Weaker cooling by aerosols due to dust–pollution interactions

Abstract. The interactions between aeolian dust and anthropogenic air pollution, notably chemical ageing of mineral dust and coagulation of dust and pollution particles, modify the atmospheric aerosol composition and burden. Since the aerosol particles can act as cloud condensation nuclei, this affects the radiative transfer not only directly via aerosol–radiation interactions, but also indirectly through cloud adjustments. We study both radiative effects using the global ECHAM/MESSy atmospheric chemistry-climate model (EMAC) which combines the Modular Earth Submodel System (MESSy) with the European Centre/Hamburg (ECHAM) climate model. Our simulations show that dust–pollution–cloud interactions reduce the condensed water path and hence the reflection of solar radiation. The associated climate warming outweighs the cooling that the dust–pollution interactions exert through the direct radiative effect. In total, this results in a net warming by dust–pollution interactions which moderates the negative global anthropogenic aerosol forcing at the top of the atmosphere by (0.2 ± 0.1) W m−2.

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Weaker cooling by aerosols due to dust-pollution interactions

10.5194/acp-2020-531 ◽

2020 ◽

Cited By ~ 1

Author(s):

Klaus Klingmüller ◽

Vlassis A. Karydis ◽

Sara Bacer ◽

Georgiy L. Stenchikov ◽

Jos Lelieveld

Keyword(s):

Atmospheric Chemistry ◽

Climate Model ◽

Cloud Condensation Nuclei ◽

Cloud Water ◽

Radiative Effect ◽

Dust Pollution ◽

Aerosol Composition ◽

Anthropogenic Aerosol ◽

Aerosol Forcing ◽

Chemical Ageing

Abstract. The interactions between aeolian dust and anthropogenic air pollution, notably chemical ageing of mineral dust and coagulation of dust and pollution particles, modify the atmospheric aerosol composition and burden. Since the aerosol particles can act as cloud condensation nuclei, this not only affects the radiative transfer directly via aerosol-radiation interactions, but also indirectly through cloud adjustments. We study both radiative effects using the global ECHAM/MESSy atmospheric chemistry-climate model (EMAC) which combines the Modular Earth Submodel System (MESSy) with the European Centre/Hamburg (ECHAM) climate model. Our simulations show that dust-pollution interactions reduce the cloud water path and hence the reflection of solar radiation. The associated climate warming outweighs the cooling which the dust-pollution interactions exert through the direct radiative effect. In total, this results in a net warming by dust-pollution interactions which moderates the negative global anthropogenic aerosol forcing at the top of the atmosphere by (0.2 ± 0.1) W m−2.

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Weaker cooling by aerosols due to dust-pollution interactions

10.5194/egusphere-egu2020-8381 ◽

2020 ◽

Author(s):

Klaus Klingmueller ◽

Vlassis Karydis ◽

Sara Bacer ◽

Georgiy Stenchikov ◽

Jos Lelieveld

Keyword(s):

Atmospheric Chemistry ◽

Climate Model ◽

Cloud Condensation Nuclei ◽

Aerosol Particles ◽

Cloud Water ◽

Radiative Effect ◽

Dust Pollution ◽

Anthropogenic Aerosol ◽

Aerosol Forcing ◽

Chemical Ageing

The interactions between aeolian dust and anthropogenic air pollution, notably chemical ageing of mineral dust and coagulation of dust and pollution particles, modify the atmospheric aerosol burden. Since the aerosol particles can act as cloud condensation nuclei, this not only affects the radiative transfer directly via aerosol radiation interactions, but also indirectly through cloud adjustments. We study both radiative effects using the global ECHAM/MESSy atmospheric chemistry-climate model (EMAC) which combines the Modular Earth Submodel System (MESSy) with the European Centre/Hamburg (ECHAM) climate model. Our simulations show that the dust-pollution interactions reduce the cloud water and hence the reflection of solar radiation. The associated climate warming outweighs the cooling which the dust-pollution interactions exert through the direct radiative effect. In total, this results in a net warming by dust-pollution interactions which we estimate to moderate the negative global anthropogenic aerosol forcing at the top of the atmosphere by more than 0.1 W / m&#178;.

