| 1. |
- Boy, Michael, et al.
(författare)
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Positive feedback mechanism between biogenic volatile organic compounds and the methane lifetime in future climates
- 2022
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Ingår i: npj Climate and Atmospheric Science. - : Springer Science and Business Media LLC. - 2397-3722. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- A multitude of biogeochemical feedback mechanisms govern the climate sensitivity of Earth in response to radiation balance perturbations. One feedback mechanism, which remained missing from most current Earth System Models applied to predict future climate change in IPCC AR6, is the impact of higher temperatures on the emissions of biogenic volatile organic compounds (BVOCs), and their subsequent effects on the hydroxyl radical (OH) concentrations. OH, in turn, is the main sink term for many gaseous compounds including methane, which is the second most important human-influenced greenhouse gas in terms of climate forcing. In this study, we investigate the impact of this feedback mechanism by applying two models, a one-dimensional chemistry-transport model, and a global chemistry-transport model. The results indicate that in a 6 K temperature increase scenario, the BVOC-OH-CH4 feedback increases the lifetime of methane by 11.4% locally over the boreal region when the temperature rise only affects chemical reaction rates, and not both, chemistry and BVOC emissions. This would lead to a local increase in radiative forcing through methane (ΔRFCH4) of approximately 0.013 Wm−2 per year, which is 2.1% of the current ΔRFCH4. In the whole Northern hemisphere, we predict an increase in the concentration of methane by 0.024% per year comparing simulations with temperature increase only in the chemistry or temperature increase in chemistry and BVOC emissions. This equals approximately 7% of the annual growth rate of methane during the years 2008–2017 (6.6 ± 0.3 ppb yr−1) and leads to an ΔRFCH4 of 1.9 mWm−2 per year.
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| 2. |
- Chen, Dean, et al.
(författare)
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A modelling study of OH, NO3 and H2SO4 in 2007- 2018 at SMEAR II, Finland : Analysis of long-term trends
- 2021
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Ingår i: Environmental Science: Atmospheres. - : Royal Society of Chemistry (RSC). - 2634-3606. ; 1:6, s. 449-472
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Tidskriftsartikel (refereegranskat)abstract
- Major atmospheric oxidants (OH,O3 and NO3) dominate the atmospheric oxidation capacity, while H2SO4 is considered as a main driver for new particle formation. Although numerous studies have investigated the long-term trend of ozone in Europe, the trends of OH, NO3 and H2SO4 at specific sites are to a large extent unknown. The one-dimensional model SOSAA has been applied in several studies at the SMEAR II station and has been validated by measurements in several projects. Here, we applied the SOSAA model for the years 2007-2018 to simulate the atmospheric chemical components, especially the atmospheric oxidants OH and NO3, as well as H2SO4 at SMEAR II. The simulations were evaluated with observations from several shorter and longer campaigns at SMEAR II. Our results show that daily OH increased by 2.39% per year and NO3 decreased by 3.41% per year, with different trends of these oxidants during day and night. On the contrary, daytime sulfuric acid concentrations decreased by 2.78% per year, which correlated with the observed decreasing concentration of newly formed particles in the size range of 3- 25 nm with 1.4% per year at SMEAR II during the years 1997-2012. Additionally, we compared our simulated OH, NO3 and H2SO4 concentrations with proxies, which are commonly applied in case a limited number of parameters are measured and no detailed model simulations are available.
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| 3. |
- Clusius, Petri, et al.
(författare)
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Atmospherically Relevant Chemistry and Aerosol box model - ARCA box (version 1.2)
- 2022
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 15:18, s. 7257-7286
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Tidskriftsartikel (refereegranskat)abstract
- We introduce the Atmospherically Relevant Chemistry and Aerosol box model ARCA box (v.1.2.2). It is a zero-dimensional process model with a focus on atmospheric chemistry and submicron aerosol processes, including cluster formation. A novel feature in the model is its comprehensive graphical user interface, allowing for detailed configuration and documentation of the simulation settings, flexible model input, and output visualization. Additionally, the graphical interface contains tools for module customization and input data acquisition. These properties - customizability, ease of implementation and repeatability - make ARCA an invaluable tool for any atmospheric scientist who needs a view on the complex atmospheric aerosol processes. ARCA is based on previous models (MALTE-BOX, ADiC and ADCHEM), but the code has been fully rewritten and reviewed. The gas-phase chemistry module incorporates the Master Chemical Mechanism (MCMv3.3.1) and Peroxy Radical Autoxidation Mechanism (PRAM) but can use any compatible chemistry scheme. ARCA's aerosol module couples the ACDC (Atmospheric Cluster Dynamics Code) in its particle formation module, and the discrete particle size representation includes the fully stationary and fixed-grid moving average methods. ARCA calculates the gas-particle partitioning of low-volatility organic vapours for any number of compounds included in the chemistry, as well as the Brownian coagulation of the particles. The model has parametrizations for vapour and particle wall losses but accepts user-supplied time- and size-resolved input. ARCA is written in Fortran and Python (user interface and supplementary tools), can be installed on any of the three major operating systems and is licensed under GPLv3.
