Supplementary material to "Evaluating the simulated radiative forcings, aerosol properties and stratospheric warmings from the 1963 Agung, 1982 El Chichón and 1991 Mt Pinatubo volcanic aerosol clouds"

Abstract. Accurately quantifying volcanic impacts on climate is a key requirement for robust attribution of anthropogenic climate change. Here we use the Unified Model – United Kingdom Chemistry and Aerosol (UM-UKCA) composition–climate model to simulate the global dispersion of the volcanic aerosol clouds from the three largest eruptions of the 20th century: 1963 Mt Agung, 1982 El Chichón, and 1991 Mt Pinatubo. The model has interactive stratospheric chemistry and aerosol microphysics, with coupled aerosol–radiation interactions for realistic composition–dynamics feedbacks. Our simulations align with the design of the Interactive Stratospheric Aerosol Model Intercomparison (ISA-MIP) “Historical Eruption SO2 Emissions Assessment”. For each eruption, we perform three-member ensemble model experiments for upper, mid-point, and lower estimates of SO2 emission, each re-initialised from a control run to approximately match the observed transition in the phase of the quasi-biennial oscillation (QBO) in the 6 months after the eruptions. With this experimental design, we assess how each eruption's emitted SO2 translates into a tropical reservoir of volcanic aerosol and analyse the subsequent dispersion to mid-latitudes. We compare the simulations to the volcanic forcing datasets (e.g. Space-based Stratospheric Aerosol Climatology (GloSSAC); Sato et al., 1993, and Ammann et al., 2003) that are used in historical integrations for the two most recent Coupled Model Intercomparison Project (CMIP) assessments. For Pinatubo and El Chichón, we assess the vertical extent of the simulated volcanic clouds by comparing modelled extinction to the Stratospheric Aerosol and Gas Experiment (SAGE-II) v7.0 satellite measurements and to 1964–1965 Northern Hemisphere ground-based lidar measurements for Agung. As an independent test for the simulated volcanic forcing after Pinatubo, we also compare simulated shortwave (SW) and longwave (LW) top-of-the-atmosphere radiative forcings to the flux anomalies measured by the Earth Radiation Budget Experiment (ERBE) satellite instrument. For the Pinatubo simulations, an injection of 10 to 14 Tg SO2 gives the best match to the High Resolution Infrared Sounder (HIRS) satellite-derived global stratospheric sulfur burden, with good agreement also with SAGE-II mid-visible and near-infra-red extinction measurements. This 10–14 Tg range of emission also generates a heating of the tropical stratosphere that is consistent with the temperature anomaly present in the ERA-Interim reanalysis. For El Chichón, the simulations with 5 and 7 Tg SO2 emission give best agreement with the observations. However, these simulations predict a much deeper volcanic cloud than represented in the GloSSAC dataset, which is largely based on an interpolation between Stratospheric Aerosol Measurements (SAM-II) satellite and aircraft measurements. In contrast, these simulations show much better agreement during the SAGE-II period after October 1984. For 1963 Agung, the 9 Tg simulation compares best to the forcing datasets with the model capturing the lidar-observed signature of the altitude of peak extinction descending from 20 km in 1964 to 16 km in 1965. Overall, our results indicate that the downward adjustment to SO2 emission found to be required by several interactive modelling studies when simulating Pinatubo is also needed when simulating the Agung and El Chichón aerosol clouds. This strengthens the hypothesis that interactive stratospheric aerosol models may be missing an important removal or re-distribution process (e.g. effects of co-emitted ash) which changes how the tropical reservoir of volcanic aerosol evolves in the initial months after an eruption. Our model comparisons also identify potentially important inhomogeneities in the CMIP6 dataset for all three eruption periods that are hard to reconcile with variations predicted in the interactive stratospheric aerosol simulations. We also highlight large differences between the CMIP5 and CMIP6 volcanic aerosol datasets for the Agung and El Chichón periods. Future research should aim to reduce this uncertainty by reconciling the datasets with additional stratospheric aerosol observations.

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Effect of volcanic aerosol on stratospheric NO2 and N2O5 from 2002–2014 as measured by Odin-OSIRIS and Envisat-MIPAS

10.5194/acp-2016-242 ◽

2016 ◽

Author(s):

Cristen Adams ◽

Adam E. Bourassa ◽

Chris A. McLinden ◽

Chris E. Sioris ◽

Thomas von Clarmann ◽

...