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Direct radiative effect of dust–pollution interactions

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-7397-2019 ◽

2019 ◽

Vol 19 (11) ◽

pp. 7397-7408 ◽

Cited By ~ 8

Author(s):

Klaus Klingmüller ◽

Jos Lelieveld ◽

Vlassis A. Karydis ◽

Georgiy L. Stenchikov

Keyword(s):

Air Pollution ◽

Chemical Composition ◽

Atmospheric Chemistry ◽

Radiative Forcing ◽

Climate Model ◽

Climate Forcing ◽

Dust Particles ◽

Radiative Effect ◽

Dust Pollution ◽

Hygroscopic Properties

Abstract. The chemical ageing of aeolian dust, through interactions with air pollution, affects the optical and hygroscopic properties of the mineral particles and hence their atmospheric residence time and climate forcing. Conversely, the chemical composition of the dust particles and their role as coagulation partners impact the abundance of particulate air pollution. This results in a change in the aerosol direct radiative effect that we interpret as an anthropogenic radiative forcing associated with mineral dust–pollution interactions. Using the ECHAM/MESSy atmospheric chemistry climate model (EMAC), which combines the Modular Earth Submodel System (MESSy) with the European Centre Hamburg (ECHAM) climate model, including a detailed parametrisation of ageing processes and an emission scheme accounting for the chemical composition of desert soils, we study the direct radiative forcing globally and regionally, considering solar and terrestrial radiation. Our results indicate positive and negative forcings, depending on the region. The predominantly negative forcing at the top of the atmosphere over large parts of the dust belt, from West Africa to East Asia, attains a maximum of about −2 W m−2 south of the Sahel, in contrast to a positive forcing over India. Globally averaged, these forcings partially counterbalance, resulting in a net negative forcing of −0.05 W m−2, which nevertheless represents a considerable fraction (40 %) of the total dust forcing.

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Air pollution control and decreasing new particle formation lead to strong climate warming

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-25991-2011 ◽

2011 ◽

Vol 11 (9) ◽

pp. 25991-26007 ◽

Cited By ~ 2

Author(s):

R. Makkonen ◽

A. Asmi ◽

V.-M. Kerminen ◽

M. Boy ◽

A. Arneth ◽

...

Keyword(s):

Air Pollution ◽

Pollution Control ◽

Cloud Condensation Nuclei ◽

Particle Formation ◽

Control Measures ◽

Air Pollution Control ◽

New Particle Formation ◽

Anthropogenic Aerosol ◽

Aerosol Forcing ◽

Year 2000

Abstract. The number of cloud droplets determines several climatically relevant cloud properties. A major cause for the high uncertainty in the indirect aerosol forcing is the availability of cloud condensation nuclei (CCN), which in turn is highly sensitive to atmospheric new particle formation. Here we present the effect of new particle formation on anthropogenic aerosol forcing in present-day (year 2000) and future (year 2100) conditions. The total aerosol forcing (−1.61 W m−2 in year 2000) is simulated to be greatly reduced in the future, to −0.23 W m−2, mainly due to decrease in SO2 emissions and resulting decrease in new particle formation. With the total aerosol forcing decreasing in response to air pollution control measures taking effect, warming from increased greenhouse gas concentrations can potentially increase at a very rapid rate.

