scholarly journals Weak sensitivity of cloud condensation nuclei and the aerosol indirect effect to Criegee + SO<sub>2</sub> chemistry

2012 ◽  
Vol 12 (12) ◽  
pp. 33127-33163 ◽  
Author(s):  
J. R. Pierce ◽  
M. J. Evans ◽  
C. E. Scott ◽  
S. D. D'Andrea ◽  
D. K. Farmer ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Indirect Effect ◽  
Ultrafine Particles ◽  
Transport Model ◽  
Cloud Condensation Nuclei ◽  
Chemical Mechanism ◽  
Model Parameters ◽  
Condensation Nuclei ◽  
Aerosol Indirect Effect ◽  
Cloud Albedo

Abstract. H2SO4 vapor is important for the nucleation of atmospheric aerosols and the growth of ultrafine particles to cloud condensation nuclei (CCN) sizes. Recent studies have found that reactions of stabilized Criegee intermediates (CIs, formed from the ozonolysis of alkenes) with SO2 may be an important source of H2SO4 that has been missing from atmospheric aerosol models. In this paper, we use the chemical transport model, GEOS-Chem, with the online aerosol microphysics module, TOMAS, to estimate the possible impact of CIs on present-day H2SO4, CCN, and the cloud-albedo aerosol indirect effect (AIE). We extend the standard GEOS-Chem chemistry with CI-forming reactions (ozonolysis of isoprene, methyl vinyl ketone, methacrolein, propene, and monoterpenes) from the Master Chemical Mechanism. Using a fast rate constant for CI+SO2, we find that the addition of this chemistry increases the global production of H2SO4 by 4%. H2SO4 concentrations increase by over 100% in forested tropical boundary layers and by over 10–25% in forested NH boundary layers (up to 100% in July) due to CI + SO2 chemistry, but the change is generally negligible elsewhere. The predicted changed in CCN were strongly dampened to the CI + SO2 changes in H2SO4 in these regions: less than 15% in tropical forests and less than 2% in most mid-latitude locations. The global-mean CCN change was less than 1% both in the boundary layer and the free troposphere. The associated cloud-albedo AIE change was less than 0.03 W m−2. The model global sensitivity of CCN and the AIE to CI + SO2 chemistry is significantly (approximately one order-of-magnitude) smaller than the sensitivity of CCN and AIE to other uncertain model inputs, such as nucleation mechanisms, primary emissions, SOA and deposition. Similarly, comparisons to size-distribution measurements show that uncertainties in other model parameters dominate model biases in the model-predicted size distributions. We conclude that improvement in the modeled CI + SO2 chemistry would not likely to lead to significant improvements in present-day CCN and AIE predictions.

scholarly journals Weak global sensitivity of cloud condensation nuclei and the aerosol indirect effect to Criegee + SO<sub>2</sub> chemistry

2013 ◽  
Vol 13 (6) ◽  
pp. 3163-3176 ◽  
Author(s):  
J. R. Pierce ◽  
M. J. Evans ◽  
C. E. Scott ◽  
S. D. D'Andrea ◽  
D. K. Farmer ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Indirect Effect ◽  
Cloud Condensation Nuclei ◽  
Chemical Mechanism ◽  
Model Parameters ◽  
Condensation Nuclei ◽  
Aerosol Indirect Effect ◽  
Global Sensitivity ◽  
Cloud Albedo ◽  
The Impact

Abstract. H2SO4 vapor is important for the nucleation of atmospheric aerosols and the growth of ultrafine particles to cloud condensation nuclei (CCN) sizes with important roles in the global aerosol budget and hence planetary radiative forcing. Recent studies have found that reactions of stabilized Criegee intermediates (CIs, formed from the ozonolysis of alkenes) with SO2 may be an important source of H2SO4 that has been missing from atmospheric aerosol models. For the first time in a global model, we investigate the impact of this new source of H2SO4 in the atmosphere. We use the chemical transport model, GEOS-Chem, with the online aerosol microphysics module, TOMAS, to estimate the possible impact of CIs on present-day H2SO4, CCN, and the cloud-albedo aerosol indirect effect (AIE). We extend the standard GEOS-Chem chemistry with CI-forming reactions (ozonolysis of isoprene, methyl vinyl ketone, methacrolein, propene, and monoterpenes) from the Master Chemical Mechanism. Using a fast rate constant for CI+SO2, we find that the addition of this chemistry increases the global production of H2SO4 by 4%. H2SO4 concentrations increase by over 100% in forested tropical boundary layers and by over 10–25% in forested NH boundary layers (up to 100% in July) due to CI+SO2 chemistry, but the change is generally negligible elsewhere. The predicted changes in CCN were strongly dampened to the CI+SO2 changes in H2SO4 in some regions: less than 15% in tropical forests and less than 2% in most mid-latitude locations. The global-mean CCN change was less than 1% both in the boundary layer and the free troposphere. The associated cloud-albedo AIE change was less than 0.03 W m−2. The model global sensitivity of CCN and the AIE to CI+SO2 chemistry is significantly (approximately one order-of-magnitude) smaller than the sensitivity of CCN and AIE to other uncertain model inputs, such as nucleation mechanisms, primary emissions, SOA (secondary organic aerosol) and deposition. Similarly, comparisons to size-distribution measurements show that uncertainties in other model parameters dominate model biases in the model-predicted size distributions. We conclude that improvement in the modeled CI+SO2 chemistry would not likely lead to significant improvements in present-day CCN and AIE predictions.

