scholarly journals The impact of MISR-derived injection height initialization on wildfire and volcanic plume dispersion in the HYSPLIT model

2018 ◽  
Vol 11 (11) ◽  
pp. 6289-6307 ◽  
Author(s):  
Charles J. Vernon ◽  
Ryan Bolt ◽  
Timothy Canty ◽  
Ralph A. Kahn
Keyword(s):  
Volcanic Eruptions ◽  
Dust Storms ◽  
Volcanic Plume ◽  
Plume Dispersion ◽  
Hysplit Model ◽  
Particle Injection ◽  
Nominal Model ◽  
Satellite Retrievals ◽  
Aerosol Sources ◽  
The Impact

Abstract. The dispersion of particles from wildfires, volcanic eruptions, dust storms, and other aerosol sources can affect many environmental factors downwind, including air quality. Aerosol injection height is one source attribute that mediates downwind dispersion, as wind speed and direction can vary dramatically with elevation. Using plume heights derived from space-based, multi-angle imaging, we examine the impact of initializing plumes in the NOAA Air Resources Laboratory's Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model with satellite-measured vs. nominal (model-calculated or VAAC-reported) injection height on the simulated dispersion of six large aerosol plumes. When there are significant differences in nominal vs. satellite-derived particle injection heights, especially if both heights are in the free troposphere or if one injection height is within the planetary boundary layer (PBL) and the other is above the PBL, differences in simulation results can arise. In the cases studied with significant nominal vs. satellite-derived injection height differences, the HYSPLIT model can represent plume evolution better, relative to independent satellite observations, if the injection height in the model is constrained by hyper-stereo satellite retrievals.

scholarly journals The Impact of MISR-derived Injection Height Initialization on Wildfire and Volcanic Plume Dispersion in the HYSPLIT Model

2018 ◽  
Author(s):  
Charles J. Vernon ◽  
Ryan Bolt ◽  
Timothy Canty ◽  
Ralph A. Kahn
Keyword(s):  
Volcanic Eruptions ◽  
Dust Storms ◽  
Volcanic Plume ◽  
Plume Dispersion ◽  
Hysplit Model ◽  
Particle Injection ◽  
Nominal Model ◽  
Satellite Retrievals ◽  
Aerosol Sources ◽  
The Impact

Abstract. The dispersion of particles from wildfires, volcanic eruptions, dust storms, and other aerosol sources can affect air quality and other environmental factors downwind. Aerosol injection height is one source attribute that mediates downwind dispersion, as wind speed and direction can vary dramatically with elevation. Using plume heights derived from space-based, multi-angle imaging, we examine the impact of initializing plumes with satellite-measured vs. nominal (model-calculated or VAAC observations) injection height on the simulated dispersion of six large aerosol plumes. When there are significant differences in nominal vs. satellite-derived particle injection heights, or if one injection height is within the planetary boundary layer (PBL) and the other is above the PBL, differences in simulation results can arise. In the cases studied with significant nominal vs. satellite-derived injection height differences, the NOAA Air Resources Laboratory's Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model tends to represent plume evolution better if the injection height in the model is constrained by hyper-stereo satellite retrievals.

Revisiting the Krakatau 1883 Volcanic Aerosol Dispersal 

2021 ◽  
Author(s):  
Rafael Castro ◽  
Tushar Mittal ◽  
Stephen Self
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Volcanic Eruptions ◽  
Climate Impact ◽  
Volcanic Plume ◽  
Quasi Biennial Oscillation ◽  
Aerosol Cloud ◽  
Pinatubo Eruption ◽  
The Impact