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Human influence strengthens the contrast between tropical wet and dry regions

10.5194/egusphere-egu2020-16966 ◽

2020 ◽

Author(s):

Andrew Schurer ◽

Gabriele Hegerl ◽

Andrew Ballinger ◽

Andrew Friedman

Keyword(s):

Climate Models ◽

Climate Model ◽

Reanalysis Data ◽

Ensemble Member ◽

Anthropogenic Aerosol ◽

In Situ Data ◽

Aerosol Forcing ◽

External Forcings ◽

Aerosol Effects ◽

The Tropics

Climate models predict a strengthening contrast between wet and dry regions in the tropics and subtropics (30&#176;S-30&#176;N), and data from the latest model intercomparison project (CMIP6) support this expectation. Rainfall in ascending regions increases, and in descending regions decreases in both climate model and reanalysis data. This strengthening contrast can be captured by tracking rainfall change each month in the wettest and driest third of the tropics and subtropics combined. Since wet and dry regions are selected individually for each model ensemble member, and the observations, and for each month, this analysis is largely unaffected by biases in location of precipitation features. Blended satellite and in situ data support the model-simulated tendency to sharpening contrasts between wet and dry regions, with rainfall in wet regions increasing substantially contrasted by a slight decrease in dry regions. These new datasets allow us to detect with more confidence the effect of external forcings on these changes, attribute them for the first time to the response to anthropogenic and natural forcings separately, and determine that the observed trends are statistically larger than the model responses. Our results show that the observed change is best explained by increasing greenhouse gases with natural forcing contributing some increase following the drop in wet region precipitation after Mount Pinatubo, while anthropogenic aerosol effects are expected to show a weak tropic-wide trend at the present time of flat global aerosol forcing. As expected from climate models, the observed signal strengthens further when focusing on the wet tail of spatial distributions in both models and data.

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Comparison of Climate Response to Anthropogenic Aerosol versus Greenhouse Gas Forcing: Distinct Patterns

Journal of Climate ◽

10.1175/jcli-d-16-0106.1 ◽

2016 ◽

Vol 29 (14) ◽

pp. 5175-5188 ◽

Cited By ~ 38

Author(s):

Hai Wang ◽

Shang-Ping Xie ◽

Qinyu Liu

Keyword(s):

Northern Hemisphere ◽

Radiative Forcing ◽

Climate Model ◽

East Asian Monsoon ◽

Climate Response ◽

Anthropogenic Aerosols ◽

Anthropogenic Aerosol ◽

Asian Monsoon Region ◽

Surface Temperature Change ◽

Aerosol Forcing

Abstract Spatial patterns of climate response to changes in anthropogenic aerosols and well-mixed greenhouse gases (GHGs) are investigated using climate model simulations for the twentieth century. The climate response shows both similarities and differences in spatial pattern between aerosol and GHG runs. Common climate response between aerosol and GHG runs tends to be symmetric about the equator. This work focuses on the distinctive patterns that are unique to the anthropogenic aerosol forcing. The tropospheric cooling induced by anthropogenic aerosols is locally enhanced in the midlatitude Northern Hemisphere with a deep vertical structure around 40°N, anchoring a westerly acceleration in thermal wind balance. The aerosol-induced negative radiative forcing in the Northern Hemisphere requires a cross-equatorial Hadley circulation to compensate interhemispheric energy imbalance in the atmosphere. Associated with a southward shift of the intertropical convergence zone, this interhemispheric asymmetric mode is unique to aerosol forcing and absent in GHG runs. Comparison of key climate response pattern indices indicates that the aerosol forcing dominates the interhemispheric asymmetric climate response in historical all-forcing simulations, as well as regional precipitation change such as the drying trend over the East Asian monsoon region. While GHG forcing dominates global mean surface temperature change, its effect is on par with and often opposes the aerosol effect on precipitation, making it difficult to detect anthropogenic change in rainfall from historical observations.

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Examining the respective roles of greenhouse-gas and aerosol forcing for modes of multi-decadal variability

10.5194/egusphere-egu2020-16250 ◽

2020 ◽

Author(s):

Andrea Dittus ◽

Ed Hawkins ◽

Laura Wilcox ◽

Dan Hodson ◽

Jon Robson ◽

...

