Forcing of stratospheric chemistry and dynamics during the Dalton Minimum

Abstract. The response of atmospheric chemistry and climate to volcanic eruptions and a decrease in solar activity during the Dalton Minimum is investigated with the fully coupled atmosphere-ocean-chemistry general circulation model SOCOL-MPIOM covering the time period 1780 to 1840 AD. We carried out several sensitivity ensemble experiments to separate the effects of (i) reduced solar ultra-violet (UV) irradiance, (ii) reduced solar visible and near infrared irradiance, (iii) enhanced galactic cosmic ray intensity as well as less intensive solar energetic proton events and auroral electron precipitation, and (iv) volcanic aerosols. The introduced changes of UV irradiance and volcanic aerosols significantly influence stratospheric climate in the early 19th century, whereas changes in the visible part of the spectrum and energetic particles have smaller effects. A reduction of UV irradiance by 15% causes global ozone decrease below the stratopause reaching 8% in the midlatitudes at 5 hPa and a significant stratospheric cooling of up to 2 °C in the midstratosphere and to 6 °C in the lower mesosphere. Changes in energetic particle precipitation lead only to minor changes in the yearly averaged temperature fields in the stratosphere. Volcanic aerosols heat the tropical lower stratosphere allowing more water vapor to enter the tropical stratosphere, which, via HOx reactions, decreases upper stratospheric and mesospheric ozone by roughly 4%. Conversely, heterogeneous chemistry on aerosols reduces stratospheric NOx leading to a 12% ozone increase in the tropics, whereas a decrease in ozone of up to 5% is found over Antarctica in boreal winter. The linear superposition of the different contributions is not equivalent to the response obtained in a simulation when all forcing factors are applied during the DM – this effect is especially well visible for NOx/NOy. Thus, this study highlights the non-linear behavior of the coupled chemistry-climate system. Finally, we conclude that especially UV and volcanic eruptions dominate the changes in the ozone, temperature and dynamics while the NOx field is dominated by the EPP. Visible radiation changes have only very minor effects on both stratospheric dynamics and chemistry.

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Stratospheric variability and trends in IPCC model simulations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-7657-2006 ◽

2006 ◽

Vol 6 (4) ◽

pp. 7657-7695 ◽

Cited By ~ 3

Author(s):

E. C. Cordero ◽

P. M. de F. Forster

Keyword(s):

General Circulation ◽

Stratospheric Ozone ◽

Circulation Model ◽

Volcanic Eruptions ◽

Ocean General Circulation Model ◽

Cold Bias ◽

Intergovernmental Panel ◽

Large Variability ◽

Volcanic Aerosols ◽

Forcing Mechanisms

Abstract. Atmosphere and Ocean General Circulation Model (AOGCM) experiments for the Intergovernmental Panel on Climate Change Fourth Assessment Report are analyzed using both 20th and 21st century model output to better understand model variability and assess the importance of various forcing mechanisms on stratospheric trends. While models represent the climatology of the stratosphere reasonably well in comparison with NCEP reanalysis, there are biases and large variability among models. In general, AOGCMs are cooler than NCEP throughout the stratosphere, with the largest differences in the tropics. Around half the AOGCMs have a top level beneath ~2 hPa and show a significant cold bias in their upper levels (~10 hPa) compared to NCEP, suggesting that these models may have compromised simulations near 10 hPa due to a low model top or insufficient stratospheric levels. In the lower stratosphere (50 hPa), the temperature variability associated with large volcanic eruptions is either absent (in about half of the models) or the warming is overestimated in the models that do include volcanic aerosols. There is general agreement on the vertical structure of temperature trends over the last few decades, differences between models are explained by the inclusion of different forcing mechanisms, such as stratospheric ozone depletion and volcanic aerosols. However, even when human and natural forcing agents are included in the simulations, significant differences remain between observations and model trends, particularly in the upper tropical troposphere (200 hPa–100 hPa), where, since 1979, models show a warming trend and the observations a cooling trend.