<p>The 1883 Krakatau eruption is one of the most well-known historical volcanic eruptions due to its significant global climate impact as well as first recorded observations of various aerosol associated optical and physical phenomena. Although much work has been done on the former by comparison of global climate model predictions/ simulations with instrumental and proxy climate records, the latter has surprisingly not been studied in similar detail. In particular, there is a wealth of observations of vivid red sunsets, blue suns, and other similar features, that can be used to analyze the spatio-temporal dispersal of volcanic aerosols in summer to winter 1883. Thus, aerosol cloud dispersal after the Krakatau eruption can be estimated, bolstered by aerosol cloud behavior as monitored by satellite-based instrument observations after the 1991 Pinatubo eruption. This is one of a handful of large historic eruptions where this analysis can be done (using non-climate proxy methods). In this study, we model particle trajectories of the Krakatau eruption cloud using the Hysplit trajectory model and compare our results with our compiled observational dataset (principally using Verbeek 1884, the Royal Society report, and Kiessling 1884).</p><p>In particular, we explore the effect of different atmospheric states - the quasi-biennial oscillation (QBO) which impacts zonal movement of the stratospheric volcanic plume - to estimate the phase of the QBO in 1883 required for a fast-moving westward cloud. Since this alone is unable to match the observed latitudinal spread of the aerosols, we then explore the impact of an  umbrella cloud (2000 km diameter) that almost certainly formed during such a large eruption. A large umbrella cloud, spreading over ~18 degrees within the duration of the climax of the eruption (6-8 hours), can lead to much quicker latitudinal spread than a point source (vent). We will discuss the results of the combined model (umbrella cloud and correct QBO phase) with historical accounts and observations, as well as previous work on the 1991 Pinatubo eruption. We also consider the likely impacts of water on aerosol concentrations and the relevance of this process for eruptions with possible significant seawater interactions, like Krakatau. We posit that the role of umbrella clouds is an under-appreciated, but significant, process for beginning to model the climatic impacts of large volcanic eruptions.</p>

Impact of the Christmas 2018 Mount Etna Eruption on the Regional Air Quality

2021 ◽  
Author(s):  
Claire Lamotte ◽  
Jonathan Guth ◽  
Virginie Marécal ◽  
Giuseppe Salerno ◽  
Nicolas Theys ◽  
...  
Keyword(s):  
Air Quality ◽  
Regional Scale ◽  
Volcanic Eruptions ◽  
Mount Etna ◽  
Surface Measurement ◽  
Volcanic Plume ◽  
Observation Data ◽  
Sulfate Aerosols ◽  
Lower Altitude ◽  
The Impact

<p><span>Volcanic eruptions are events that can eject several tons of material into the atmosphere. Among these emissions, sulfur dioxide is the main sulfurous volcanic gas. It can form sulfate aerosols that are harmful to health or, being highly soluble, it can condense in water particles and form acid rain. Thus, volcanic eruptions can have an environmental impact on a regional scale.</span></p><p><span>The Mediterranean region is very interesting from this point of view because it is a densely populated region with a strong anthropogenic activity, therefore polluted, in which Mount Etna is also located. Mount Etna is the largest passive SO<sub>2</sub> emitter in Europe, but it can also sporadically produce strong eruptive events. It is then likely that the additional input of sulfur compounds into the atmosphere by volcanic emissions may have effects on the regional atmospheric sulfur composition.</span></p><p><span>We are particularly investigating the eruption of Mount Etna on December 24, 2018 [Corradini et al, 2020]. This eruption took place along a 2 km long breach on the side of the volcano, thus at a lower altitude than its main crater. About 100 kt of SO<sub>2</sub> and 35 kt of ash were released in total, between December 24 and 30. With the exception of the 24th, the quantities of ash were always lower than the SO<sub>2.</sub></span></p><p><span>The availability of the TROPOMI SO<sub>2</sub><sub></sub></span><span>column </span><span>estimates, at fine </span><span>spatial</span><span> resolution </span><span>(7 km x 3.5 km at nadir) and </span><span>associated averaging kernels</span><span>,</span><span> during this eruptive period made it also an excellent case study. </span><span>It </span><span>allow</span><span>s</span><span> us to follow the evolution of SO<sub>2</sub> in the volcanic plume over several days.</span></p><p><span>Using the CNRM MOCAGE chemistry-transport model (CTM), we aim to quantify the impact of this volcanic eruption on atmospheric composition, sulfur deposition and air quality at the regional scale. The comparison of the model with the TROPOMI observation data allows us to assess the ability of the model to properly represent the plume. In spite of a particular meteorological situation, leading to a complex plume transport, MOCAGE shows a good agreement with TROPOMI observations. Thus, from the MOCAGE simulation, we can evaluate the impact of the eruption on the regional concentrations of SO<sub>2</sub> and sulfate aerosols, but also analyse the quantities of dry and wet deposition, and compare it to surface measurement stations.</span></p>