Keyword(s):

Infrared Imaging ◽

Pearson Correlation ◽

Michelson Interferometer ◽

Correlation Coefficients ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Volcanic Aerosol ◽

Quasi Biennial Oscillation ◽

El Chichón ◽

El Chichon

Abstract. Following the large volcanic eruptions of Pinatubo in 1991 and El Chichón in 1982, decreases in stratospheric NO2 associated with enhanced aerosol were observed. The Optical Spectrograph and InfraRed Imaging Spectrometer (OSIRIS) likewise measured widespread enhancements of stratospheric aerosol following seven volcanic eruptions between 2002 and 2014, although the magnitudes of these eruptions were all much smaller than the Pinatubo and El Chichón eruptions. In order to isolate and quantify the relationship between volcanic aerosol and NO2, NO2 anomalies were calculated using measurements from OSIRIS and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). In the tropics, variability due to the quasi-biennial oscillation was subtracted from the timeseries. OSIRIS profile measurements indicate that the strongest relationships between NO2 and volcanic aerosol extinction were for the layer ~ 3–7 km above the tropopause, where OSIRIS stratospheric NO2 partial columns for ~ 3–7 km above the tropopause were found to be smaller than baseline levels during these aerosol enhancements by up to ~ 60 % with typical Pearson correlation coefficients of R ~ −0.7. MIPAS also observed decreases in NO2 partial columns during periods of affected by volcanic aerosol, with percent differences of up to ~ 25 %. An even stronger relationship was observed between OSIRIS aerosol optical depth and MIPAS N2O5 partial columns, with R ~ −0.9, although no link with MIPAS HNO3 was observed. The variation of OSIRIS NO2 with increasing aerosol was found to be quantitatively consistent with simulations from a photochemical box model in terms of both magnitude and degree of non-linearity.

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Effect of volcanic aerosol on stratospheric NO2 and N2O5 from 2002–2014 as measured by Odin-OSIRIS and Envisat-MIPAS

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-8063-2017 ◽

2017 ◽

Vol 17 (13) ◽

pp. 8063-8080 ◽

Cited By ~ 5

Author(s):

Cristen Adams ◽

Adam E. Bourassa ◽

Chris A. McLinden ◽

Chris E. Sioris ◽

Thomas von Clarmann ◽

...

Keyword(s):

Infrared Imaging ◽

Pearson Correlation ◽

Michelson Interferometer ◽

Correlation Coefficients ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Volcanic Aerosol ◽

Quasi Biennial Oscillation ◽

El Chichón ◽

El Chichon

Abstract. Following the large volcanic eruptions of Pinatubo in 1991 and El Chichón in 1982, decreases in stratospheric NO2 associated with enhanced aerosol were observed. The Optical Spectrograph and Infrared Imaging Spectrometer (OSIRIS) measured the widespread enhancements of stratospheric aerosol following seven volcanic eruptions between 2002 and 2014, although the magnitudes of these eruptions were all much smaller than the Pinatubo and El Chichón eruptions. In order to isolate and quantify the relationship between volcanic aerosol and NO2, NO2 anomalies were calculated using measurements from OSIRIS and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). In the tropics, variability due to the quasi-biennial oscillation was subtracted from the time series. OSIRIS profile measurements indicate that the strongest anticorrelations between NO2 and volcanic aerosol extinction were for the 5 km layer starting ∼  3 km above the climatological mean tropopause at the given latitude. OSIRIS stratospheric NO2 partial columns in this layer were found to be smaller than background NO2 levels during these aerosol enhancements by up to ∼  60 % with typical Pearson correlation coefficients of R ∼ −0. 7. MIPAS also observed decreases in NO2 partial columns during periods affected by volcanic aerosol, with percent differences of up to ∼  25 % relative to background levels. An even stronger anticorrelation was observed between OSIRIS aerosol optical depth and MIPAS N2O5 partial columns, with R ∼ −0. 9, although no link with MIPAS HNO3 was observed. The variation in OSIRIS NO2 with increasing aerosol was found to be consistent with simulations from a photochemical box model within the estimated model uncertainty.

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Evaluating the simulated radiative forcings, aerosol properties and stratospheric warmings from the 1963 Agung, 1982 El Chichón and 1991 Mt Pinatubo volcanic aerosol clouds

10.5194/acp-2020-344 ◽

2020 ◽

Author(s):

Sandip S. Dhomse ◽

Graham W. Mann ◽

Juan Carlos Antuña Marrero ◽

Sarah E. Shallcross ◽

Martyn P. Chipperfield ◽

...

