Download presentation
Presentation is loading. Please wait.
1
Processes Controlling Arctic Aerosol Number and Size: Seabird-Climate Connections
B. Croft1, R. V. Martin1,2, G. R. Wentworth3, W. R. Leaitch4, J. G. Murphy3, J. Kodros5, P. Tunved6, T. J. Breider7, S. D. D’Andrea5, J. P. D. Abbatt3 and J. R. Pierce5,1 1Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada 2Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA 3Science and Technology Branch, Environment Canada, Toronto, ON, Canada 4Department of Chemistry, University of Toronto, Toronto, ON, Canada 5Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA 6Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, Sweden 7School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA NETCARE 2015 Workshop University of Toronto, Toronto, Canada November 16, 2015
2
Strong Seasonal Cycle in Aerosol Number and Size at High-Arctic Sites
___ Data from Alert, Nunavut, Canada: SMPS Zeppelin, Svalbard, Norway: DMPS Alert ___ Zeppelin dN/dlogDp [cm-3] dN/dlogDp [cm-3] dN/dlogDp [cm-3] Alert Zeppelin What are the controlling processes? Dp [nm] Dp [nm] ] Dp [nm] ] Dp [nm]
3
Observed Seasonal Mean Aerosol Size Distributions
Alert, Nunavut, Canada
4
GEOS-Chem-TOMAS Model is Used to Interpret the Observed Cycle
Alert, Nunavut, Canada
5
Key Processes: Wet Removal
Alert, Nunavut, Canada Wet removal reduces summertime accumulation mode
6
Key Processes: Wet Removal, Coagulation
Alert, Nunavut, Canada Interstitial coagulation in clouds reduces non-summer Aitken mode Wet removal reduces summertime accumulation mode
7
Key Processes: Wet Removal, Coagulation and New-particle Formation
Alert, Nunavut, Canada Interstitial coagulation in clouds reduces non-summer Aitken mode Wet removal reduces summertime accumulation mode
8
Seasonal Cycles of Number Process Rates for Entire Arctic Troposphere
Nucleation Dp < 10 nm Aitken 10 < Dp < 100 nm Accumulation Dp > 1000 nm Coarse Number budgets for GEOS-Chem-TOMAS simulation NEWSCAV+COAG 100 < Dp < 1000 nm
9
Seasonal Cycles of Number Process Rates for Entire Arctic Troposphere
Nucleation Dp < 10 nm Aitken 10 < Dp < 100 nm New-Particle Formation Coagulation Accumulation Dp > 1000 nm Coarse Number budgets for GEOS-Chem-TOMAS simulation NEWSCAV+COAG 100 < Dp < 1000 nm
10
Seasonal Cycles of Number Process Rates for Entire Arctic Troposphere
Nucleation Dp < 10 nm Aitken 10 < Dp < 100 nm New-Particle Formation Transport Coagulation Accumulation Dp > 1000 nm Coarse Number budgets for GEOS-Chem-TOMAS simulation NEWSCAV+COAG 100 < Dp < 1000 nm
11
Seasonal Cycles of Number Process Rates for Entire Arctic Troposphere
Nucleation Dp < 10 nm Aitken 10 < Dp < 100 nm New-Particle Formation Transport Coagulation Accumulation Dp > 1000 nm Coarse Condensation and Transport Number budgets for GEOS-Chem-TOMAS simulation NEWSCAV+COAG Wet removal by precipitation
12
Seasonal Cycles of Number Process Rates for Entire Arctic Troposphere
Nucleation Dp < 10 nm Aitken 10 < Dp < 100 nm New-Particle Formation Transport Coagulation Transport and Emissions Accumulation Coarse Condensation and Transport Number budgets for GEOS-Chem-TOMAS simulation NEWSCAV+COAG Dp > 1000 nm Wet removal by precipitation
13
Particle Precursors: Arctic Seabirds Emit Ammonia of ~ 50 Gg yr-1
1. Gas production Guano + H2O + O2 --> NH3(g) 2. Particle production NH3(g) + H2SO4(g) + H2O(g) --> new particles Circles: Riddick et al., 2012 inventory Stars: Added emissions from Circumpolar Seabird Data Portal [Mg NH3 yr-1 colony-1]
14
Seabird Colony Emissions Strongly Control Free NH3 In Arctic
Change in Summertime Mean Surface Layer NH3(g)+NH4+(s) With Seabird Colony NH3 Emissions in GEOS-Chem-TOMAS Model Climate relevant impacts Increased new-particle formation More numerous cloud condensation nuclei following particle growth Clouds with greater reflectivity of solar radiation [%]
15
Sufficient NH3 to Simulate Bursts of New-Particle Formation at Alert
Aerosol Number with Dp > 10 nm from CPC
16
Seabird Colony NH3 Sufficient to Control Alert Aerosol Neutralization
17
New Particles Grow to Sizes that Change Cloud Droplet Number
18
Pan-Arctic Aerosol Indirect Effect from Seabird Colony NH3: -0.3 Wm-2
For same liquid water content, clouds with more and smaller cloud droplets are brighter --> cooling.
19
Summary and Outlook Thanks! Questions ??
Pan-Arctic aerosol number and size have a strong seasonal cycle. Key processes in Arctic summer: more efficient wet removal, ongoing northward transport, accumulation mode number erodes, promotes new-particle formation. GEOS-Chem-TOMAS indicates that Arctic seabird NH3 emissions yield sufficient free NH3 to key trigger to new-particle formation. Growth of the seabird-influenced particles modifies Arctic cloud droplet number, yielding pan-Arctic aerosol indirect effect of -0.3 W m-2. Future work: evaluate GEOS-Chem-TOMAS vertical profiles of aerosol number, CCN, IN and related-process representations with NETCARE measurements. Thanks! Questions ??
20
Extra Slides
21
Alert and Zeppelin Are Similar Despite Their Geographic Separation
Total Number Concentration [cm-3] Effective diameter [nm] 300 250 200 150 100 50 300 280 260 240 220 200 180 140 120 J F M A M J J A S O N D J F M A M J J A S O N D Total number maxima in spring and summer Effective diameter minima in summer Q. What processes control these seasonal cycles?
22
GEOS-Chem-TOMAS Model is Used to Interpret the Observed Cycle
Alert, Nunavut, Canada Alert, Nunavut, Canada Alert GEOS-Chem-TOMAS with ternary nucleation scheme
23
Effective Diameter Seasonal Cycle Occurs Throughout the Arctic
DJF MAM GEOS-Chem-TOMAS simulation NEWSCAV+COAG Stars: Measurement values Surface Layer Effective Diameter [nm] JJA SON Alert Zeppelin
24
In Summertime Transport Diminishes, Yet Has Non-Negligible Role
Nucleation Size (Dp < 10 nm) Aitken Size (10 nm < Dp < 100 nm) Transport weakens in spring to summer transition Accumulation (0.1 μm <Dp< 1 μm ) Coarse Size (Dp > 1 μm ) GEOS-Chem-TOMAS simulation NEWSCAV+COAG
25
Wet Removal Efficiency Has Stronger Seasonal Cycle in Polar Regions
More efficient wet removal => shorter number lifetimes at altitude of Arctic haze layer (1.5-4 km) during spring to summer transition. Spring-summer change in wet deposition lifetime is stronger than transport change. GEOS-Chem simulation NEWSCAV+COAG
26
Zeppelin, Svalbard
27
Zeppelin, Svalbard
28
Alert
29
North of 78N
30
North of 50N
31
Global
Similar presentations
