Indirect radiative forcing by ion-mediated nucleation of aerosol

Abstract. A clear understanding of particle formation mechanisms is critical for assessing aerosol indirect radiative forcing and associated climate feedback processes. Recent studies reveal the importance of ion-mediated nucleation (IMN) in generating new particles and cloud condensation nuclei (CCN) in the atmosphere. Here we implement the IMN scheme into the Community Atmosphere Model version 5 (CAM5). Our simulations show that, compared to globally averaged results based on H2SO4-H2O binary homogeneous nucleation (BHN), the presence of ionization (i.e., IMN) halves H2SO4 column burden, but increases the column integrated nucleation rate by around one order of magnitude, total particle number burden by a factor of ~3, CCN burden by ~10% (at 0.2% supersaturation) to 65% (at 1.0% supersaturation), and cloud droplet number burden by ~18%. Compared to BHN, IMN increases cloud liquid water path by 7.5%, decreases precipitation by 1.1%, and increases total cloud cover by 1.9%. This leads to an increase of total shortwave cloud radiative forcing (SWCF) by 3.67 W m−2 (more negative) and longwave cloud forcing by 1.78 W m−2 (more positive), with large spatial variations. The effect of ionization on SWCF derived from this study (3.67 W m−2) is a factor of ~3 higher that of a previous study (1.15 W m−2) based on a different ion nucleation scheme and climate model. Based on the present CAM5 simulation, the 5-yr mean impacts of solar cycle induced changes in ionization rates on CCN and cloud forcing are small (~−0.02 W m−2) but have larger inter-annual (from −0.18 to 0.17 W m−2) and spatial variations.

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Indirect radiative forcing by ion-mediated nucleation of aerosol

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-17347-2012 ◽

2012 ◽

Vol 12 (7) ◽

pp. 17347-17365

Author(s):

F. Yu ◽

G. Luo ◽

X. Liu ◽

R. C. Easter ◽

X. Ma ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Models ◽

Climate Model ◽

Cloud Condensation Nuclei ◽

Particle Formation ◽

Climate Feedback ◽

Formation Mechanisms ◽

Clear Understanding ◽

Cloud Forcing ◽

Indirect Radiative Forcing

Abstract. A clear understanding of particle formation mechanisms is critical for assessing aerosol indirect radiative forcing and associated climate feedback processes. Recent studies reveal the importance of ion-mediated nucleation (IMN) in generating new particles and cloud condensation nuclei (CCN) in the atmosphere. Here we implement for the first time a physically-based treatment of IMN into the Community Atmosphere Model version 5. Our simulations show that, compared to globally averaged results based on binary homogeneous nucleation (BHN), the presence of ionization (i.e., IMN) halves H2SO4 column burden, but increases the column integrated nucleation rate by around one order of magnitude, total particle number burden by a factor of ~3, CCN burden by ~10% (at 0.2% supersaturation) to 65% (at 1.0% supersaturation), and cloud droplet number burden by ~18%. Compared to BHN, IMN increases cloud liquid water path by 7.5%, decreases precipitation by 1.1%, and increases total cloud cover by 1.9%. This leads to an increase of total shortwave cloud radiative forcing (SWCF) by 3.67 W m−2 (more negative) and longwave cloud forcing by 1.78 W m−2 (more positive), with large spatial variations. The effect of ionization on SWCF derived from this study (3.67 W m−2) is a factor of ~3 higher that of a previous study (1.15 W m−2) based on a different ion nucleation scheme and climate model. The large sensitivity of cloud forcing to nucleation process again calls for improving representation of secondary particle formation processes and aerosol-cloud interactions in climate models.