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Simulation of the climate impact of Mt. Pinatubo eruption using ECHAM5 – Part 1: Sensitivity to the modes of atmospheric circulation and boundary conditions

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-757-2009 ◽

2009 ◽

Vol 9 (2) ◽

pp. 757-769 ◽

Cited By ~ 29

Author(s):

M. A. Thomas ◽

C. Timmreck ◽

M. A. Giorgetta ◽

H.-F. Graf ◽

G. Stenchikov

Keyword(s):

Boundary Conditions ◽

General Circulation ◽

Circulation Model ◽

Volcanic Eruptions ◽

Climate Impact ◽

The Philippines ◽

Climate Response ◽

Stratospheric Temperature ◽

Pinatubo Eruption ◽

Volcanic Aerosols

Abstract. The eruption of Mt. Pinatubo in the Philippines in June 1991 was one of the strongest volcanic eruptions in the 20th century and this well observed eruption can serve as an important case study to understand the subsequent weather and climate changes. In this paper, the most comprehensive simulations to date of the climate impact of Mt. Pinatubo eruption are carried out with prescribed volcanic aerosols including observed SSTs, QBO and volcanically induced ozone anomalies. This is also the first attempt to include all the known factors for the simulation of such an experiment. Here, the climate response is evaluated under different boundary conditions including one at a time, thereby, investigating the radiative and dynamical responses to individual and combined forcings by observed SSTs, QBO and volcanic effects. Two ensembles of ten members each, for unperturbed and volcanically perturbed conditions were carried out using the middle atmosphere configuration of ECHAM5 general circulation model. Our results show that the simulated climate response that may arise solely from aerosol forcing in lower stratospheric temperature is insensitive to the boundary conditions in the tropics and does not show some observed features such as the temperature signature of the QBO phases. Also, statistically significant positive anomalies in the high latitudes in NH winter of 1991/92 seen in our model simulations with prescribed observed SST and QBO phases as boundary conditions are consistent with the observations. To simulate realistically the lower stratospheric temperature response, one must include all the known factors. The pure QBO and ocean signatures in lower stratospheric temperature are simulated consistently with earlier studies. The indirect effect of the volcanic aerosols manifested as the winter warming pattern is not simulated in the ensemble mean of the experiments. Our analysis also shows that the response to El Niño conditions is very strong in the model and that it partially masks the effects due to volcanic forcing.

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Stratospheric variability and trends in models used for the IPCC AR4

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-5369-2006 ◽

2006 ◽

Vol 6 (12) ◽

pp. 5369-5380 ◽

Cited By ~ 77

Author(s):

E. C. Cordero ◽

P. M. de F. Forster

Keyword(s):

General Circulation ◽

Stratospheric Ozone ◽

Circulation Model ◽

Volcanic Eruptions ◽

Ocean General Circulation Model ◽

Cold Bias ◽

Intergovernmental Panel ◽

Large Variability ◽

Volcanic Aerosols ◽

Forcing Mechanisms

Abstract. Atmosphere and ocean general circulation model (AOGCM) experiments for the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) are analyzed to better understand model variability and assess the importance of various forcing mechanisms on stratospheric trends during the 20th century. While models represent the climatology of the stratosphere reasonably well in comparison with NCEP reanalysis, there are biases and large variability among models. In general, AOGCMs are cooler than NCEP throughout the stratosphere, with the largest differences in the tropics. Around half the AOGCMs have a top level beneath ~2 hPa and show a significant cold bias in their upper levels (~10 hPa) compared to NCEP, suggesting that these models may have compromised simulations near 10 hPa due to a low model top or insufficient stratospheric levels. In the lower stratosphere (50 hPa), the temperature variability associated with large volcanic eruptions is absent in about half of the models, and in the models that do include volcanic aerosols, half of those significantly overestimate the observed warming. There is general agreement on the vertical structure of temperature trends over the last few decades, differences between models are explained by the inclusion of different forcing mechanisms, such as stratospheric ozone depletion and volcanic aerosols. However, even when human and natural forcing agents are included in the simulations, significant differences remain between observations and model trends, particularly in the upper tropical troposphere (200 hPa–100 hPa), where, since 1979, models show a warming trend and the observations a cooling trend.

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Forcing of stratospheric chemistry and dynamics during the Dalton Minimum

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-10951-2013 ◽

2013 ◽

Vol 13 (21) ◽

pp. 10951-10967 ◽

Cited By ~ 17

Author(s):

J. G. Anet ◽

S. Muthers ◽

E. Rozanov ◽

C. C. Raible ◽

T. Peter ◽

...