Towards high-towards high-resolution dust reanalysis for Northern Africa, the Middle East and Europe

2020 ◽  
Author(s):  
Enza Di Tomaso ◽  
Sara Basart ◽  
Jeronimo Escribano ◽  
Paul Ginoux ◽  
Oriol Jorba ◽  
...  
Keyword(s):  
Kalman Filter ◽  
Middle East ◽  
Data Assimilation ◽  
Dust Storms ◽  
Northern Africa ◽  
Combine Model ◽  
Climate Services ◽  
Deep Blue ◽  
Satellite Retrievals ◽  
The Impact

<p>DustClim (Dust Storms Assessment for the development of user-oriented Climate Services in Northern Africa, Middle East and Europe) is a project of the European Research Area For Climate Services (ERA4CS). DustClim is aiming to provide reliable information on sand and dust storms for developing dust-related services for selected socio-economic sectors: air quality, aviation and solar energy.</p><p>This contribution will describe the work done within the DustClim project towards the production of a dust reanalysis over the domain of Northern Africa, the Middle East and Europe at an unprecedented high spatial resolution (at 10km x 10km) using the state-of-art Multiscale Online Nonhydrostatic Atmosphere Chemistry model (MONARCH) and its data assimilation capability (Di Tomaso et al., 2017). An ensemble-based Kalman filter (namely the local ensemble transform Kalman filter – LETKF) has been utilized to optimally combine model simulations and satellite retrievals.</p><p>Dust ensemble forecasts are used to estimate flow-dependent forecast uncertainty, which is used by the data assimilation scheme to optimally combine model prior information with satellite retrievals. Satellite observations from MODIS Deep Blue with specific observational constraint for dust (Ginoux et al., 2012; Pu and Ginoux, 2016; Sayer et al., 2014) are considered for assimilation over land surfaces, including source regions. MONARCH ensemble has been generated by applying multi-parameters, multi-physics, multi-meteorological initial and boundary conditions perturbations. Sensitive parameters of the assimilation configuration like the balance between observational and background uncertainty, or the spatial location of errors have been carefully calibrated.</p><p>The dust reanalysis for the period 2011-2016 is being compared against independent dust-filtered observations from AERONET (AErosol RObotic NETwork) show the benefit of the assimilation of dust-related MODIS Deep Blue products over areas not easily covered by other observational datasets. Particularly relevant is the improvement of the model skills over the Sahara.</p><p>References:<br>Di Tomaso, E., Schutgens, N. A. J., Jorba, O., and Pérez García-Pando, C. (2017): Assimilation of MODIS Dark Target and Deep Blue observations in the dust aerosol component of NMMB-MONARCH version 1.0, Geosci. Model Dev., 10, 1107-1129, doi:10.5194/gmd-10-1107-2017.<br>Ginoux, P., Prospero, J. M., Gill, T. E., Hsu, N. C. and Zhao, M. Global-Scale Attribution of Anthropogenic and Natural Dust Sources and Their Emission Rates Based on Modis Deep Blue Aerosol Products. Rev Geophys 50, doi:10.1029/2012rg000388 (2012).<br>Pu, B., and Ginoux, P. (2016). The impact of the Pacific Decadal Oscillation on springtime dust activity in Syria. Atmospheric Chemistry and Physics, 16(21), 13431-13448.<br>Sayer, A. M., Munchak, L. A., Hsu, N. C., Levy, R. C., Bettenhausen, C., and Jeong, M.-J.: MODIS Collection 6 aerosol products: Comparison between Aqua’s e-Deep Blue, Dark Target, and “merged” data sets, and usage recommendations, J. Geophys. Res.-Atmos., 119, 13965–13989, doi:10.1002/2014JD022453, 2014.</p><p>Acknowledgement<br>DustClim project is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462). We acknowledge PRACE for awarding access to HPC resources through the eDUST and eFRAGMENT1 projects.</p><p> </p>