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Simulation study on the indirect effect of sulfate on the summer climate over the eastern China monsoon region

Scientific Reports ◽

10.1038/s41598-021-87832-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Dongdong Wang ◽

Bin Zhu ◽

Hongbo Wang ◽

Li Sun

Keyword(s):

Radiative Forcing ◽

Asian Summer Monsoon ◽

Cloud Condensation Nuclei ◽

Eastern China ◽

Summer Precipitation ◽

Cloud Droplet ◽

Monsoon Region ◽

Liquid Water Path ◽

Surface Cooling ◽

Community Atmosphere Model

AbstractIn this study, we designed a sensitivity test using the half number concentration of sulfate in the nucleation calculation process to study the aerosol-cloud interaction (ACI) of sulfate on clouds, precipitation, and monsoon intensity in the summer over the eastern China monsoon region (ECMR) with the National Center for Atmospheric Research Community Atmosphere Model version 5. Numerical experiments show that the ACI of sulfate led to an approximately 30% and 34% increase in the cloud condensation nuclei and cloud droplet number concentrations, respectively. Cloud droplet effective radius below 850 hPa decreased by approximately 4% in the southern ECMR, while the total liquid water path increased by 11%. The change in the indirect radiative forcing due to sulfate at the top of the atmosphere in the ECMR during summer was − 3.74 W·m−2. The decreased radiative forcing caused a surface cooling of 0.32 K and atmospheric cooling of approximately 0.3 K, as well as a 0.17 hPa increase in sea level pressure. These changes decreased the thermal difference between the land and sea and the gradient of the sea-land pressure, leading to a weakening in the East Asian summer monsoon (EASM) and a decrease in the total precipitation rate in the southern ECMR. The cloud lifetime effect has a relatively weaker contribution to summer precipitation, which is dominated by convection. The results show that the ACI of sulfate was one possible reason for the weakening of the EASM in the late 1970s.

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Large ensemble assessment of how the global surface warming response to cumulative carbon differs for negative and positive carbon emissions

10.5194/egusphere-egu21-12718 ◽

2021 ◽

Author(s):

Negar Vakilifard ◽

Katherine Turner ◽

Ric Williams ◽

Philip Holden ◽

Neil Edwards ◽

...

Keyword(s):

Carbon Emissions ◽

Radiative Forcing ◽

Climate Model ◽

Climate Feedback ◽

Climate Response ◽

Ocean Heat Uptake ◽

Transient Climate Response ◽

Surface Warming ◽

Radiative Processes ◽

Negative Emission

The controls of the effective transient climate response (TCRE), defined in terms of the dependence of surface warming since the pre-industrial to the cumulative carbon emission, is explained in terms of climate model experiments for a scenario including positive emissions and then negative emission over a period of 400 years. We employ a pre-calibrated ensemble of GENIE, grid-enabled integrated Earth system model, consisting of 86 members to determine the process of controlling TCRE in both CO2 emissions and drawdown phases. Our results are based on the GENIE simulations with historical forcing from AD 850 including land use change, and the future forcing defined by CO2 emissions and a non-CO2 radiative forcing timeseries. We present the results for the point-source carbon capture and storage (CCS) scenario as a negative emission scenario, following the medium representative concentration pathway (RCP4.5), assuming that the rate of emission drawdown is 2 PgC/yr CO2 for the duration of 100 years. The climate response differs between the periods of positive and negative carbon emissions with a greater ensemble spread during the negative carbon emissions. The controls of the spread in ensemble responses are explained in terms of a combination of thermal processes (involving ocean heat uptake and physical climate feedback), radiative processes (saturation in radiative forcing from CO2 and non-CO2 contributions) and carbon dependences (involving terrestrial and ocean carbon uptake).&#160;&#160;

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Description and basic evaluation of simulated mean state, internal variability, and climate sensitivity in MIROC6

Geoscientific Model Development ◽

10.5194/gmd-12-2727-2019 ◽

2019 ◽

Vol 12 (7) ◽

pp. 2727-2765 ◽

Cited By ~ 58

Author(s):

Hiroaki Tatebe ◽

Tomoo Ogura ◽

Tomoko Nitta ◽

Yoshiki Komuro ◽

Koji Ogochi ◽

...

