The effect of the photomineralization mechanism on ambient organic aerosols' cloud condensation nuclei and ice nucleation abilities

2020 ◽  
Author(s):  
Silvan Müller ◽  
Nadine Borduas-Dedekind
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Cloud Condensation Nuclei ◽  
Global Climate Model ◽  
Complex Mixture ◽  
Substantial Effect ◽  
Ice Nucleation ◽  
Anthropogenic Sources ◽  
Wood Smoke ◽  
Condensation Nuclei

<p>Organic aerosol (OA) is an important component of the atmospheric submicron particulate mass, consisting of a complex mixture of organic compounds from natural and anthropogenic sources. During its lifetime of approximately one week in the atmosphere, OA is exposed to sunlight and thus undergoes atmospheric processing through photochemistry. This photochemical aging mechanism is thought to have a substantial effect on the propensity of OA to participate in cloud-forming processes by increasing its cloud condensation nuclei (CCN) activity. However, this effect is not well-constrained, and the influence of photochemistry on the ice nucleation (IN) activity of OA is uncertain. In this study, we aim to better understand how the photomineralization mechanism changes the cloud-forming properties of OA by measuring the CCN and IN abilities of photochemically aged OA of different sources: (1) Laboratory-generated ammonium sulfate-methylglyoxal (a proxy for secondary OA), and ambient OA bulk solutions collected from (2) wood smoke and (3) urban particulate matter in Padua (Italy). The solutions are exposed to UV-B radiation in a photoreactor for up to 25 hour and subsequently analyzed for their IN ability and, following aerosolization, for their CCN ability. To correlate changes in cloud-forming properties with changes in chemical composition due to photomineralization, we measure total organic carbon, UV-Vis absorbance, and CO, CO<sub>2</sub>, acetic acid, formic acid, pyruvic acid and oxalic acid production. Indeed, preliminary data of wood smoke OA highlights photomineralization as an important atmospheric aging process that modifies the CCN ability of OA. By characterizing both the CCN and IN abilities of photochemically aged OA, our study may thus provide important insights into the atmospheric evolution and cloud-forming properties of OA, potentially establishing photomineralization of OA as an important mechanism to consider in regional and global climate model predictions.</p>

A closer look at the invisible: Unprecedented levels of ultrafine particles and the hydrological cycle

2021 ◽  
Author(s):  
Wolfgang Junkermann ◽  
Jorg Hacker
Keyword(s):  
Ultrafine Particles ◽  
Climate Model ◽  
Hydrological Cycle ◽  
Global Climate ◽  
Cloud Condensation Nuclei ◽  
Global Climate Model ◽  
Anthropogenic Sources ◽  
Emission Rates ◽  
Weather Patterns ◽  
Sulphur Emissions

<p>Continental as well as maritime ultrafine particles as cloud condensation nuclei (CCN) are likely initially produced by gas to particle conversion starting with nucleation mode aerosol and slowly (within several hours)  growing into CCN sizes. Although these birth and growing processes were well investigated since about 50 years, the source locations, where the anthropogenic fraction of these particles are preferably formed still remain uncertain as well as the strength of individual natural or anthropogenic sources.</p> <p>We present an analysis based on two decades of airborne studies of number and size distribution measurements across Europe, Australia, Mexico and China on nucleation and Aitken mode particles serving as CCN or their precursors. Selected flight patterns allow source apportionment for typical major sources and even a quantitative estimate of their emission rates. </p> <p>Contrary to current global climate model RCP assumptions with decreasing aerosol from 2005 towards the end of the century trends of ultrafine particles and CCN are no longer correlated to sulphur emissions within the last two decades. Nowadays nitrogen and ammonia chemistry is becoming increasingly important for global anthropogenic nanoparticle particle formation and number concentrations. Due to their impact on the hydrological cycle, changes like a slowdown of raindrop production, an increased latent heat flux into the lower free troposphere, an invigoration of torrential rains and a larger water vapour column density might be the consequences. Such recently observed weather patterns are well in agreement with current observations of regional UFP/CCN concentrations and their timely evolution.</p>

scholarly journals Aerosol specification in single-column CAM5

2014 ◽  
Vol 7 (6) ◽  
pp. 7693-7731
Author(s):  
B. Lebassi-Habtezion ◽  
P. Caldwell
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Strong Dependence ◽  
Ice Nucleation ◽  
Ice Crystal ◽  
Shallow Convection ◽  
Single Column ◽  
The Impact