scholarly journals OClO and BrO observations in the volcanic plume of Mt. Etna – implications on the chemistry of chlorine and bromine species in volcanic plumes

2014 ◽  
Vol 14 (18) ◽  
pp. 25213-25280
Author(s):  
J. Gliß ◽  
N. Bobrowski ◽  
L. Vogel ◽  
U. Platt
Keyword(s):  
Early Morning ◽  
Optical Absorption Spectroscopy ◽  
Volcanic Plume ◽  
Plume Dispersion ◽  
Strong Indication ◽  
Volcanic Plumes ◽  
Mixing Ratios ◽  
Rate Of Increase ◽  
Mt Etna ◽  
The Impact

Abstract. Spatial and temporal profiles of chlorine dioxide (OClO), bromine monoxide (BrO) and sulphur dioxide (SO2) were measured in the plume of Mt. Etna, Italy, in September 2012 using Multi-Axis-Differential-Optical-Absorption-Spectroscopy (MAX-DOAS). OClO (BrO) was detected in 119 (452) individual measurements covering plume ages up to 6 (23) minutes. The retrieved slant column densities (SCDs) reached values up to 2.0 × 1014 molecules cm−2 (OClO) and 1.1 × 1015 molecules cm−2 (BrO). In addition, the spectra were analysed for signatures of IO, OIO and OBrO, none of these species could be detected. The corresponding detection limits for IO / SO2, OIO / SO2 and OBrO / SO2 were 1.8 × 10−6, 2.0 × 10−5 and 1.1 × 10−5 respectively. The measurements were performed at plume ages (τ) from zero to 23 min downwind the emission source. The chemical variability of BrO and OClO in the plume was studied analysing the OClO / SO2 and BrO / SO2-ratio. A marked increase of both ratios was observed in the young plume (τ < 3 min) and a levelling off at larger plume ages (τ > 3 min) with mean abundances of 3.17 × 10−5 (OClO / SO2), 1.55 × 10−4 (BrO / SO2) and 0.16 (OClO / BrO). Furthermore, enhanced BrO/SO2-ratios were found at the plume edges (by ~30–37%) and a strong indication of enhanced OClO / SO2-ratios as well (~10–250%). A measurement performed in the early morning (05:20–06:20 UTC, sunrise: 04:40 UTC) showed an BrO / SO2-ratio increasing with time until 05:35 UTC and a constant ratio afterwards. Observing this increase was only possible due to a correction for stratospheric BrO signals in the plume spectra. The corresponding OClO / SO2-ratio showed a similar trend stabilising around 06:13 UTC, approximately 40 min later than BrO. This is another strong indication for the photochemical nature of the reactions involved in the formation of oxidised halogens in volcanic plumes. In particular, these findings support the current understanding of the underlying chemistry, namely, that BrO is formed in an autocatalytic reaction mechanism in literature often referred to as "bromine explosion" and that OClO is formed in the "BrO + ClO"-reaction. BrO and OClO concentrations were estimated from the measured SCDs assuming a circular plume shape. In addition, mixing ratios of ClO were determined from the retrieved OClO and BrO-SCDs assuming chemical equilibrium between formation of OClO (BrO + ClO) and its destruction (photolysis). Mean abundances in the young plume (τ<4 min) were BrO = 1.35 ppb, OClO = 300 ppt and ClO = 139 ppt with peak values of 600 ppt (OClO), 2.7 ppb (BrO) and 235 ppt (ClO) respectively. The prevailing Cl-atom concentrations in the plume could be estimated from the rate of increase of OClO and BrO in the young plume and the determined ClO and OClO concentrations. Values between 5.1 × 106 cm−3 (at 40 ppb O3) and 2.1 × 108 cm−3 (at 1 ppb O3) were found. Based on that, a potential – chlorine induced – depletion of tropospheric methane (CH4) in the plume was investigated. CH4-lifetimes between 13 h (at 1 ppb O3) and 23 days (at 40 ppb O3) were found. These are considerably small compared to the atmospheric lifetime of CH4. However, the impact of gaseous chlorine on the CH4-budget in the plume environment was assessed to be relatively small, mainly due to plume dispersion (decrease of Cl number densities) and permanent mixing of the plume with the surrounding atmosphere (net supply of O3 and CH4).