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| 4. |
- Foreback, Benjamin, et al.
(författare)
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A new implementation of FLEXPART with Enviro-HIRLAM meteorological input, and a case study during a heavy air pollution event
- 2024
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Ingår i: big earth data. - 2096-4471.
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Tidskriftsartikel (refereegranskat)abstract
- We integrated Enviro-HIRLAM (Environment-High Resolution Limited Area Model) meteorological output into FLEXPART (FLEXible PARTicle dispersion model). A FLEXPART simulation requires meteorological input from a numerical weather prediction (NWP) model. The publicly available version of FLEXPART can utilize either ECMWF (European Centre for Medium-range Weather Forecasts) Integrated Forecast System (IFS) forecast or reanalysis NWP data, or NCEP (U.S. National Center for Environmental Prediction) Global Forecast System (GFS) forecast or reanalysis NWP data. The primary benefits of using Enviro-HIRLAM are that it runs at a higher resolution and accounts for aerosol effects in meteorological fields. We compared backward trajectories generated with FLEXPART using Enviro-HIRLAM (both with and without aerosol effects) to trajectories generated using NCEP GFS and ECMWF IFS meteorological inputs, for a case study of a heavy haze event which occurred in Beijing, China in November 2018. We found that results from FLEXPART were considerably different when using different meteorological inputs. When aerosol effects were included in the NWP, there was a small but noticeable difference in calculated trajectories. Moreover, when looking at potential emission sensitivity instead of simply expressing trajectories as lines, additional information, which may have been missed when looking only at trajectories as lines, can be inferred.
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| 5. |
- Qi, Ximeng, et al.
(författare)
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Modelling studies of HOMs and their contributions to new particle formation and growth : Comparison of boreal forest in Finland and a polluted environment in China
- 2018
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:16, s. 11779-11791
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Tidskriftsartikel (refereegranskat)abstract
- Highly oxygenated multifunctional compounds (HOMs) play a key role in new particle formation (NPF), but their quantitative roles in different environments of the globe have not been well studied yet. Frequent NPF events were observed at two flagship stations under different environmental conditions, i.e. a remote boreal forest site (SMEAR II) in Finland and a suburban site (SORPES) in polluted eastern China. The averaged formation rate of 6 nm particles and the growth rate of 6-30 nm particles were 0.3 cm-3 s-1 and 4.5 nm h-1 at SMEAR II compared to 2.3 cm-3 s-1 and 8.7 nm h-1 at SORPES, respectively. To explore the differences of NPF at the two stations, the HOM concentrations and NPF events at two sites were simulated with the MALTE-BOX model, and their roles in NPF and particle growth in the two distinctly different environments are discussed. The model provides an acceptable agreement between the simulated and measured concentrations of sulfuric acid and HOMs at SMEAR II. The sulfuric acid and HOM organonitrate concentrations are significantly higher but other HOM monomers and dimers from monoterpene oxidation are lower at SORPES compared to SMEAR II. The model simulates the NPF events at SMEAR II with a good agreement but underestimates the growth of new particles at SORPES, indicating a dominant role of anthropogenic processes in the polluted environment. HOMs from monoterpene oxidation dominate the growth of ultrafine particles at SMEAR II while sulfuric acid and HOMs from aromatics oxidation play a more important role in particle growth. This study highlights the distinct roles of sulfuric acid and HOMs in NPF and particle growth in different environmental conditions and suggests the need for molecular-scale measurements in improving the understanding of NPF mechanisms in polluted areas like eastern China.