Keyword(s):

Climate Variability ◽

Climate Sensitivity ◽

Radiative Forcing ◽

Climate Model ◽

Coupled Model ◽

Climate Feedback ◽

Climate Projections ◽

Internal Climate Variability ◽

Wide Range ◽

Mean Climate

Abstract. The sixth version of the Model for Interdisciplinary Research on Climate (MIROC), called MIROC6, was cooperatively developed by a Japanese modeling community. In the present paper, simulated mean climate, internal climate variability, and climate sensitivity in MIROC6 are evaluated and briefly summarized in comparison with the previous version of our climate model (MIROC5) and observations. The results show that the overall reproducibility of mean climate and internal climate variability in MIROC6 is better than that in MIROC5. The tropical climate systems (e.g., summertime precipitation in the western Pacific and the eastward-propagating Madden–Julian oscillation) and the midlatitude atmospheric circulation (e.g., the westerlies, the polar night jet, and troposphere–stratosphere interactions) are significantly improved in MIROC6. These improvements can be attributed to the newly implemented parameterization for shallow convective processes and to the inclusion of the stratosphere. While there are significant differences in climates and variabilities between the two models, the effective climate sensitivity of 2.6 K remains the same because the differences in radiative forcing and climate feedback tend to offset each other. With an aim towards contributing to the sixth phase of the Coupled Model Intercomparison Project, designated simulations tackling a wide range of climate science issues, as well as seasonal to decadal climate predictions and future climate projections, are currently ongoing using MIROC6.

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Radiative forcing estimates of sulfate aerosol in coupled climate-chemistry models with emphasis on the role of the temporal variability

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-5583-2012 ◽

2012 ◽

Vol 12 (12) ◽

pp. 5583-5602 ◽

Cited By ~ 18

Author(s):

C. Déandreis ◽

Y. Balkanski ◽

J. L. Dufresne ◽

A. Cozic

Keyword(s):

Temporal Variability ◽

Radiative Forcing ◽

Climate Model ◽

Circulation Model ◽

Reference Method ◽

Sulfate Aerosol ◽

The Impact ◽

Net Fluxes ◽

Indirect Radiative Forcing ◽

Aerosol Radiative

Abstract. This paper describes the impact on the sulfate aerosol radiative effects of coupling the radiative code of a global circulation model with a chemistry-aerosol module. With this coupling, temporal variations of sulfate aerosol concentrations influence the estimate of aerosol radiative impacts. Effects of this coupling have been assessed on net fluxes, radiative forcing and temperature for the direct and first indirect effects of sulfate. The direct effect respond almost linearly to rapid changes in concentrations whereas the first indirect effect shows a strong non-linearity. In particular, sulfate temporal variability causes a modification of the short wave net fluxes at the top of the atmosphere of +0.24 and +0.22 W m−2 for the present and preindustrial periods, respectively. This change is small compared to the value of the net flux at the top of the atmosphere (about 240 W m−2). The effect is more important in regions with low-level clouds and intermediate sulfate aerosol concentrations (from 0.1 to 0.8 μg (SO4) m−3 in our model). The computation of the aerosol direct radiative forcing is quite straightforward and the temporal variability has little effect on its mean value. In contrast, quantifying the first indirect radiative forcing requires tackling technical issues first. We show that the preindustrial sulfate concentrations have to be calculated with the same meteorological trajectory used for computing the present ones. If this condition is not satisfied, it introduces an error on the estimation of the first indirect radiative forcing. Solutions are proposed to assess radiative forcing properly. In the reference method, the coupling between chemistry and climate results in a global average increase of 8% in the first indirect radiative forcing. This change reaches 50% in the most sensitive regions. However, the reference method is not suited to run long climate simulations. We present other methods that are simpler to implement in a coupled chemistry/climate model and that offer the possibility to assess radiative forcing.