Keyword(s):

Greenhouse Gas ◽

Large Scale ◽

Climate Model ◽

Decadal Variability ◽

Climate Projections ◽

Anthropogenic Aerosol ◽

Multidecadal Variability ◽

Aerosol Forcing ◽

Early Results ◽

Wide Range

The respective roles of aerosol and greenhouse-gas forcing in modulating the phasing and amplitude of large-scale modes of multi-decadal variability remain poorly understood, despite the attention that has been devoted to trying to separate the influence of forcing from internal variability in modes such as the Atlantic Multidecadal Variability and the Pacific Decadal Oscillation, for instance. However, understanding what drives multidecadal variability in these basins is imperative for improving near-term climate projections.Here, we show how aerosol and greenhouse-gas forcing interact with internal climate variability to generate indices of multi-decadal variability in the Atlantic, using a large ensemble of historical simulations with HadGEM3-GC3.1 for the period 1850-2014, where anthropogenic aerosol emissions are scaled to sample a wide range in historical aerosol forcing. These results are complemented by early results from new stabilised warming simulations with the same climate model and analysis of future projections from models partaking in the Sixth Phase of the Coupled Model Intercomparison Project (CMIP6).

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The Effects of Anthropogenic Aerosol Emissions from Chile and Mexico in ECHAM-HAMMOZ

10.5194/egusphere-egu2020-9976 ◽

2020 ◽

Author(s):

Tuuli Miinalainen ◽

Harri Kokkola ◽

Kari E. J. Lehtinen ◽

Thomas Kühn

Keyword(s):

Climate Model ◽

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Radiative Properties ◽

Reference Scenario ◽

Climatic Effects ◽

Anthropogenic Aerosol ◽

Regional Effect ◽

Radiative Balance ◽

Aerosol Emissions

In this research project we studied the climatic effects of anthropogenic aerosol emissions originating from Chile and Mexico. In particular, we studied black carbon (BC), organic carbon (OC) and sulfur dioxide (SO2).By using aerosol-climate model ECHAM6.3.0-HAM2.3-MOZ1.0, we analyzed how each aerosol species affects the local cloud properties and radiative balance in the atmosphere. As we here are interested in the maximum impact, we simulated each aerosol species with separate model runs. The reference scenario (BASE) was simulated with the full representation of anthropogenic aerosol emissions from the ECLIPSEV6a emission inventory for the year 2015.Then, we constructed otherwise identical scenarios but the anthropogenic aerosol emissions from Chile and Mexico for each aerosol type were removed (NO_BC, NO_OC and NO_SO2).&#160;The results indicate that for Chile the sulfur emissions seem to have the greatest impact on both cloud condensation nuclei (CCN) and cloud droplet number concentration. This result is plausible since there the SO2 emissions are much higher than BC and OC emissions. For Mexico, the OC emissions had the most notable effect on CCN, but the cloud droplets are more affected by the SO2 emissions. When looking at the radiative properties, we found out that the direct effects were rather minor compared to semi-direct and indirect effects. This indicates that aerosol-cloud interactions have much larger regional effect on radiation than the aerosol direct effect.

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Coupling aerosols to (cirrus) clouds in the global EMAC-MADE3 aerosol–climate model

Geoscientific Model Development ◽

10.5194/gmd-13-1635-2020 ◽

2020 ◽

Vol 13 (3) ◽

pp. 1635-1661 ◽

Cited By ~ 2

Author(s):

Mattia Righi ◽

Johannes Hendricks ◽

Ulrike Lohmann ◽

Christof Gerhard Beer ◽

Valerian Hahn ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Radiative Forcing ◽

