meteorological service of canada environment canada the global cycling of size- distributed sea-salt...

Meteorological Service of CanadaEnvironment Canada

The Global Cycling Of Size-distributed Sea-salt Particles And

Their Influence On Sulphate Aerosols

Sun Ling Gong1 and Leonard A. Barrie2

1Air Quality Research Branch, Meteorological Service of Canada,

4905 Dufferin Street, Toronto, Ontario M3H 5T4, CANADA2Environment Division, AREP, World Meteorological Organization, 7

bis, Avenue de la Paix, BP2300, 1211 Geneva 2

WMO


CAM: A Size Segregated Simulation of Atmospheric CAM: A Size Segregated Simulation of Atmospheric Aerosol Processes for Climate and Air Quality ModelsAerosol Processes for Climate and Air Quality Models

J. Geophy. Res. 2002 (in press)

1. Module Development

S.L. Gong1, L.A. Barrie2, J.-P. Blanchet3, K. von Salzen5, U. Lohmann4, G. Lesins4, L. Spacek3, L.M. Zhang1, E. Girard3, H. Lin1, R. Leaitch1, H. Leighton5, P. Chylek4 and P. Huang1

2. Global sea-salt aerosol and its budgets S.L. Gong1, L.A. Barrie2 and M. Lazare1


Model Configurations – CAM/GCMModel Configurations – CAM/GCM


Global Sea-salt Global Sea-salt Simulations Simulations and Budgetsand Budgets


0.01 0.02 0.04 0.06 0.08 0.2 0.4 0.6 0.8 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

nmol Na mol-1

Spring - MAM Summer - JJA

Fall - SON Winter - DJF

Global Sea-salt ConcentrationsGlobal Sea-salt Concentrations


Global Global Sea-salt Sea-salt Compared Compared with with ObservationsObservations

0 3 6 9 12 150

3

6

9

12

15

0 3 6 9 12 150

3

6

9

12

15

Observation [nmole Na+ mole-1]

0 3 6 9 12 15

Mo

de

l [n

mo

le N

a+ m

ole

-1]

0

3

6

9

12

15

0 3 6 9 12 150

3

6

9

12

15MAM JJA

SON DJF

Comparison Sites Comparison Sites [WCRP/IGAC COSAM][WCRP/IGAC COSAM]


Sea-salt Size DistributionsSea-salt Size Distributions

(d) Model 197 hPa

(b) Quinn et al. [1996] Surface

(c) Model 698 hPa

(a) Model 995 hPa

0.077 0.135 0.271 0.542 1.085 2.17 4.34

-67

-

65

-59

-39

-20

-13

7

27

48

Latit

ude

Dp , m

RITS 93, Na +

g/m /dlogD3p

> 1.2

0.9 - 1.2

0.6 - 0.9

0.3 - 0.6

< 0.3

Compare


(a) Size bin 11 (r=5.12-10.24 m)

Residence Time (hour)

Global Sea-salt Residence Times - CoarseGlobal Sea-salt Residence Times - Coarse


Global Sea-salt Residence Times - FineGlobal Sea-salt Residence Times - Fine(b) Size bin 7 (r=0.32-0.64 m)

Residence Time (hour)


O c e a n La nd

Atm o sp he re1

0.1

31.4

4%

(N

H)

31.7

4%

(N

H)

31.0

0%

(N

H)

34.5

5%

(N

H)

51.1

0%

(N

H)

49.7

7%

(N

H)

60.3

1%

(N

H)

9.2

7

0.1

28

~ 0 .15

0.0

05

0.1

57

0.5

56

0.0

17

F lux D ry D ep B elow - in -C loud

R un-o ff

Annual Global Sea-salt Budgets Annual Global Sea-salt Budgets

×1012 kggiga-ton


Month

1 2 3 4 5 6 7 8 9 10 11 12

Glo

ba

l Mo

nth

ly E

mis

sio

n,

Kg

2.00x1010

2.20x1011

4.20x1011

6.20x1011

8.20x1011

1.02x1012

No

rth

ern

He

mis

ph

ere

Pe

rce

nta

ge

15

20

25

30

35

40

45

50

Monthly Total Emission

Southern HemisphereEmission

Northern HemisphereEmission

Norhtern Percentage

Global Monthly Sea-salt EmissionsGlobal Monthly Sea-salt Emissions


Global Sulphate Global Sulphate Aerosols Aerosols

Influenced by Influenced by Sea-saltSea-salt


M AM

SON DJF

JJA

0.01 0.02 0.04 0.06 0.08 0.1 0.3 0.6 0.8 1.0 1.5 2.0 2.5 3.0

Nm ole SO mole4

2- -1

Global Sulphate ConcentrationsGlobal Sulphate Concentrations


0 1 20

1

2

0 1 20

1

2

Observation [nmole SO42- mole-1]

0 1 2

Mo

de

l [n

mo

le S

O 42

- mo

le-1

]

0

1

2

0 1 20

1

2MAM JJA

SON DJF

Global Global Sulphate Sulphate Compared Compared with with ObservationsObservations

Comparison Sites Comparison Sites [WCRP/IGAC COSAM][WCRP/IGAC COSAM]