scholarly journals Global cloud condensation nuclei influenced by carbonaceous combustion aerosol

2011 ◽  
Vol 11 (3) ◽  
pp. 6999-7044 ◽  
Author(s):  
D. V. Spracklen ◽  
K. S. Carslaw ◽  
U. Pöschl ◽  
A. Rap ◽  
P. M. Forster
Keyword(s):  
Black Carbon ◽  
Carbon Emissions ◽  
Indirect Effect ◽  
Cloud Condensation Nuclei ◽  
Pollution Sources ◽  
Condensation Nuclei ◽  
Aerosol Indirect Effect ◽  
Aerosol Model ◽  
Cloud Albedo ◽  
Global Mean

Abstract. Black carbon in carbonaceous combustion aerosol warms the climate by absorbing solar radiation, meaning reductions in black carbon emissions are often perceived as an attractive global warming mitigation option. However, carbonaceous combustion aerosol can also act as cloud condensation nuclei (particles upon which cloud drops form) so they also cool the climate by increasing cloud albedo. The net radiative effect of carbonaceous combustion aerosol is uncertain because their contribution to cloud drops has not been evaluated on the global scale. By combining extensive observations of cloud condensation nuclei concentrations and a global aerosol model, we show that carbonaceous combustion aerosol accounts for more than half of global cloud condensation nuclei. The evaluated model predicts that wildfire and pollution (fossil fuel and biofuel) carbonaceous combustion aerosol causes a global mean aerosol indirect effect of −0.34 W m−2 due to changes in cloud albedo, with pollution sources alone causing a global mean aerosol indirect effect of −0.23 W m−2. The small size of carbonaceous combustion particles from pollution sources means that whilst they account for only one-third of the emitted mass from these sources they cause two-thirds of the cloud albedo indirect effect that is due to carbonaceous combustion aerosol. This cooling effect must be accounted for to ensure that black carbon emissions controls that reduce the high number concentrations of small pollution particles have the desired net effect on climate.

scholarly journals Global cloud condensation nuclei influenced by carbonaceous combustion aerosol

2011 ◽  
Vol 11 (17) ◽  
pp. 9067-9087 ◽  
Author(s):  
D. V. Spracklen ◽  
K. S. Carslaw ◽  
U. Pöschl ◽  
A. Rap ◽  
P. M. Forster
Keyword(s):  
Black Carbon ◽  
Carbon Emissions ◽  
Indirect Effect ◽  
Fossil Fuel ◽  
Cloud Condensation Nuclei ◽  
Pollution Sources ◽  
Aerosol Indirect Effect ◽  
Cloud Albedo ◽  
Combustion Particles ◽  
Global Mean

Abstract. Black carbon in carbonaceous combustion aerosol warms the climate by absorbing solar radiation, meaning reductions in black carbon emissions are often perceived as an attractive global warming mitigation option. However, carbonaceous combustion aerosol can also act as cloud condensation nuclei (CCN) so they also cool the climate by increasing cloud albedo. The net radiative effect of carbonaceous combustion aerosol is uncertain because their contribution to CCN has not been evaluated on the global scale. By combining extensive observations of CCN concentrations with the GLOMAP global aerosol model, we find that the model is biased low (normalised mean bias = −77 %) unless carbonaceous combustion aerosol act as CCN. We show that carbonaceous combustion aerosol accounts for more than half (52–64 %) of global CCN with the range due to uncertainty in the emitted size distribution of carbonaceous combustion particles. The model predicts that wildfire and pollution (fossil fuel and biofuel) carbonaceous combustion aerosol causes a global mean cloud albedo aerosol indirect effect of −0.34 W m−2, with stronger cooling if we assume smaller particle emission size. We calculate that carbonaceous combustion aerosol from pollution sources cause a global mean aerosol indirect effect of −0.23 W m−2. The small size of carbonaceous combustion particles from fossil fuel sources means that whilst pollution sources account for only one-third of the emitted mass they cause two-thirds of the cloud albedo aerosol indirect effect that is due to carbonaceous combustion aerosol. This cooling effect must be accounted for, along with other cloud effects not studied here, to ensure that black carbon emissions controls that reduce the high number concentrations of fossil fuel particles have the desired net effect on climate.

scholarly journals The aerosol radiative effects of uncontrolled combustion of domestic waste

2016 ◽  
Vol 16 (11) ◽  
pp. 6771-6784 ◽  
Author(s):  
John K. Kodros ◽  
Rachel Cucinotta ◽  
David A. Ridley ◽  
Christine Wiedinmyer ◽  
Jeffrey R. Pierce
Keyword(s):  
Indirect Effect ◽  
Transport Model ◽  
Radiative Effect ◽  
Chemical Transport Model ◽  
Domestic Waste ◽  
Emissions Inventory ◽  
Aerosol Indirect Effect ◽  
Waste Combustion ◽  
Cloud Albedo ◽  
Aerosol Radiative