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Surprising similarities in model and observational aerosol radiative forcing estimates

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-613-2020 ◽

2020 ◽

Vol 20 (1) ◽

pp. 613-623 ◽

Cited By ~ 11

Author(s):

Edward Gryspeerdt ◽

Johannes Mülmenstädt ◽

Andrew Gettelman ◽

Florent F. Malavelle ◽

Hugh Morrison ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Liquid Water Path ◽

Intergovernmental Panel ◽

Aerosol Radiative Forcing ◽

Aerosol Forcing ◽

Cloud Properties ◽

The Impact

Abstract. The radiative forcing from aerosols (particularly through their interaction with clouds) remains one of the most uncertain components of the human forcing of the climate. Observation-based studies have typically found a smaller aerosol effective radiative forcing than in model simulations and were given preferential weighting in the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5). With their own sources of uncertainty, it is not clear that observation-based estimates are more reliable. Understanding the source of the model and observational differences is thus vital to reduce uncertainty in the impact of aerosols on the climate. These reported discrepancies arise from the different methods of separating the components of aerosol forcing used in model and observational studies. Applying the observational decomposition to global climate model (GCM) output, the two different lines of evidence are surprisingly similar, with a much better agreement on the magnitude of aerosol impacts on cloud properties. Cloud adjustments remain a significant source of uncertainty, particularly for ice clouds. However, they are consistent with the uncertainty from observation-based methods, with the liquid water path adjustment usually enhancing the Twomey effect by less than 50 %. Depending on different sets of assumptions, this work suggests that model and observation-based estimates could be more equally weighted in future synthesis studies.

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Impact of isolated atmospheric aging processes on the cloud condensation nuclei activation of soot particles

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-15545-2019 ◽

2019 ◽

Vol 19 (24) ◽

pp. 15545-15567 ◽

Cited By ~ 2

Author(s):

Franz Friebel ◽

Prem Lobo ◽

David Neubauer ◽

Ulrike Lohmann ◽

Saskia Drossaart van Dusseldorp ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Model ◽

Cloud Condensation Nuclei ◽

Particle Diameter ◽

Cloud Droplet ◽

High Sensitivity ◽

Condensation Nuclei ◽

Soot Particles ◽

Atmospheric Aging ◽

Ccn Activity

Abstract. The largest contributors to the uncertainty in assessing the anthropogenic contribution in radiative forcing are the direct and indirect effects of aerosol particles on the Earth's radiative budget. Soot particles are of special interest since their properties can change significantly due to aging processes once they are emitted into the atmosphere. Probably the largest obstacle for the investigation of these processes in the laboratory is the long atmospheric lifetime of 1 week, requiring tailored experiments that cover this time span. This work presents results on the ability of two types of soot, obtained using a miniCAST soot generator, to act as cloud condensation nuclei (CCN) after exposure to atmospherically relevant levels of ozone (O3) and humidity. Aging times of up to 12 h were achieved by successful application of the continuous-flow stirred tank reactor (CSTR) concept while allowing for size selection of particles prior to the aging step. Particles of 100 nm diameter and rich in organic carbon (OC) that were initially CCN inactive showed significant CCN activity at supersaturations (SS) down to 0.3 % after 10 h of exposure to 200 ppb of O3. While this process was not affected by different levels of relative humidity in the range of 5 %–75 %, a high sensitivity towards the ambient/reaction temperature was observed. Soot particles with a lower OC content required an approximately 4-fold longer aging duration to show CCN activity at the same SS. Prior to the slow change in the CCN activity, a rapid increase in the particle diameter was detected which occurred within several minutes. This study highlights the applicability of the CSTR approach for the simulation of atmospheric aging processes, as aging durations beyond 12 h can be achieved in comparably small aerosol chamber volumes (<3 m3). Implementation of our measurement results in a global aerosol-climate model, ECHAM6.3-HAM2.3, showed a statistically significant increase in the regional and global CCN burden and cloud droplet number concentration.