Keyword(s):

Solar Activity ◽

Energetic Particle ◽

Volcanic Eruptions ◽

Particle Precipitation ◽

Modeling Tools ◽

Uv Irradiance ◽

Stratospheric Dynamics ◽

Volcanic Aerosols ◽

Energetic Particle Precipitation ◽

Dalton Minimum

Abstract. The response of atmospheric chemistry and dynamics to volcanic eruptions and to a decrease in solar activity during the Dalton Minimum is investigated with the fully coupled atmosphere–ocean chemistry general circulation model SOCOL-MPIOM (modeling tools for studies of SOlar Climate Ozone Links-Max Planck Institute Ocean Model) covering the time period 1780 to 1840 AD. We carried out several sensitivity ensemble experiments to separate the effects of (i) reduced solar ultra-violet (UV) irradiance, (ii) reduced solar visible and near infrared irradiance, (iii) enhanced galactic cosmic ray intensity as well as less intensive solar energetic proton events and auroral electron precipitation, and (iv) volcanic aerosols. The introduced changes of UV irradiance and volcanic aerosols significantly influence stratospheric dynamics in the early 19th century, whereas changes in the visible part of the spectrum and energetic particles have smaller effects. A reduction of UV irradiance by 15%, which represents the presently discussed highest estimate of UV irradiance change caused by solar activity changes, causes global ozone decrease below the stratopause reaching as much as 8% in the midlatitudes at 5 hPa and a significant stratospheric cooling of up to 2 °C in the mid-stratosphere and to 6 °C in the lower mesosphere. Changes in energetic particle precipitation lead only to minor changes in the yearly averaged temperature fields in the stratosphere. Volcanic aerosols heat the tropical lower stratosphere, allowing more water vapour to enter the tropical stratosphere, which, via HOx reactions, decreases upper stratospheric and mesospheric ozone by roughly 4%. Conversely, heterogeneous chemistry on aerosols reduces stratospheric NOx, leading to a 12% ozone increase in the tropics, whereas a decrease in ozone of up to 5% is found over Antarctica in boreal winter. The linear superposition of the different contributions is not equivalent to the response obtained in a simulation when all forcing factors are applied during the Dalton Minimum (DM) – this effect is especially well visible for NOx/NOy. Thus, this study also shows the non-linear behaviour of the coupled chemistry-climate system. Finally, we conclude that especially UV and volcanic eruptions dominate the changes in the ozone, temperature and dynamics while the NOx field is dominated by the energetic particle precipitation. Visible radiation changes have only very minor effects on both stratospheric dynamics and chemistry.

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Modelling high-latitude explosive eruptions and their atmospheric and environmental impacts

10.5194/egusphere-egu21-15780 ◽

2021 ◽

Author(s):

Herman Fuglestvedt ◽

Zhihong Zhuo ◽

Michael Sigl ◽

Matthew Toohey ◽

Michael Mills ◽

...

Keyword(s):

Environmental Impacts ◽

High Latitude ◽

Radiative Forcing ◽

General Circulation ◽

Lower Thermosphere ◽

Circulation Model ◽

Ice Cores ◽

Volcanic Eruptions ◽

Explosive Eruptions ◽

Sulphate Deposition

<p>Large explosive volcanic eruptions inject sulphur into the stratosphere where it is converted to sulphur dioxide and sulphate aerosols. Due to atmospheric circulation patterns, aerosols from high-latitude eruptions typically remain concentrated in the hemisphere in which they are injected. Eruptions in the high-latitude Northern Hemisphere could thus lead to a stronger hemispheric radiative forcing and surface climate response than tropical eruptions, a claim that is supported by a previous study based on proxy records and the coupled aerosol-general circulation model MAECHAM5-HAM. Additionally, the subsequent surface deposition of volcanic sulphate is potentially harmful to humans and ecosystems, and an improved understanding of the deposition over polar ice sheets can contribute to better reconstructions of historical volcanic forcing. On this basis, we model Icelandic explosive eruptions in a pre-industrial atmosphere, taking both volcanic sulphur and halogen loading into account. We use the fully coupled Earth system model CESM2 with the atmospheric component WACCM6, which extends to the lower thermosphere and has prognostic stratospheric aerosols and full chemistry. In order to study the volcanic impacts on the atmosphere, environment, and sulphate deposition, we vary eruption parameters such as sulphur and halogen loading, and injection altitude and season. The modelled volcanic sulphate deposition is compared to the deposition in ice cores following comparable historical eruptions. Furthermore, we evaluate the potential environmental impacts of sulphate deposition. To study inter-model differences, we also compare the CESM2-WACCM6 simulations to similar Icelandic eruption experiments simulated with MAECHAM5-HAM.&#160;</p>