New strategies for chemistry-transport modelling of volcanic plumes: application to the case of Mount Etna eruption in March 18, 2012

2020 ◽  
Author(s):  
Mathieu Lachatre ◽  
Sylvain Mailler ◽  
Laurent Menut ◽  
Solene Turquety ◽  
Pasquale Sellitto ◽  
...  
Keyword(s):  
Wind Field ◽  
Substantial Reduction ◽  
Vertical Direction ◽  
Volcanic Eruptions ◽  
Vertical Wind ◽  
Mount Etna ◽  
Volcanic Plume ◽  
Large Spatial Scale ◽  
Numerical Diffusion ◽  
The Impact

&lt;p&gt;Atmospheric modelling allows to study large spatial scale events such as volcanic eruptions, which can emit large amounts of plume-confined particulate matter and gases, to evaluate their transport in the atmosphere and their subsequent impacts. However, to study more precisely these events, different issues have to be addressed. One notable example of these issues is the well-known excessive numerical diffusion in the atmospheric column in Eulerian models leading to excessive plume dispersion misrepresentation of the plume three-dimensional morphology and subsequent geographical extent of its impacts. Mount Etna volcano&amp;#8217;s moderate eruption of March 18, 2012, which released about 3kT of sulphure dioxide in the atmosphere, has been simulated in this study with the CHIMERE chemistry-transport model. The simulated plume has been observed and tracked with satellite instruments (OMI and IASI) for several days during its transport over the Mediterranean Sea in order to compare with model outputs.&lt;/p&gt;&lt;p&gt;Sensitivity tests have been performed to evaluate the impact of injection altitude and profile shape on the subsequent trajectory of the plume. It was shown that altitude is the most sensitive parameter when results remain weakly sensitive to the vertical shape of injection.&lt;/p&gt;&lt;p&gt;In order to effectively address the problem of excessive numerical diffusion, we have included a new antidiffusive transport scheme in the vertical direction and a new strategy to use directly the vertical wind field provided by the forcing meteorological model. We show that both these improvements permit a substantial reduction in numerical diffusion. The use of the new antidiffusive vertical scheme has brought the strongest improvement in our model outputs. To a lesser extent, a more realistic representation of the vertical wind field has also been shown to reduce volcanic plume spreading. In summary, we show that these two improvements bring an improvement in the representation of the plume which is as strong as the improvement brought by increasing the number of vertical levels, but without an additional burden in computational power.&lt;/p&gt;&lt;p&gt;This study has been supported by AID (Agence de l'Innovation de D&amp;#233;fense) under grant TROMPET.&lt;/p&gt;

scholarly journals Aerosol properties and meteorological conditions in the city of Buenos Aires, Argentina during the resuspension of volcanic ash from the Puyehue-Cordón Caulle eruption

2016 ◽  
Author(s):  
A. G. Ulke ◽  
M. M. Torres Brizuela ◽  
G. B. Raga ◽  
D. Baumgardner
Keyword(s):  
Volcanic Ash ◽  
Buenos Aires ◽  
Volcanic Eruptions ◽  
Meteorological Conditions ◽  
Dust Storms ◽  
Volcanic Complex ◽  
Strong Wind ◽  
Hysplit Model ◽  
The City ◽  
Aerosol Properties