Abstract. Open, uncontrolled combustion of domestic waste is a potentially significant source of aerosol; however, this aerosol source is not generally included in many global emissions inventories. To provide a first estimate of the aerosol radiative impacts from domestic-waste combustion, we incorporate the Wiedinmyer et al. (2014) emissions inventory into GEOS-Chem-TOMAS, a global chemical-transport model with online aerosol microphysics. We find domestic-waste combustion increases global-mean black carbon and organic aerosol concentrations by 8 and 6 %, respectively, and by greater than 40 % in some regions. Due to uncertainties regarding aerosol optical properties, we estimate the globally averaged aerosol direct radiative effect to range from −5 to −20 mW m−2; however, this range increases from −40 to +4 mW m−2 when we consider uncertainties in emission mass and size distribution. In some regions with significant waste combustion, such as India and China, the aerosol direct radiative effect may exceed −0.4 W m−2. Similarly, we estimate a cloud-albedo aerosol indirect effect of −13 mW m−2, with a range of −4 to −49 mW m−2 due to emission uncertainties. In the regions with significant waste combustion, the cloud-albedo aerosol indirect effect may exceed −0.4 W m−2.

scholarly journals The aerosol radiative effects of uncontrolled combustion of domestic waste

2016 ◽  
Author(s):  
John K. Kodros ◽  
Rachel Cucinotta ◽  
David A. Ridley ◽  
Christine Wiedinmyer ◽  
Jeffrey R. Pierce
Keyword(s):  
Indirect Effect ◽  
Transport Model ◽  
Radiative Effect ◽  
Chemical Transport Model ◽  
Domestic Waste ◽  
Emissions Inventory ◽  
Aerosol Indirect Effect ◽  
Waste Combustion ◽  
Cloud Albedo ◽  
Aerosol Radiative

Abstract. Open, uncontrolled combustion of domestic waste is a potentially significant source of aerosol; however, this aerosol source is not generally included in many global emissions inventories. To provide a first estimate of the aerosol radiative impacts from domestic-waste combustion, we incorporate the Wiedinmyer et al. (2014) emissions inventory into GEOS-Chem-TOMAS, a global chemical-transport model with online aerosol microphysics. We find domestic-waste combustion increases global-mean black carbon and organic aerosol concentrations by 8 % and 6 %, respectively, and by greater than 40 % in some regions. Due to uncertainties regarding aerosol optical properties, we estimate the globally averaged aerosol direct radiative effect to range from −5 mW m−2 to −20 mW m−2; however, this range increases to −40 mW m−2 to &amp;plus;4 mW m−2 when we consider uncertainties in emission mass and size distribution. In some regions with significant waste combustion, such as India and China, the aerosol direct radiative effect may exceed −0.4 W m−2. Similarly, we estimate a cloud-albedo aerosol indirect effect of −13 mW m−2, with a range of −4 mW m−2 to −49 mW m−2 due to emission uncertainties. In the regions with significant waste combustion, the cloud-albedo aerosol indirect effect may exceed −0.4 W m−2.

scholarly journals Summertime observations of ultrafine particles and cloud condensation nuclei from the boundary layer to the free troposphere in the Arctic

2016 ◽  
Author(s):  
Julia Burkart ◽  
Megan D. Willis ◽  
Heiko Bozem ◽  
Jennie L. Thomas ◽  
Kathy Law ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ultrafine Particles ◽  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
Open Ocean ◽  
The Arctic ◽  
Condensation Nuclei ◽  
Aerosol Composition ◽  
Low Level ◽  
20 Nm

Abstract. The Arctic is extremely sensitive to climate change. Shrinking sea ice extent increases the area covered by open ocean during Arctic summer, which impacts the surface albedo and aerosol and cloud properties among many things. In this context extensive aerosol measurements (aerosol composition, particle number and size, cloud condensation nuclei, and trace gases) were made during 11 flights of the NETCARE July, 2014 airborne campaign conducted from Resolute Bay, Nunavut (74N, 94W). Flights routinely included vertical profiles from about 60 to 3000 m a.g.l. as well as several low-level horizontal transects over open ocean, fast ice, melt ponds, and polynyas. Here we discuss the vertical distribution of ultrafine particles (UFP, particle diameter, dp: 5–20 nm), size distributions of larger particles (dp: 20 nm to 1 μm), and cloud condensation nuclei (CCN, supersaturation = 0.6 %) in relation to meteorological conditions and underlying surfaces. UFPs were observed predominantly within the boundary layer, where concentrations were often several hundreds to a few thousand particles per cubic centimeter. Occasionally, particle concentrations below 10 cm−3 were found. The highest UFP concentrations were observed above open ocean and at the top of low-level clouds, whereas numbers over ice-covered regions were substantially lower. Overall, UFP formation events were frequent in a clean boundary layer with a low condensation sink. In a few cases this ultrafine mode extended to sizes larger than 40 nm, suggesting that these UFP can grow into a size range where they can impact clouds and therefore climate.

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