Abstract. The ability to run a global climate model in single-column mode is very useful for testing model improvements because single-column models (SCMs) are inexpensive to run and easy to interpret. A major breakthrough in Version 5 of the Community Atmosphere Model (CAM5) is the inclusion of prognostic aerosol. Unfortunately, this improvement was not coordinated with the SCM version of CAM5 and as a result CAM5-SCM initializes aerosols to zero. In this study we explore the impact of running CAM5-SCM with aerosol initialized to zero (hereafter named Default) and test three potential fixes. The first fix is to use CAM5's prescribed aerosol capability, which specifies aerosols at monthly climatological values. The second method is to prescribe aerosols at observed values. The third approach is to fix droplet and ice crystal numbers at prescribed values. We test our fixes in four different cloud regimes to ensure representativeness: subtropical drizzling stratocumulus (based on the DYCOMS RF02 case study), mixed-phase Arctic stratocumulus (using the MPACE-B case study), tropical shallow convection (using the RICO case study), and summertime mid-latitude continental convection (using the ARM95 case study). Stratiform cloud cases (DYCOMS RF02 and MPACE-B) were found to have a strong dependence on aerosol concentration, while convective cases (RICO and ARM95) were relatively insensitive to aerosol specification. This is perhaps expected because convective schemes in CAM5 do not currently use aerosol information. Adequate liquid water content in the MPACE-B case was only maintained when ice crystal number concentration was specified because the Meyers et al. (1992) deposition/condensation ice nucleation scheme used by CAM5 greatly overpredicts ice nucleation rates, causing clouds to rapidly glaciate. Surprisingly, predicted droplet concentrations for the ARM95 region in both SCM and global runs were around 25 cm−3, which is much lower than observed. This finding suggests that CAM5 has problems capturing aerosol effects in this climate regime.

scholarly journals Contribution of primary carbonaceous aerosol to cloud condensation nuclei: processes and uncertainties evaluated with a global aerosol microphysics model

2007 ◽  
Vol 7 (20) ◽  
pp. 5447-5466 ◽  
Author(s):  
J. R. Pierce ◽  
K. Chen ◽  
P. J. Adams
Keyword(s):  
Size Distribution ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Global Climate Model ◽  
Organic Aerosol ◽  
Carbonaceous Aerosol ◽  
Condensation Nuclei ◽  
Carbonaceous Particles ◽  
Seeding Effect ◽  
Inorganic Aerosol

Abstract. This paper explores the impacts of primary carbonaceous aerosol on cloud condensation nuclei (CCN) concentrations in a global climate model with size-resolved aerosol microphysics. Organic matter (OM) and elemental carbon (EC) from two emissions inventories were incorporated into a preexisting model with sulfate and sea-salt aerosol. The addition of primary carbonaceous aerosol increased CCN(0.2%) concentrations by 65–90% in the globally averaged surface layer depending on the carbonaceous emissions inventory used. Sensitivity studies were performed to determine the relative importance of organic solubility/hygroscopicity in predicting CCN. In a sensitivity study where carbonaceous aerosol was assumed to be completely insoluble, concentrations of CCN(0.2%) still increased by 40–50% globally over the no carbonaceous simulation because primary carbonaceous emissions were able to become CCN via condensation of sulfuric acid. This shows that approximately half of the contribution of primary carbonaceous particles to CCN in our model comes from the addition of new particles (seeding effect) and half from the contribution of organic solute (solute effect). The solute effect tends to dominate more in areas where there is less inorganic aerosol than organic aerosol and the seeding effect tends to dominate in areas where there is more inorganic aerosol than organic aerosol. It was found that an accurate simulation of the number size distribution is necessary to predict the CCN concentration but assuming an average chemical composition will generally give a CCN concentration within a factor of 2. If a "typical" size distribution is assumed for each species when calculating CCN, such as is done in bulk aerosol models, the mean error relative to a simulation with size resolved microphysics is on the order of 35%. Predicted values of carbonaceous aerosol mass and aerosol number were compared to observations and the model showed average errors of a factor of 3 for carbonaceous mass and a factor of 4 for total aerosol number; however, errors in the accumulation mode concentrations were found to be lower in comparisons with European and marine observations.. The errors in CN and carbonaceous mass may be reduced by improving the emission size distributions of both primary sulfate and primary carbonaceous aerosol.

scholarly journals Bacteria in the ECHAM5-HAM global climate model

2012 ◽  
Vol 12 (18) ◽  
pp. 8645-8661 ◽  
Author(s):  
A. Sesartic ◽  
U. Lohmann ◽  
T. Storelvmo
Keyword(s):  
Active Sites ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Liquid Water Path ◽  
Water Path ◽  
Ice Nuclei ◽  
Ice Water

Abstract. Some bacteria are among the most active ice nuclei found in nature due to the ice nucleation active proteins on their surface, which serve as active sites for ice nucleation. Their potential impact on clouds and precipitation is not well known and needs to be investigated. Bacteria as a new aerosol species were introduced into the global climate model (GCM) ECHAM5-HAM. The inclusion of bacteria acting as ice nuclei in a GCM leads to only minor changes in cloud formation and precipitation on a global level, however, changes in the liquid water path and ice water path are simulated, specifically in the boreal regions where tundra and forests act as sources of bacteria. Although bacteria contribute to heterogeneous freezing, their impact is reduced by their low numbers compared to other heterogeneous IN. This result confirms the outcome of several previous studies.