Abstract. The eruption in June 2011 of the Puyehue-Cordón Caulle Volcanic Complex in Chile impacted air traffic around the Southern Hemisphere for several months after the initial ash emissions. The ash deposited in vast areas of the Patagonian steppe was subjected to the strong wind conditions prevalent during the austral winter and spring, experiencing resuspension over various regions of Argentina. In this study we analyze the meteorological conditions that led to the episode of volcanic ash resuspension, which impacted the city of Buenos Aires and resulted in the closure of both airports on 16 October 2011. The thermodynamic soundings show the signature of "pulses of drying" associated with the presence of hygroscopic ash in the atmosphere that has been reported in similar episodes after volcanic eruptions in other parts of the world. Measurements of aerosol properties that were being carried out in the city during the resuspension episode indicate the presence of an enhanced concentration of aerosol particles in the boundary layer. Reports of ash on the runway at the airport near the measurement site correlate in time with the enhanced concentrations. Since the dynamics of ash resuspension and recirculation is similar to the dynamics of dust storms, we use the HYSPLIT model with the dust storm module to simulate the episode that affected Buenos Aires. The results of the modeling agree qualitatively with satellite lidar measurements.

scholarly journals OClO and BrO observations in the volcanic plume of Mt. Etna – implications on the chemistry of chlorine and bromine species in volcanic plumes

2015 ◽  
Vol 15 (10) ◽  
pp. 5659-5681 ◽  
Author(s):  
J. Gliß ◽  
N. Bobrowski ◽  
L. Vogel ◽  
D. Pöhler ◽  
U. Platt
Keyword(s):  
Heterogeneous Reaction ◽  
Early Morning ◽  
Optical Absorption Spectroscopy ◽  
Volcanic Plume ◽  
Plume Dispersion ◽  
Volcanic Plumes ◽  
Mixing Ratios ◽  
New Findings ◽  
Mt Etna ◽  
The Impact

Abstract. Spatial and temporal profiles of chlorine dioxide (OClO), bromine monoxide (BrO) and sulfur dioxide (SO2) of the volcanic plume at Mt. Etna, Italy, were investigated in September 2012 using Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS). OClO was detected in 119 individual measurements covering plume ages up to 6 min. BrO could be detected in 452 spectra up to 23 min downwind. The retrieved slant column densities (SCDs) reached maximum values of 2.0 × 1014 molecules cm-2 (OClO) and 1.1 × 1015 molecules cm-2 (BrO). Mean mixing ratios of BrO and OClO were estimated assuming a circular plume cross section. Furthermore, ClO mixing ratios were derived directly from the BrO and OClO-SCDs. Average abundances of BrO = 1.35 ppb, OClO = 300 ppt and ClO = 139 ppt were found in the young plume (plume age τ < 4 min) with peak values of 2.7 ppb (BrO), 600 ppt (OClO) and 235 ppt (ClO) respectively. The chemical evolution of BrO and OClO in the plume was investigated in great detail by analysing the OClO/SO2 and BrO/SO2 ratios as a function of plume age τ. A marked increase of both ratios was observed in the young plume (τ < 142 s) and a levelling off at larger plume ages showing mean SO2 ratios of 3.17 × 10-5 (OClO/SO2) and 1.65 × 10-4 (BrO/SO2). OClO was less abundant in the plume compared to BrO with a mean OClO/BrO ratio of 0.16 at plume ages exceeding 3 min. A measurement performed in the early morning at low solar radiances revealed BrO/SO2 and OClO/SO2 ratios increasing with time. This observation substantiates the importance of photochemistry regarding the formation of BrO and OClO in volcanic plumes. These findings support the current understanding of the underlying chemistry, namely, that BrO is formed in an autocatalytic, heterogeneous reaction mechanism (in literature often referred to as "bromine explosion") and that OClO is formed in the reaction of OClO with BrO. These new findings, especially the very detailed observation of the BrO and OClO formation in the young plume, were used to infer the prevailing Cl-atom concentrations in the plume. Relatively small values ranging from [Cl] = 2.5 × 106 cm-3 (assuming 80 ppb background O3) to [Cl] = 2.0 × 108 cm-3 (at 1 ppb O3) were calculated at plume ages of about 2 min. Based on these Cl abundances, a potential – chlorine-induced – depletion of tropospheric methane (CH4) in the plume was investigated. CH4 lifetimes between 14 h (at 1 ppb O3) and 47 days (at 80 ppb O3) were derived. While these lifetimes are considerably shorter than the atmospheric lifetime of CH4, the impact of gaseous chlorine on the CH4 budget in the plume environment should nevertheless be relatively small due to plume dispersion (decreasing Cl concentrations) and ongoing mixing of the plume with the surrounding atmosphere (replenishing O3 and CH4). In addition, all spectra were analysed for signatures of IO, OIO and BrO. None of these species could be detected. Upper limits for IO/SO2, OIO/SO2 and OBrO/SO2 are 1.8 × 10-6, 2.0 × 10-5 and 1.1 × 10-5 respectively.