Climate Model ◽

Cloud Droplet ◽

Cirrus Clouds ◽

Liquid Water Path ◽

Coupled Models ◽

Anthropogenic Aerosol ◽

Intergovernmental Panel ◽

New Model

Abstract. A new cloud microphysical scheme including a detailed parameterization for aerosol-driven ice formation in cirrus clouds is implemented in the global ECHAM/MESSy Atmospheric Chemistry (EMAC) chemistry–climate model and coupled to the third generation of the Modal Aerosol Dynamics model for Europe adapted for global applications (MADE3) aerosol submodel. The new scheme is able to consistently simulate three regimes of stratiform clouds – liquid, mixed-, and ice-phase (cirrus) clouds – considering the activation of aerosol particles to form cloud droplets and the nucleation of ice crystals. In the cirrus regime, it allows for the competition between homogeneous and heterogeneous freezing for the available supersaturated water vapor, taking into account different types of ice-nucleating particles, whose specific ice-nucleating properties can be flexibly varied in the model setup. The new model configuration is tuned to find the optimal set of parameters that minimizes the model deviations with respect to observations. A detailed evaluation is also performed comparing the model results for standard cloud and radiation variables with a comprehensive set of observations from satellite retrievals and in situ measurements. The performance of EMAC-MADE3 in this new coupled configuration is in line with similar global coupled models and with other global aerosol models featuring ice cloud parameterizations. Some remaining discrepancies, namely a high positive bias in liquid water path in the Northern Hemisphere and overestimated (underestimated) cloud droplet number concentrations over the tropical oceans (in the extratropical regions), which are both a common problem in these kinds of models, need to be taken into account in future applications of the model. To further demonstrate the readiness of the new model system for application studies, an estimate of the anthropogenic aerosol effective radiative forcing (ERF) is provided, showing that EMAC-MADE3 simulates a relatively strong aerosol-induced cooling but within the range reported in the Intergovernmental Panel on Climate Change (IPCC) assessments.

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Sensitivity of tropospheric chemical composition to halogen-radical chemistry using a fully coupled size-resolved multiphase chemistry/global climate system – Part 1: Halogen distributions, aerosol composition, and sensitivity of climate-relevant gases

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-6067-2013 ◽

2013 ◽

Vol 13 (3) ◽

pp. 6067-6129 ◽

Cited By ~ 1

Author(s):

M. S. Long ◽

W.C. Keene ◽

R. C. Easter ◽

R. Sander ◽

X. Liu ◽

...

Keyword(s):

Boundary Layer ◽

Planetary Boundary Layer ◽

Atmospheric Chemistry ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Tropospheric Chemistry ◽

Oxidation Products ◽

Aerosol Composition ◽

Mixing Ratios

Abstract. Observations and model studies suggest a significant but highly non-linear role for halogens, primarily Cl and Br, in multiphase atmospheric processes relevant to tropospheric chemistry and composition, aerosol evolution, radiative transfer, weather, and climate. The sensitivity of global atmospheric chemistry to the production of marine aerosol and the associated activation and cycling of inorganic Cl and Br was tested using a size-resolved multiphase coupled chemistry/global climate model (National Center for Atmospheric Research's Community Atmosphere Model (CAM); v3.6.33). Simulation results showed strong meridional and vertical gradients in Cl and Br species. The simulation reproduced most available observations with reasonable confidence permitting the formulation of potential mechanisms for several previously unexplained halogen phenomena including the enrichment of Br− in submicron aerosol, and the presence of a BrO maximum in the polar free troposphere. However, simulated total volatile Br mixing ratios were generally high in the troposphere. Br in the stratosphere was lower than observed due to the lack of long-lived organobromine species in the simulation. Comparing simulations using chemical mechanisms with and without reactive Cl and Br species demonstrated a significant temporal and spatial sensitivity of primary atmospheric oxidants (O3, HOx, NOx), CH4, and non-methane hydrocarbons (NMHC's) to halogen cycling. Simulated O3 and NOx were globally lower (65% and 35%, respectively, less in the planetary boundary layer based on median values) in simulations that included halogens. Globally, little impact was seen in SO2 and non-sea-salt SO42− processing due to halogens. Significant regional differences were evident: the lifetime of nss-SO42− was extended downwind of large sources of SO2. The burden and lifetime of DMS (and its oxidation products) were lower by a factor of 5 in simulations that included halogens, versus those without, leading to a 20% reduction in nss-SO42− in the Southern Hemisphere planetary boundary layer based on median values.

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