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| 6. |
- Stolzenburg, Dominik, et al.
(författare)
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Atmospheric nanoparticle growth
- 2023
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Ingår i: Reviews of Modern Physics. - 0034-6861 .- 1539-0756. ; 95:4
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Forskningsöversikt (refereegranskat)abstract
- New particle formation of liquid or solid nanoparticles from gas-phase precursors is a decisive process in Earth’s atmosphere and is considered one of the largest uncertainties in climate change predictions. Key for the climate relevance of new particle formation is the growth of freshly formed molecular clusters, as it determines the survival of these particles to cloud condensation nuclei sizes, where they can contribute to the aerosol-indirect effect. This review lays out the fundamental definitions of nanoparticle growth and addresses the rapidly emerging field of new particle formation studies with a focus on the diverse processes contributing to nanoparticle growth, explicitly comparing the latest experimental findings and their implementation in large-scale models. Atmospheric nanoparticle growth is a complex phenomenon including condensational and reactive vapor uptake, aerosol coagulation, and sink processes. It is linked to thermodynamics, cluster- and phase-transition physics. Nanoparticle growth rates measured from the evolution of the particle-size distribution describe growth as a collective phenomenon, while models often interpret them on a single-particle level and incorporate it into highly simplified size-distribution representations. Recent atmospheric observations show that sulfuric acid together with ammonia and amines, iodic acid, and oxidized organic species can contribute to nanoparticle growth, whereas most models describe the growth effects from a limited subset of this variety of condensable vapors. Atmospheric simulation chamber experiments have clarified the role of ions, intermolecular forces, the interplay of acids and bases, and the contribution of different types of organic vapors. Especially in the complex thermodynamics of organic vapor condensation, the field has had noteworthy advances over the last decade. While the experimental field has achieved significant progress in methodology and process level understanding, this has not led to a similar improvement in the description of the climate impact of nanoparticle formation in large-scale models. This review sets the basis to better align experimental and modeling studies on nanoparticle growth, giving specific guidance for future studies aiming to resolve the questions as to why the climate response in large-scale models seems to be buffered against high survival probabilities and why the global growth observations herein show surprisingly low variation.
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| 7. |
- Tang, Jing, et al.
(författare)
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High-latitude vegetation changes will determine future plant volatile impacts on atmospheric organic aerosols
- 2023
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Ingår i: npj Climate and Atmospheric Science. - 2397-3722. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Strong, ongoing high-latitude warming is causing changes to vegetation composition and plant productivity, modifying plant emissions of biogenic volatile organic compounds (BVOCs). In the sparsely populated high latitudes with clean background air, climate feedback resulting from BVOCs as precursors of atmospheric aerosols could be more important than elsewhere on the globe. Here, we quantitatively assess changes in vegetation composition, BVOC emissions, and secondary organic aerosol (SOA) formation under different climate scenarios. We show that warming-induced vegetation changes largely determine the spatial patterns of future BVOC impacts on SOA. The northward advances of boreal needle-leaved woody species result in increased SOA optical depth by up to 41%, causing cooling feedback. However, areas with temperate broad-leaved trees replacing boreal needle-leaved trees likely experience a large decline in monoterpene emissions and SOA formation, causing warming feedback. We highlight the necessity of considering warming-induced vegetation shifts when assessing land radiative feedback on climate following the BVOC-SOA pathway.
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| 8. |
- Xavier, Carlton, et al.
(författare)
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Aerosol mass yields of selected biogenic volatile organic compounds - A theoretical study with nearly explicit gas-phase chemistry
- 2019
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:22, s. 13741-13758
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Tidskriftsartikel (refereegranskat)abstract
- In this study we modeled secondary organic aerosol (SOA) mass loadings from the oxidation (by O3, OH and NO3) of five representative biogenic volatile organic compounds (BVOCs): isoprene, endocyclic bond-containing monoterpenes (α-pinene and limonene), exocyclic double-bond compound (β-pinene) and a sesquiterpene (β-caryophyllene). The simulations were designed to replicate an idealized smog chamber and oxidative flow reactors (OFRs). The Master Chemical Mechanism (MCM) together with the peroxy radical autoxidation mechanism (PRAM) were used to simulate the gas-phase chemistry. The aim of this study was to compare the potency of MCM and MCM + PRAM in predicting SOA formation. SOA yields were in good agreement with experimental values for chamber simulations when MCM + PRAM was applied, while a stand-alone MCM underpredicted the SOA yields. Compared to experimental yields, the OFR simulations using MCM + PRAM yields were in good agreement for BVOCs oxidized by both O3 and OH. On the other hand, a stand-alone MCM underpredicted the SOA mass yields. SOA yields increased with decreasing temperatures and NO concentrations and vice versa. This highlights the limitations posed when using fixed SOA yields in a majority of global and regional models. Few compounds that play a crucial role (>95 % of mass load) in contributing to SOA mass increase (using MCM + PRAM) are identified. The results further emphasized that incorporating PRAM in conjunction with MCM does improve SOA mass yield estimation..