Modelling aspects of the sulfate aerosol evolution after recent volcanic activity

2021 ◽  
Author(s):  
Christina Brodowsky ◽  
Timofei Sukhodolov ◽  
Aryeh Feinberg ◽  
Michael Höpfner ◽  
Thomas Peter ◽  
...  
Keyword(s):  
Volcanic Activity ◽  
Climate Model ◽  
Volcanic Eruptions ◽  
Stratospheric Aerosol ◽  
Sulfate Aerosol ◽  
Global Climate Models ◽  
Volcanic Plume ◽  
Free Running ◽  
Volcanic Emission ◽  
The Impact

&lt;p&gt;Volcanic activity is one of the main natural climate forcings and therefore an accurate representation of volcanic aerosols in global climate models is essential. However, direct modelling of sulfur chemistry, sulfate aerosol microphysics and transport is a complex task involving many uncertainties including those related to the volcanic emission magnitude, vertical shape of the plume, and observations of atmospheric sulfur. This study aims to investigate some of these uncertainties and to analyse the performance of the aerosol-chemistry-climate model SOCOL-AERv2 for three medium-sized volcanic eruptions from Kasatochi in 2008, Sarychev in 2009 and Nabro in 2011. In particular, we investigate the impact of different estimates for the initial volcanic plume height and its SO2 content on the stratospheric aerosol burden. The influence of internal model variability and of modelled dynamics is addressed by three free-running simulations and two nudged simulations at different vertical resolutions. Comparing the modelled evolution of the stratospheric aerosol loading and its spread with the Brewer-Dobson-Circulation (BDC) to satellite measurements reveals in general a very good performance of SOCOL-AERv2 during the considered period. However, the large spread in emission estimates logically leads to significant differences in the modelled aerosol burden. This spread results from both the uncertainty in the total emitted mass of sulfur as well as its vertical distribution relative to the tropopause. An additional source of modelled uncertainty is the tropopause height, which varies among the free-running simulations. Furthermore, the validation is complicated by disagreement between different observational datasets. Nudging effects on the tropospheric clouds were found to affect the tropospheric SO2 oxidation paths and the cross-tropopause transport, leading to increased background burdens both in the troposphere and the stratosphere. This effect can be reduced by nudging only horizontal winds but not temperature. A higher vertical resolution of 90 levels (as opposed to 39 in the standard version) increases the stratospheric residence time of sulfate aerosol after low-latitude eruptions by reducing the diffusion speed out of the tropical reservoir. We conclude that the model's uncertainties can be largely defined by both its set-up as by the volcanic emission parameters.&lt;/p&gt;

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