scholarly journals Contribution of carbonaceous aerosol to cloud condensation nuclei: processes and uncertainties evaluated with a global aerosol microphysics model

2007 ◽  
Vol 7 (3) ◽  
pp. 7723-7765 ◽  
Author(s):  
J. R. Pierce ◽  
K. Chen ◽  
P. J. Adams
Keyword(s):  
Size Distribution ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Global Climate Model ◽  
Organic Aerosol ◽  
Carbonaceous Aerosol ◽  
Condensation Nuclei ◽  
Carbonaceous Particles ◽  
Seeding Effect ◽  
Inorganic Aerosol

Abstract. This paper explores the impacts of carbonaceous aerosol on cloud condensation nuclei (CCN) concentrations in a global climate model with size-resolved aerosol microphysics. Organic matter (OM) and elemental carbon (EC) from two emissions inventories were incorporated into a preexisting model with sulfate and sea-salt aerosol. The addition of carbonaceous aerosol increased CCN(0.2%) concentrations by 65–90% in the globally averaged surface layer depending on the carbonaceous emissions inventory used. Sensitivity studies were performed to determine the relative importance of the organic "solute effect", in which CCN concentrations increase because of the added soluble carbonaceous material, versus the "seeding effect", in which CCN concentrations increase because of increased particle number concentrations. In a sensitivity study where carbonaceous aerosol was assumed to be completely insoluble, concentrations of CCN(0.2%) still increased by 40–50% globally over the no carbonaceous simulation because primary carbonaceous emissions were able to become CCN via condensation of sulfuric acid. This shows that approximately half of the contribution of carbonaceous particles to CCN comes from the "seeding effect" and half from the "solute effect". The solute effect tends to dominate more in areas where there is less inorganic aerosol than organic aerosol and the seeding effect tends to dominate in areas where is more inorganic aerosol than organic aerosol. It was found that an accurate simulation of the number size distribution is necessary to predict the CCN concentration but assuming an average chemical composition will generally give a CCN concentration within a factor of 2. If a "typical" size distribution is assumed for each species when calculating CCN, such as is done in bulk aerosol models, the mean error relative to a simulation with size resolved microphysics is on the order of 35%. Predicted values of carbonaceous aerosol mass and aerosol number were compared to observations and the model showed average errors of a factor of 3 for carbonaceous mass and a factor of 4 for total aerosol number. These errors may be reduced by improving the emission size distributions of both primary sulfate and primary carbonaceous aerosol.

scholarly journals The value of remote marine aerosol measurements for constraining radiative forcing uncertainty

2020 ◽  
Vol 20 (16) ◽  
pp. 10063-10072 ◽  
Author(s):  
Leighton A. Regayre ◽  
Julia Schmale ◽  
Jill S. Johnson ◽  
Christian Tatzelt ◽  
Andrea Baccarini ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Northern Hemisphere ◽  
Radiative Forcing ◽  
Climate Model ◽  
Global Climate ◽  
Cloud Condensation Nuclei ◽  
Global Climate Model ◽  
Model Parameters ◽  
Marine Aerosol ◽  
Aerosol Emissions

Abstract. Aerosol measurements over the Southern Ocean are used to constrain aerosol–cloud interaction radiative forcing (RFaci) uncertainty in a global climate model. Forcing uncertainty is quantified using 1 million climate model variants that sample the uncertainty in nearly 30 model parameters. Measurements of cloud condensation nuclei and other aerosol properties from an Antarctic circumnavigation expedition strongly constrain natural aerosol emissions: default sea spray emissions need to be increased by around a factor of 3 to be consistent with measurements. Forcing uncertainty is reduced by around 7 % using this set of several hundred measurements, which is comparable to the 8 % reduction achieved using a diverse and extensive set of over 9000 predominantly Northern Hemisphere measurements. When Southern Ocean and Northern Hemisphere measurements are combined, uncertainty in RFaci is reduced by 21 %, and the strongest 20 % of forcing values are ruled out as implausible. In this combined constraint, observationally plausible RFaci is around 0.17 W m−2 weaker (less negative) with 95 % credible values ranging from −2.51 to −1.17 W m−2 (standard deviation of −2.18 to −1.46 W m−2). The Southern Ocean and Northern Hemisphere measurement datasets are complementary because they constrain different processes. These results highlight the value of remote marine aerosol measurements.

