Eruption Research Articles

REVIEW: Story of Rabaul eruptions has lessons for wider Pacific

Return to Volcano Town: Reassessing the 1937-43 volcanic eruptions at Rabaul, by R. Wally Johnson and Neville Threlfall (editors). Canberra: ANU Press, 2023. 410 pages, ISBN 9781760466039. EARLY one morning in 1953 my father and kiap David Hook set out from Popondetta to climb Mount Lamington in what was then the Territory of Papua and New Guinea. Mount Lamington had exploded in January 1951, the largest eruption on January 21 releasing a pyroclastic flow that roared down the mountain and killed an estimated 3000 people. The carriers working with my father and the patrol officer abandoned them as the approached the mountain and it was towards the end of the day that my father came home, his boots cut to ribbons by the volcanic rock, his clothes ragged and soaked in sweat and his pockets full of colour slide film.

Coastal Hazards in the Sunda Strait: Mitigation Strategy and Coastal Management

Abstract Sunda strait is one of the strategic waters in Indonesia situated at the Indonesian archipelagic sea lane passage. The water is also known as one of the national strategic regions as governed in the Presidential Decree of 32/2019 about marine spatial planning. The coasts of the region have been developed as industrial areas, marine tourism and associated facilities, fisheries, agriculture, mining, etc. Despite the huge economic potency, Sunda Strait has high coastal hazards due to volcanic and tectonic activities. The Krakatau volcanic eruption in 1883 generated a tsunami run-up to ∼35 m high causing catastrophic damage along the coasts of Banten and Lampung and more than 36.000 people were reported killed. More recently, the eruption and flank collapse of the Anak Krakatau volcano generated a tsunami in the Sunda Strait causing severe damage, extensive inundation, and more than 430 deaths. Likewise, the Sunda Strait has a high potency of tsunami impacts generated by the earthquake sourced from the subduction zone known as megathrust. These conditions must become a valued lesson learned to all of us to raise awareness and preparedness through mitigation-based disaster management. Thus, we can reduce the impacts of the disaster and the high investment for post-disaster rehabilitation and reconstruction.

Quantifying the Impact of Internal Variability on the CESM2 Control Algorithm for Stratospheric Aerosol Injection

AbstractEarth system models are powerful tools to simulate the climate response to hypothetical climate intervention strategies, such as stratospheric aerosol injection (SAI). Recent simulations of SAI implement a tool from control theory, called a controller, to determine the quantity of aerosol to inject into the stratosphere to reach or maintain specified global temperature targets, such as limiting global warming to 1.5°C above pre‐industrial temperatures. This work explores how internal (unforced) climate variability can impact controller‐determined injection amounts using the Assessing Responses and Impacts of Solar climate intervention on the Earth system with Stratospheric Aerosol Injection (ARISE‐SAI) simulations. Since the ARISE‐SAI controller determines injection amounts by comparing global annual‐mean surface temperature to predetermined temperature targets, internal variability that impacts temperature can impact the total injection amount as well. Using an offline version of the ARISE‐SAI controller and data from Earth system model simulations, we quantify how internal climate variability and volcanic eruptions impact injection amounts. While idealized, this approach allows for the investigation of a large variety of climate states without additional simulations and can be used to attribute controller sensitivities to specific modes of internal variability.

Comment on “Stratospheric Aerosol Composition Observed by the Atmospheric Chemistry Experiment Following the 2019 Raikoke Eruption” by Boone et al.

AbstractBased on satellite observations in the Arctic stratosphere at latitudes from 61° to 66°N in the second half of 2019, Boone et al. (2022, https://doi.org/10.1029/2022jd036600) provide the impression that the aerosol in the upper troposphere and lower stratosphere (UTLS) over the entire Arctic consisted of sulfate aerosol originating from the Raikoke volcanic eruption in the summer of 2019. Here, we show that this was most probably not the case and the aerosol layering conditions were much more complex. By combining the stratospheric aerosol typing results of Boone et al. (2022, https://doi.org/10.1029/2022jd036600) with lidar observations at 85°–86°N of Ohneiser et al. (2021, https://doi.org/10.5194/acp‐21‐15783‐2021) of a dominating wildfire smoke layer in the UTLS height range, we demonstrate that the Arctic UTLS aerosol most likely consisted of Siberian wildfire smoke in the lower part and sulfate aerosol in the upper part of the aerosol layer which extended from 7 to 19 km height and was well observable until May 2020. The smoke‐ and sulfate‐related aerosol optical thickness (AOT) fractions were about 0.7–0.8 and 0.2–0.3, respectively, according to our analysis. The sulfate AOT is in good agreement with model‐based predictions of the Raikoke sulfate AOT.

