumented van on Mount Soledad during a stratocumulus cloud measured as part of

SOLEDAD 2012. The picture shows the rotating aerosol inlet, the counterflow virtual impactor, in

cloud spectrometers, and an active

flow cloud water collector.

CLOUD NUCLEATION AND

SUPERSATURATION

For both campaigns, online measurements of non

refractory components in aerosol

particles below cloud and droplet residual in cloud show very similar compo

sitions

–

in other words the similarity of droplet and submicron aerosol composition in multiple

marine stratocumulus cloud events suggests that that the accumulation mode mass is

responsible for most of the nucleating droplets. While some droplet composi

tions will

be changed by scavenging of interstitial particles, the very similar fractions of

different components suggests that the nucleated particles are largely the same as the

submicron particles in composition. A striking example is provided by the dr

residuals composed of generated smoke nuclei, since their composition indicates the

ability of very “fresh” hydrocarbon emissions to nucleate cloud droplets at low

supersaturations with negligible hygroscopic uptake by sulfate.

These results were found

for clouds with a range of supersaturations typical of

marine stratocumulus, from below 0.1% up to 0.4%. We estimated these effective

supersaturations in two ways, both by directly comparing the activated droplet

population to the measured CCN spectra an

d by measuring the CCN spectra of the

700

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droplet residuals. Interestingly, this variability is comparable to the values used to

calculate that in

cloud sulfate formation could contribute to new CCN

[5]

ACKNOWLEDGMENTS

The E

PEACE 2011 field campaign and modeling studies were funded by the

National Science

Foundation (AGS

1013423; AGS

1008848; AGS

1013381; AGS

1013319; ATM

0744636; AGS

0821599; ATM

0349015) and the Office of Naval

Research (N00014

0783; N00014

0811; N00014

0200; N00014

0465). Sea Spray Research, Inc., provided oil for th

e operation of the smoke

generators. The authors gratefully acknowledge the crews of the CIRPAS Twin Otter

and the R/V

Point Sur

for their assistance during the field campaign, Tom Maggard

who revived and tirelessly maintained the smoke generators during t

he cruise, and

Spyros Pandis for providing the CCN spectrometer. The SOLEDAD 2012 field

measurements shown here were a collaboration of Scripps Institution of

Oceanography and Environment Canada.

REFERENCES

L.M. Russell, A. Sorooshian, J.H. Seinfeld, B.A. Albrecht, A. Nenes, L. Ahlm, Y.

C. Chen, M.

Coggon, J.S. Craven, R.C. Flagan, A.A. Frossard, H. Jonsson, E. Jung, J.J. Lin, A.R. Metcalf, R.

Modini, J. Mülmenstädt, G.C. Roberts, T. Shingler, S. Song, Z.

Wang, and A. Wonaschütz, Eastern

Pacific Emitted Aerosol Cloud Experiment (E

Peace),

Bulletin of the American Meteorological

Society

, 10.1175/BAMS

00015 (2013 in press).

M.M. Coggon, A. Sorooshian, Z. Wang, A.R. Metcalf, A.A. Frossard, J.J. Lin,

J.S. Craven, A.

Nenes, H.H. Jonsson, L.M. Russell, R.C. Flagan, and J.H. Seinfeld, Ship Impacts on the Marine

Atmosphere: Insights into the Contribution of Shipping Emissions to the Properties of Marine

Aerosol and Clouds,

Atmospheric Chemistry and Physics

(18), 8439

8458, 10.5194/acp

8439

2012 (2012).

T. Shingler, S. Dey, A. Sorooshian, F.J. Brechtel, Z. Wang, A. Metcalf, M. Coggon, J. Mulmenstadt,

L.M. Russell, H.H. Jonsson, and J.H. Seinfeld, Characterisation and Airborne Deployment of a New

Cou

nterflow Virtual Impactor Inlet,

Atmospheric Measurement Techniques

(6), 1259

1269,

10.5194/amt

1259

2012 (2012).

L.M. Russell, L.N. Hawkins, A.A. Frossard, P.K. Quinn, and T.S. Bates, Carbohydrate

Composition of Submicron Atmospheric Particles

and Their Production from Ocean Bubble

Bursting,

Proceedings of the National Academy of Sciences of the United States of America

107

(15), 6652

6657, 10.1073/pnas.0908905107 (2010).

Y.J. Kaufman and D. Tanre, Effect of Variations in Supersaturation on

the Formation of Cloud

Condensation Nuclei,

Nature

369

(6475), 45

48, 10.1038/369045a0 (1994).

701

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