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Cosmic rays linked to rapid mid-latitude cloud changes

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-10941-2010 ◽

2010 ◽

Vol 10 (22) ◽

pp. 10941-10948 ◽

Cited By ~ 14

Author(s):

B. A. Laken ◽

D. R. Kniveton ◽

M. R. Frogley

Keyword(s):

Causal Relationship ◽

General Circulation ◽

Cloud Cover ◽

Circulation Model ◽

Cosmic Ray ◽

Reanalysis Data ◽

Short Term ◽

Earth’S Climate ◽

Relationship Of ◽

Galactic Cosmic Ray

Abstract. The effect of the Galactic Cosmic Ray (GCR) flux on Earth's climate is highly uncertain. Using a novel sampling approach based around observing periods of significant cloud changes, a statistically robust relationship is identified between short-term GCR flux changes and the most rapid mid-latitude (60°–30° N/S) cloud decreases operating over daily timescales; this signal is verified in surface level air temperature (SLAT) reanalysis data. A General Circulation Model (GCM) experiment is used to test the causal relationship of the observed cloud changes to the detected SLAT anomalies. Results indicate that the anomalous cloud changes were responsible for producing the observed SLAT changes, implying that if there is a causal relationship between significant decreases in the rate of GCR flux (~0.79 GU, where GU denotes a change of 1% of the 11-year solar cycle amplitude in four days) and decreases in cloud cover (~1.9 CU, where CU denotes a change of 1% cloud cover in four days), an increase in SLAT (~0.05 KU, where KU denotes a temperature change of 1 K in four days) can be expected. The influence of GCRs is clearly distinguishable from changes in solar irradiance and the interplanetary magnetic field. However, the results of the GCM experiment are found to be somewhat limited by the ability of the model to successfully reproduce observed cloud cover. These results provide perhaps the most compelling evidence presented thus far of a GCR-climate relationship. From this analysis we conclude that a GCR-climate relationship is governed by both short-term GCR changes and internal atmospheric precursor conditions.

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Stratospheric aerosol radiative forcing simulated by the chemistry climate model EMAC using aerosol CCI satellite data

10.5194/acp-2018-330 ◽

2018 ◽

Author(s):

Christoph Brühl ◽

Jennifer Schallock ◽

Klaus Klingmüller ◽

Charles Robert ◽

Christine Bingen ◽

...

Keyword(s):

Optical Depth ◽

Radiative Forcing ◽

General Circulation ◽

Asian Summer Monsoon ◽

Michelson Interferometer ◽

Circulation Model ◽

Volcanic Eruptions ◽

Radiative Heating ◽

Tropospheric Aerosol ◽

Atmospheric Sounding

Abstract. This paper presents decadal simulations of stratospheric and tropospheric aerosol by the chemistry general circulation model EMAC constrained with satellite observations in the framework of the ESA-Aerosol-CCI project like GOMOS (Global Ozone Monitoring by Occultation of Stars) and (A)ATSR ((Advanced) Along Track Scanning Radiometer) on ENVISAT (European Environmental Satellite), and IASI (Infrared Atmospheric Sounding Interferometer) on Metop (Meteorological Operational Satellite). The EMAC simulations with modal interactive aerosol and observations by GOMOS show that sulfate particles from about 230 volcanic eruptions identified mostly from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) SO2 limb measurements dominate the interannual variability of aerosol extinction in the lower stratosphere, and of radiative forcing at the tropopause. To explain the observations, desert dust and organic and black carbon, transported to the lowermost stratosphere by the Asian summer monsoon and tropical convection, are also important. This holds also for radiative heating by aerosol in the lowermost stratosphere. Comparison with (A)ATSR total aerosol optical depth at different wavelengths and IASI dust optical depth shows that the model is able to represent stratospheric and tropospheric aerosol in a consistent way.

