B. Croft 1 , R. V. Martin 1,2 , W. R. Leaitch 3 , P. Tunved 4 , T. J. Breider 5 , S. D. D’Andrea 6 , and J. R. Pierce 6,1
1 Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada
2 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA
3 Science and Technology Branch, Environment Canada, Toronto, ON, Canada
4 Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, Sweden
5 School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
6 Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA
AAAR 34 th Annual Conference, Minneapolis, Minnesota
Session 1.RA Remote and Regional Aerosols I
October 13, 2015

Strong Seasonal Cycle in Aerosol Number and Size at High-Arctic Sites
___
Alert
___
Zeppelin
Data from
2011-2013
Alert, Nunavut,
Canada: SMPS
Zeppelin,
Svalbard,
Norway: DMPS
20 50 100 500 20 50 100 500 20 50 100 500 20 50 100
D p
[nm] D p
[nm] ] D p
[nm] ] D p
[nm]
500
Alert
Zeppelin

Alert and Zeppelin Are Similar Despite Their Geographic Separation
150
100
50
0
300
250
200
Total Number Concentration [cm -3 ] Effective diameter [nm]
300
280
260
240
220
200
180
140
120
J F M A M J J A S O N D
Total number maxima in spring and summer
J F M A M J J A S O N D
Q. What processes control these seasonal cycles?
Effective diameter minima in summer

GEOS-Chem-TOMAS Model is Used to Interpret the Observed Cycle
GEOS-Chem-TOMAS with ternary nucleation scheme

GEOS-Chem-TOMAS Model is Used to Interpret the Observed Cycle
GEOS-Chem-TOMAS with ternary nucleation scheme

GEOS-Chem-TOMAS Model is Used to Interpret the Observed Cycle
GEOS-Chem-TOMAS with ternary nucleation scheme

GEOS-Chem-TOMAS Model is Used to Interpret the Observed Cycle
GEOS-Chem-TOMAS with ternary nucleation scheme

GEOS-Chem-TOMAS Model is Used to Interpret the Observed Cycle
GEOS-Chem-TOMAS with ternary nucleation scheme

Key Processes: Wet Removal, Coagulation and New-particle Formation
Alert, Nunavut, Canada

Key Processes: Wet Removal, Coagulation and New-particle Formation
Alert, Nunavut, Canada

Key Processes: Wet Removal, Coagulation and New-particle Formation
Alert, Nunavut, Canada
Wet removal reduces summertime accumulation mode

Key Processes: Wet Removal, Coagulation and New-particle Formation
Alert, Nunavut, Canada
Interstitial coagulation in clouds reduces nonsummer
Aitken mode
Wet removal reduces summertime accumulation mode

Key Processes: Wet Removal, Coagulation and New-particle Formation
Alert, Nunavut, Canada
Interstitial coagulation in clouds reduces nonsummer
Aitken mode
Wet removal reduces summertime accumulation mode

Effective Diameter Seasonal Cycle Occurs Throughout the Arctic
DJF MAM
GEOS-Chem-TOMAS simulation
NEWSCAV+COAG
Stars: Measurement values
JJA
Surface Layer
Effective Diameter [nm]
SON
Alert
Zeppelin

Seasonal Cycles of Number Process Rates for Entire Arctic Troposphere
Nucleation Aitken
Accumulation
Number budgets for
GEOS-Chem-TOMAS simulation
NEWSCAV+COAG
Coarse

Seasonal Cycles of Number Process Rates for Entire Arctic Troposphere
Nucleation Aitken
New-Particle
Formation
Coagulation
Accumulation Coarse
Number budgets for
GEOS-Chem-TOMAS simulation
NEWSCAV+COAG

Seasonal Cycles of Number Process Rates for Entire Arctic Troposphere
Nucleation Aitken
New-Particle
Formation
Transport
Coagulation
Accumulation Coarse
Number budgets for
GEOS-Chem-TOMAS simulation
NEWSCAV+COAG

Seasonal Cycles of Number Process Rates for Entire Arctic Troposphere
Nucleation Aitken
New-Particle
Formation
Transport
Coagulation
Condensation and Transport
Accumulation Coarse
Number budgets for
GEOS-Chem-TOMAS simulation
NEWSCAV+COAG
Wet removal by precipitation

Seasonal Cycles of Number Process Rates for Entire Arctic Troposphere
Nucleation Aitken
New-Particle
Formation
Transport
Coagulation
Condensation and Transport
Accumulation Coarse
Transport and
Emissions
Number budgets for
GEOS-Chem-TOMAS simulation
NEWSCAV+COAG
Wet removal by precipitation

In Summertime Transport Diminishes, Yet Has Non-Negligible Role
Nucleation Size (D p
< 10 nm) Aitken Size (10 nm < D p
< 100 nm)
Transport weakens in spring to summer transition
Accumulation (0.1 μm <D p
< 1 μm ) Coarse Size (D p
> 1 μm )
GEOS-Chem-TOMAS simulation NEWSCAV+COAG

Wet Removal Efficiency Has Stronger Seasonal Cycle in Polar Regions
Spring =>
Summer:
More efficient wet removal reduces lifetime at 1.5-4 km, altitude of
Arctic haze layer
North of 78 °N North of 66 °N North of 50 °N Global
Spring-summer change in wet deposition lifetime is stronger than transport change.
GEOS-Chem simulation NEWSCAV+COAG

• Arctic aerosol number and size => strong, similar seasonal cycle at Alert, Nunavut and Zeppelin, Svalbard.
• Total number maxima: spring (Accumulation mode) and summer (Aitken mode).
• Effective diameter minimum: summer (180 nm), maximum: winter (260 nm).
• GEOS-Chem-TOMAS => Arctic summer: more efficient wet removal, ongoing northward transport, accumulation mode number erodes, promotes new-particle formation.
• Coagulation in clouds reduces Aitken number in non-summer.
• Summertime Arctic aerosol controlled by natural, regional emissions, which have poorly understood effects related to clouds and climate (Poster 8CC.2, Aerosols,
Clouds, & Climate, Thursday PM).

Zeppelin, Svalbard

Zeppelin, Svalbard

Alert

North of 78N

North of 50N

Global