scholarly journals A Classical-Theory-Based Parameterization of Heterogeneous Ice Nucleation by Mineral Dust, Soot, and Biological Particles in a Global Climate Model

2010 ◽  
Vol 67 (8) ◽  
pp. 2483-2503 ◽  
Author(s):  
Corinna Hoose ◽  
Jón Egill Kristjánsson ◽  
Jen-Ping Chen ◽  
Anupam Hazra
Keyword(s):  
Climate Model ◽  
Mineral Dust ◽  
Global Climate ◽  
Global Climate Model ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Ice Formation ◽  
Biological Particles ◽  
Ice Nuclei ◽  
Immersion Freezing

Abstract An ice nucleation parameterization based on classical nucleation theory, with aerosol-specific parameters derived from experiments, has been implemented into a global climate model—the Community Atmosphere Model (CAM)-Oslo. The parameterization treats immersion, contact, and deposition nucleation by mineral dust, soot, bacteria, fungal spores, and pollen in mixed-phase clouds at temperatures between 0° and −38°C. Immersion freezing is considered for insoluble particles that are activated to cloud droplets, and deposition and contact nucleation are only allowed for uncoated, unactivated aerosols. Immersion freezing by mineral dust is found to be the dominant ice formation process, followed by immersion and contact freezing by soot. The simulated biological aerosol contribution to global atmospheric ice formation is marginal, even with high estimates of their ice nucleation activity, because the number concentration of ice nucleation active biological particles in the atmosphere is low compared to other ice nucleating aerosols. Because of the dominance of mineral dust, the simulated ice nuclei concentrations at temperatures below −20°C are found to correlate with coarse-mode aerosol particle concentrations. The ice nuclei (IN) concentrations in the model agree well overall with in situ continuous flow diffusion chamber measurements. At individual locations, the model exhibits a stronger temperature dependence on IN concentrations than what is observed. The simulated IN composition (77% mineral dust, 23% soot, and 10−5% biological particles) lies in the range of observed ice nuclei and ice crystal residue compositions.

scholarly journals Bacteria in the ECHAM5-HAM global climate model

2011 ◽  
Vol 11 (1) ◽  
pp. 1457-1488 ◽  
Author(s):  
A. Sesartic ◽  
U. Lohmann ◽  
T. Storelvmo
Keyword(s):  
Active Sites ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Liquid Water Path ◽  
Water Path ◽  
Ice Nuclei ◽  
Ice Water

Abstract. Bacteria are the most active naturally occuring ice nuclei (IN) due to the ice nucleation active proteins on their surface, which serve as active sites for ice nucleation. Their potential impact on clouds and precipitation is not well known and needs to be investigated. Bacteria as a new aerosol species were introduced into the global climate model (GCM) ECHAM5-HAM. The inclusion of bacteria acting as IN in a GCM leads to only minor changes in cloud formation and precipitation on a global level, however, changes in the liquid water path and ice water path can be observed, specifically in the boreal regions where tundra and forests act as sources of bacteria.

scholarly journals Brightening of the global cloud field by nitric acid and the associated radiative forcing

2012 ◽  
Vol 12 (2) ◽  
pp. 5225-5245
Author(s):  
R. Makkonen ◽  
S. Romakkaniemi ◽  
H. Kokkola ◽  
P. Stier ◽  
P. Räisänen ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Indirect Effect ◽  
Radiative Forcing ◽  
Climate Model ◽  
Global Climate ◽  
Cloud Condensation Nuclei ◽  
Global Climate Model ◽  
So2 Emissions ◽  
Cloud Albedo ◽  
Albedo Effect

Abstract. Clouds cool Earth's climate by reflecting 20 % of the incoming solar energy, while also trapping part of the outgoing radiation. The effect of human activities on clouds is poorly understood, but the present-day anthropogenic cooling via changes of cloud albedo and lifetime could be of the same order as warming from anthropogenic addition in CO2. Soluble trace gases can increase water condensation to particles, possibly leading to activation of smaller aerosols and more numerous cloud droplets. We have studied the effect of nitric acid on the aerosol indirect effect with a global climate model. The nitric acid contribution to the present-day cloud albedo effect was found to be −0.32 W m−2 and the total indirect effect −0.46 W m−2. The contribution to the cloud albedo effect is shown to increase to −0.37 W m−2 by 2100, if considering only the reductions in available cloud condensation nuclei. Overall, the effect of nitric acid can play a large part in aerosol cooling during the following decades with decreasing SO2 emissions and increasing NOx and greenhouse gases.

High bit rate ACTS experiments for performing global science - Keck Telescope and global climate model

1996 ◽  
Author(s):  
Larry Bergman ◽  
J. Gary ◽  
Burt Edelson ◽  
Neil Helm ◽  
Judith Cohen ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Bit Rate ◽  
Global Science ◽  
High Bit Rate
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