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The Sectional Stratospheric Sulfate Aerosol module S3A-v1 within the LMDZ general circulation model: Description and evaluation against stratospheric aerosol observations

10.5194/gmd-2017-31 ◽

2017 ◽

Author(s):

Christoph Kleinschmitt ◽

Olivier Boucher ◽

Slimane Bekki ◽

François Lott ◽

Ulrich Platt

Keyword(s):

General Circulation ◽

Circulation Model ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Climate Impacts ◽

Model Description ◽

Full Interaction ◽

Microphysical Processes ◽

Aerosol Module ◽

Aerosol Radiative Effects

Abstract. Stratospheric aerosols play an important role in the climate system by affecting the Earth's radiative budget and the capabilities to simulate them interactively within global models are continuously improving. It is important to represent accurately both aerosol microphysical and atmospheric dynamical processes because together they affect the size distribution and the residence time of the aerosol particles in the stratosphere. The newly developed LMDZ-S3A model presented in this article uses a sectional approach for sulfate particles in the stratosphere and includes all the relevant microphysical processes, allowing full interaction between aerosol radiative effects and atmospheric dynamics. It reasonably reproduces aerosol observations in periods of low (background) and high (volcanic) stratospheric sulfate loading. Thus, it may serve as a tool to study the climate impacts of volcanic eruptions, as well as the deliberate anthropogenic injection of aerosols into the stratosphere, which has been proposed as a method of geoengineering to abate global warming.

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Climate variability of the mid- and high-latitudes of the Southern Hemisphere in ensemble simulations from 1500 to 2000 AD

Climate of the Past ◽

10.5194/cp-8-373-2012 ◽

2012 ◽

Vol 8 (1) ◽

pp. 373-390 ◽

Cited By ~ 15

Author(s):

S. B. Wilmes ◽

C. C. Raible ◽

T. F. Stocker

Keyword(s):

Climate Variability ◽

Southern Hemisphere ◽

General Circulation ◽

Circulation Model ◽

Volcanic Eruptions ◽

Ocean General Circulation Model ◽

Southern Annular Mode ◽

Significant Shift ◽

External Forcing ◽

Proxy Records

Abstract. To increase the sparse knowledge of long-term Southern Hemisphere (SH) climate variability, we assess an ensemble of 4 transient simulations over the last 500 yr performed with a state-of-the-art atmosphere ocean general circulation model. The model is forced with reconstructions of solar irradiance, greenhouse gas (GHG) and volcanic aerosol concentrations. A 1990 control simulation shows that the model is able to represent the Southern Annular Mode (SAM), and to some extent the South Pacific Dipole (SPD) and the Zonal Wave 3 (ZW3). During the past 500 yr we find that SPD and ZW3 variability remain stable, whereas SAM shows a significant shift towards its positive state during the 20th century. Regional temperatures over South America are strongly influenced by changing both GHG concentrations and volcanic eruptions, whereas precipitation shows no significant response to the varying external forcing. For temperature this stands in contrast to proxy records, suggesting that SH climate is dominated by internal variability rather than external forcing. The underlying dynamics of the temperature changes generally point to a combination of several modes, thus, hampering the possibilities of regional reconstructing the modes from proxy records. The linear imprint of the external forcing is as expected, i.e. a warming for increase in the combined solar and GHG forcing and a cooling after volcanic eruptions. Dynamically, only the increase in SAM with increased combined forcing is simulated.

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Initial fate of fine ash and sulfur from large volcanic eruptions

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-9043-2009 ◽

2009 ◽

Vol 9 (22) ◽

pp. 9043-9057 ◽

Cited By ~ 88

Author(s):

U. Niemeier ◽

C. Timmreck ◽

H.-F. Graf ◽

S. Kinne ◽

S. Rast ◽

...

Keyword(s):

General Circulation ◽

Circulation Model ◽

Volcanic Eruptions ◽

Wave Radiation ◽

Substantial Impact ◽

Radiative Processes ◽

Heating And Cooling ◽

Northern Latitudes ◽

The Impact ◽

Large Volcanic Eruptions

Abstract. Large volcanic eruptions emit huge amounts of sulfur and fine ash into the stratosphere. These products cause an impact on radiative processes, temperature and wind patterns. In simulations with a General Circulation Model including detailed aerosol microphysics, the relation between the impact of sulfur and fine ash is determined for different eruption strengths and locations, one in the tropics and one in high Northern latitudes. Fine ash with effective radii between 1 μm and 15 μm has a lifetime of several days only. Nevertheless, the strong absorption of shortwave and long-wave radiation causes additional heating and cooling of ±20 K/day and impacts the evolution of the volcanic cloud. Depending on the location of the volcanic eruption, transport direction changes due to the presence of fine ash, vortices develop and temperature anomalies at ground increase. The results show substantial impact on the local scale but only minor impact on the evolution of sulfate in the stratosphere in the month after the simulated eruptions.

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