Keyword(s):

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Volcanic Aerosol ◽

Model Intercomparison ◽

Tropical Reservoir ◽

So2 Emission ◽

Aerosol Model ◽

Volcanic Forcing ◽

El Chichón ◽

El Chichon

Abstract. Accurate quantification of the effects of volcanic eruptions on climate is a key requirement for better attribution of anthropogenic climate change. Here we use the UM-UKCA composition-climate model to simulate the atmospheric evolution of the volcanic aerosol clouds from the three largest eruptions of the 20th century: 1963 Agung, 1982 El Chichón and 1991 Pinatubo. The model has interactive stratospheric chemistry and aerosol microphysics, with coupled aerosol–radiation interactions for realistic composition-dynamics feedbacks. Our simulations align with the design of the Interactive Stratospheric Aerosol Model Intercomparison (ISA-MIP) Historical Eruption SO2 Emissions Assessment. For each eruption, we perform 3-member ensemble model experiments with upper, mid-point and lower estimates for SO2 emission, each initialised to a meteorological state to match the observed phase of the quasi-biennial oscillation (QBO) at the times of the eruptions. We assess how each eruption's emitted SO2 evolves into a tropical reservoir of volcanic aerosol and analyse the subsequent dispersion to mid-latitudes. We compare the simulations to the three volcanic forcing datasets used in historical integrations for the two most recent Coupled Model Intercomparison Project (CMIP) assessments: the Global Space-based Stratospheric Aerosol Climatology (GloSSAC) for CMIP6, and the Sato et al. (1993) and Ammann et al. (2003) datasets used in CMIP5. We also assess the vertical extent of the volcanic aerosol clouds by comparing simulated extinction to Stratospheric Aerosol and Gas Experiment II (SAGE-II) v7.0 satellite aerosol data (1985–1995) for Pinatubo and El Chichón, and to 1964–65 northern hemisphere ground-based lidar measurements for Agung. As an independent test for the simulated volcanic forcing after Pinatubo, we also compare to the shortwave (SW) and longwave (LW) Top-of-the-Atmosphere flux anomalies measured by the Earth Radiation Budget Experiment (ERBE) satellite instrument. For the Pinatubo simulations, an injection of 10 to 14 Tg SO2 gives the best match to the High Resolution Infrared Sounder (HIRS) satellite-derived global stratospheric sulphur burden, with good agreement also to SAGE-II mid-visible and near-infrared extinction measurements. This 10–14 Tg range of emission also generates a heating of the tropical stratosphere that is comparable with the temperature anomaly seen in the ERA-Interim reanalyses. For El Chichón the simulations with 5 Tg and 7 Tg SO2 emission give best agreement with the observations. However, these runs predict a much deeper volcanic cloud than present in the CMIP6 data, with much higher aerosol extinction than the GloSSAC data up to October 1984, but better agreement during the later SAGE-II period. For 1963 Agung, the 9 Tg simulation compares best to the forcing datasets with the model capturing the lidar-observed signature of peak extinction descending from 20 km in 1964 to 16 km in 1965. Overall, our results indicate that the downward adjustment to previous SO2 emission estimates for Pinatubo as suggested by several interactive modelling studies is also needed for the Agung and El Chichón aerosol clouds. This strengthens the hypothesis that interactive stratospheric aerosol models may be missing an important removal or redistribution process (e.g. effects of co-emitted ash) which changes how the tropical reservoir of volcanic aerosol evolves in the initial months after an eruption. Our analysis identifies potentially important inhomogeneities in the CMIP6 dataset for all three periods that are hard to reconcile with variations predicted by the interactive stratospheric aerosol model. We also highlight large differences between the CMIP5 and CMIP6 volcanic aerosol datasets for the Agung and El Chichón periods. Future research should aim to reduce this uncertainty by reconciling the datasets with additional stratospheric aerosol observations.

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GLOBAL TRANSPORT OF VOLCANIC AEROSOL FROM EL CHICHON ERUPTION STUDIED WITH A THREE-DIMENSIONAL CIRCULATION MODEL

Geofísica Internacional ◽

10.22201/igeof.00167169p.1984.23.3.1161 ◽

1984 ◽

Vol 23 (3) ◽

pp. 415-431

Author(s):

G. PITARI ◽

G. VISCONTI

Keyword(s):

Three Dimensional ◽

Circulation Model ◽

Volcanic Aerosol ◽

Global Transport ◽

El Chichón ◽

El Chichon

Para estudiar la dispersión global de la nube volcánica de la erupción de El Chichón utilizamos el modelo tridimensional de circulación de la estratosfera desarrollado en el MIT-GIT. El modelo dependiente del tiempo se corrió para cuatro meses hasta fines de octubre de 1982. El inicio se proporcionó mediante las mediciones de la distribución del aerosol en latitud y altitud. La comparación de los resultados con los datos experimentales hecha los días 105 y 120 a partir del comienzo de la simulación muestra una concordancia razonable, si bien la concentración resultante del modelo está recorrida hacia arriba debido a que no se toma en cuenta la velocidad de sedimentación de las partículas. Se presentan también las medias mensuales de la sección latitud-longitud de la tasa de extinción, que muestran considerable heterogeneidad. Se utilizó un código de dispersión radiativa múltiple para valorar las tasas de calentamiento introducidas por un 75% de aerosol de ácido sulfúrico. En el primer mes se predijo un aumento de hasta 2° en la temperatura.

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