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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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Will marine dimethylsulfide emissions amplify or alleviate global warming? A model study

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f04-045 ◽

2004 ◽

Vol 61 (5) ◽

pp. 826-835 ◽

Cited By ~ 52

Author(s):

Laurent Bopp ◽

Olivier Boucher ◽

Olivier Aumont ◽

Sauveur Belviso ◽

Jean-Louis Dufresne ◽

...

Keyword(s):

Global Warming ◽

Radiative Forcing ◽

Sulfur Compound ◽

Cloud Condensation Nuclei ◽

Regional Climate ◽

Climate Feedback ◽

Model Study ◽

Radiative Impact ◽

Radiative Perturbation ◽

First Time

Dimethylsulfide (DMS) is the most abundant volatile sulfur compound at the sea surface and has a strong marine phytoplanktonic origin. Once outgased into the atmosphere, it contributes to the formation of sulfate aerosol particles that affect the radiative budget as precursors of cloud condensation nuclei (CCN). It has been postulated that climate may be partly modulated by variations in DMS production. We test this hypothesis in the context of anthro pogenic climate change and present here, modelled for the first time, an estimate of the radiative impact resulting from changes in DMS airsea fluxes caused by global warming. At 2× CO2, our model estimates a small increase (3%) in the global DMS flux to the atmosphere but with large spatial heterogeneities (from 15% to 30%). The radiative perturbation resulting from the DMS-induced change in cloud albedo is estimated to be 0.05 W·m2, which represents only a small negative climate feedback on global warming. However, there are large regional changes, such as a perturbation of up to 1.5 W·m2 in summer between 40°S and 50°S, that can impact the regional climate. In the Southern Ocean, the radiative impact resulting from changes in the DMS cycle may partly alleviate the radiative forcing resulting from anthropogenic CO2.

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Radiative forcing estimates in coupled climate-chemistry models with emphasis on the role of the temporal variability

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-24313-2011 ◽

2011 ◽

Vol 11 (8) ◽

pp. 24313-24364 ◽

Cited By ~ 2

Author(s):

C. Déandreis ◽

Y. Balkanski ◽

J. L. Dufresne ◽

A. Cozic

Keyword(s):

Temporal Variability ◽

Radiative Forcing ◽

Climate Model ◽

Circulation Model ◽

Reference Method ◽

Sulphate Aerosol ◽

The Impact ◽

Net Fluxes ◽

Indirect Radiative Forcing ◽

Aerosol Radiative

Abstract. This paper describes the impact on the sulphate aerosol radiative effects of coupling the radiative code of a global circulation model with a chemistry-aerosol module. With this coupling, temporal variations of sulphate aerosol concentrations influence the estimate of aerosol radiative impacts. Effects of this coupling have been assessed on net fluxes, radiative forcing and temperature for direct and first indirect effects of sulphate. The direct effect responds almost linearly to rapid changes in concentrations whereas, the first indirect effect shows a strong non-linearity. In particular, sulphate temporal variability causes a large modification of the short wave net fluxes at the top of the atmosphere (+0.24 and +0.22 W m−2 for respectively, the present and preindustrial periods that are about 30 % of the total radiative forcing of sulfate). The effect is particularly important in regions with low-level clouds and intermediate sulphate aerosol concentrations (from 0.1 to 0.8 μg (SO4) m−3 in our model). If computation of the aerosol direct radiative forcing is quite straightforward and has few effects; quantifying the first indirect radiative forcing requires first to tackle technical issues. We show that preindustrial sulphate concentrations have to be calculated with the same meteorological trajectory than that used for computing present ones. If this condition is not satisfied, the error on the estimation of the first indirect radiative forcing is of 60 %. Solutions are proposed to assess radiative forcing properly. In the reference method, the coupling between chemistry and climate results in a global average increase of 8 % in the first indirect radiative forcing. This change reaches 50 % in the most sensitive regions. However, the reference method is not suited to run long climate simulations. We present other methods that are simpler to implement in a coupled chemistry/climate model and that offer the possibility to assess radiative forcing.

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