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| 9. |
- Zhou, Putian, et al.
(författare)
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Simulating dust emissions and secondary organic aerosol formation over northern Africa during the mid-Holocene Green Sahara period
- 2023
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Ingår i: Climate of the Past. - 1814-9324 .- 1814-9332. ; 19:12, s. 2445-2462
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Tidskriftsartikel (refereegranskat)abstract
- Paleo-proxy data indicate that a “Green Sahara” thrived in northern Africa during the early- to mid-Holocene (MH; 11 000 to 5000 years before present), characterized by more vegetation cover and reduced dust emissions. Utilizing a state-of-the-art atmospheric chemical transport model, TM5-MP, we assessed the changes in biogenic volatile organic compound (BVOC) emissions, dust emissions and secondary organic aerosol (SOA) concentrations in northern Africa during this period relative to the pre-industrial (PI) period. Our simulations show that dust emissions reduced from 280.6 Tg a−1 in the PI to 26.8 Tg a−1 in the MH, agreeing with indications from eight marine sediment records in the Atlantic Ocean. The northward expansion in northern Africa resulted in an increase in annual emissions of isoprene and monoterpenes during the MH, around 4.3 and 3.5 times higher than that in the PI period, respectively, causing a 1.9-times increase in the SOA surface concentration. Concurrently, enhanced BVOC emissions consumed more hydroxyl radical (OH), resulting in less sulfate formation. This effect counteracted the enhanced SOA surface concentration, altogether leading to a 17 % increase in the cloud condensation nuclei at 0.2 % super saturation over northern Africa. Our simulations provide consistent emission datasets of BVOCs, dust and the SOA formation aligned with the northward shift of vegetation during the “Green Sahara” period, which could serve as a benchmark for MH aerosol input in future Earth system model simulation experiments.
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| 10. |
- Öström, Emilie, et al.
(författare)
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Modeling the role of highly oxidized multifunctional organic molecules for the growth of new particles over the boreal forest region
- 2017
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 17:14, s. 8887-8901
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the processes behind observed new particle formation (NPF) events and subsequent organic-dominated particle growth at the Pallas Atmosphere-Ecosystem Supersite in Northern Finland are explored with the one-dimensional column trajectory model ADCHEM. The modeled sub-micron particle mass is up to ∼75 % composed of SOA formed from highly oxidized multifunctional organic molecules (HOMs) with low or extremely low volatility. In the model the newly formed particles with an initial diameter of 1.5 nm reach a diameter of 7 nm about 2 h earlier than what is typically observed at the station. This is an indication that the model tends to overestimate the initial particle growth. In contrast, the modeled particle growth to CCN size ranges (> 50 nm in diameter) seems to be underestimated because the increase in the concentration of particles above 50 nm in diameter typically occurs several hours later compared to the observations. Due to the high fraction of HOMs in the modeled particles, the oxygen-to-carbon (O : C) atomic ratio of the SOA is nearly 1. This unusually high O : C and the discrepancy between the modeled and observed particle growth might be explained by the fact that the model does not consider any particle-phase reactions involving semi-volatile organic compounds with relatively low O : C. In the model simulations where condensation of low-volatility and extremely low-volatility HOMs explain most of the SOA formation, the phase state of the SOA (assumed either liquid or amorphous solid) has an insignificant impact on the evolution of the particle number size distributions. However, the modeled particle growth rates are sensitive to the method used to estimate the vapor pressures of the HOMs. Future studies should evaluate how heterogeneous reactions involving semi-volatility HOMs and other less-oxidized organic compounds can influence the SOA composition- and size-dependent particle growth.
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