Total (SS+SF) Volume Size Distribution

D, m

0.01 0.1 1 10

dV

/dlo

gD

,m

3 c

m-3

10-4

10-3

10-2

10-1

100

101

Volume Size DistributionsVolume Size Distributions

Quinn et al. 1996Quinn et al. 1996SimulationsSimulations

140W, 40S140W, 40S


Global Sulphate DistributionsGlobal Sulphate Distributions

0.01 0.02 0.04 0.06 0.08 0.1 0.3 0.6 0.8 1.0 1.5 2.0 2.5 3.0

Nmole SO mole4

2- -1

DJF

Without Sea-salt With Sea-salt


-0.3 -0.2 -0 .1 0. 0.1 0.2 0.3 0.4 0.5 0.6 0.7

MAM JJA

SON DJF

Fraction

Surface Reduction of Sulphate by Sea-saltSurface Reduction of Sulphate by Sea-salt

-20~30%

-50~70%

-20~30%

Rosenfeld et al 2002, Science“Sea-salt cleans air pollution”

-10~20%


Mechanisms of the Sea-salt Impact – (1)Mechanisms of the Sea-salt Impact – (1)

Cleaning Agents– Condensation of sulphuric acid vapour

onto existing sea-salt particles reduces the atmospheric sulphate cycling time and hence reduces the sulphate concentrations.

– Sea-salt aerosols override the precipitation suppression effects of the large number of small pollution nuclei.


C a s e A

( a 1 ) 4 0 ° N S u l p h a t e N u m b e r S i z e D i s t r i b u t i o n

0 . 0 1 0 . 1

dN

/dlo

gD

, c

m-3

0

1 0 0

2 0 0

3 0 0

4 0 0

5 0 0

6 0 0

C a s e B ( b 1 ) 4 0 ° N S u l p h a t e N u m b e r S i z e D i s t r i b u t i o n

0 . 0 1 0 . 1

dN

/dlo

gD

, c

m-3

0

1 0 0

2 0 0

3 0 0

4 0 0

5 0 0

6 0 0

( a 2 ) 0 °

S u l p h a t e N u m b e r S i z e D i s t r i b u t i o n

0 . 0 1 0 . 1

dN

/dlo

gD

, c

m-3

0

1 0 0

2 0 0

3 0 0

( b 2 ) 0 ° S u l p h a t e N u m b e r S i z e D i s t r i b u t i o n

0 . 0 1 0 . 1

dN

/dlo

gD

, c

m-3

0

1 0 0

2 0 0

3 0 0

dN

/dlo

gD

, c

m-3

( a 3 ) 4 0 ° S S u l p h a t e N u m b e r S i z e D i s t r i b u t i o n

0 . 0 1 0 . 1

dN

/dlo

gD

, c

m-3

0

5 0

1 0 0

1 5 0

2 0 0

( b 3 ) 4 0 ° S S u l p h a t e N u m b e r S i z e D i s t r i b u t i o n

0 . 0 1 0 . 1

dN

/dlo

gD

, c

m-3

0

5 0

1 0 0

1 5 0

2 0 0

D , m

dN

/dlo

gD

, c

m-3

Impact of Sea-Impact of Sea-salt on salt on Sulphate Sulphate Number Size Number Size Distributions Distributions

Sea-salt reduces the number concentration of sulphate by enhancing condensation and coagulations.


0. 0 .1 0 .2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 m

Case B (w ith sea-salt)Case A (no sea-salt)

Mass-mean Diameters of Sulphate (MAM)Mass-mean Diameters of Sulphate (MAM)

Increases in MMD reduce the residence time and hence concentrations of sulphate.


Mechanisms of the Sea-salt Impact – (2)Mechanisms of the Sea-salt Impact – (2)

Effects on Clouds– Sea-salt provides additional CCN for SO2 in-

cloud oxidation and hence increases the sulphate concentrations.

– An increase more than 20% in in-cloud sulphate production due to additional sea-salt particles and higher pH associated with newly formed sea-salt-nucleated cloud droplets compared to sulphate. [O’Dowd et al. 1997, Lowe et al. 1995]


Sea-salt on cloud droplet numberSea-salt on cloud droplet number

[Pszenny et al 1998][Pszenny et al 1998][O’Dowd et al. 1999][O’Dowd et al. 1999][Rosenfeld et al 2002]

Sea-salt aerosols override the precipitation suppression effects of the large number of small pollution nuclei.

The enhancement in precipitation helps remove pollution.


-0.3 -0.2 -0 .1 0. 0.1 0.2 0.3 0.4 0.5 0.6 0.7

MAM JJA

SON DJF

Fraction

Changes of Sulphate MMR by Sea-saltChanges of Sulphate MMR by Sea-salt

10~20%

Competitive processes of sea-salt with positive and negative effects on sulphate.

Location dependent.


ConclusionsConclusions

The global annual sea-salt emission to the atmosphere is about 1.01×1013 kg with 68% in the southern hemisphere.

Residence times of 7.7 m and 0.4 m diameter sea salt particles in the marine boundary layer were in the range 0.3 - 10 hours and 80 – 360 hours, respectively.

By serving as a quenching agent to nucleation and additional surface area for condensation, sea-salt aerosols increase the mass mean diameter of sulphate aerosols by a factor of 2 and reduce the global sulphate aerosol mass in the surface MBL layer from 5 to 75% for most of the open oceans.

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