Detection and Characterization of Seismic and Acoustic Signals at Pavlof Volcano, Alaska, Using Deep Learning

AbstractVolcanic tremor is a semi‐continuous seismic and/or acoustic signal that occurs at time scales ranging from seconds to years, with variable amplitudes and spectral features. Tremor sources have often been related to fluid movement and degassing processes, and are recognized as a potential geophysical precursor and co‐eruptive geophysical signal. Eruption forecasting and monitoring efforts need a fast, robust method to automatically detect, characterize, and catalog volcanic tremor. Here we develop VOlcano Infrasound and Seismic Spectrogram Network (VOISS‐Net), a pair of convolutional neural networks (one for seismic, one for acoustic) that can detect tremor in near real‐time and classify it according to its spectral signature. Specifically, we construct an extensive data set of labeled seismic and low‐frequency acoustic (infrasound) spectrograms from the 2021–2022 eruption of Pavlof Volcano, Alaska, and use it to train VOISS‐Net to differentiate between different tremor types, explosions, earthquakes and noise. We use VOISS‐Net to classify continuous data from past Pavlof Volcano eruptions (2007, 2013, 2014, 2016, and 2021–2022). VOISS‐Net achieves an 81.2% and 90.0% accuracy on the seismic and infrasound test sets respectively, and successfully characterizes tremor sequences for each eruption. By comparing the derived seismoacoustic timelines of each eruption with the corresponding eruption chronologies compiled by the Alaska Volcano Observatory, our model identifies changes in tremor regimes that coincide with observed volcanic activity. VOISS‐Net can aid tremor‐related monitoring and research by making consistent tremor catalogs more accessible.

Occurrence of Equatorial Plasma Bubbles (EPBs) Over the Indian Region on 15 January 2022 and Their Plausible Connection to the Tonga Volcano Eruption

AbstractThis study focuses on the causes for the generation of equatorial plasma bubbles (EPBs) over the Indian subcontinent and their correlation with atmospheric‐ionospheric disturbances resulting from the eruption of the Tonga volcano on 15 January 2022. Concurrent ionosonde observations obtained from Tirunelveli (8.67°N, 77.81°E) and Prayagraj (25.41°N, 81.93°E) show the presence of spread‐F traces in ionograms. Notably, the EPBs are also accompanied by plasma blobs (PBs), with their pronounced occurrence during midnight at Prayagraj and Tirunelveli. Analysis of in situ electron density observations obtained from the Swarm B and C satellites reveals substantial plasma density depletions associated with EPBs. An intriguing observation is the intensification of Pre‐Reversal Enhancement (PRE) immediately preceding the onset of spread‐F at Tirunelveli due to enhanced eastward F region zonal winds by Tonga Volcano, as seen in the satellite observations. Furthermore, the isofrequency analysis from Tirunelveli shows the presence of gravity wave‐like oscillations in the equatorial F‐region over India. The investigation of Total Electron Content (TEC) obtained from a Pseudo Random Number (PRN)‐14 over Indian longitudes suggests the presence of two dominant modes of Traveling Ionospheric Disturbances (TIDs) with speeds ∼452 m/s and ∼406 m/s having periods in the range of ∼65–75 min. These observations reaffirm that volcano triggered atmospheric/ionospheric disturbances can propagate long distances for several hours and can provide necessary seeding conditions for the generation of EPBs.

Evolving Particles in the 2022 Hunga Tonga—Hunga Ha'apai Volcano Eruption Plume

AbstractThe Multi‐angle Imaging SpectroRadiometer (MISR) aboard NASA's Terra satellite observed the Hunga Tonga—Hunga Ha'apai (HTHH) 15 January eruption plume on eight occasions between 15 and 23 January 2022. From the MISR multi‐angle, multi‐spectral imagery we retrieve aerosol plume height geometrically, along with plume‐level motion vectors, and derive radiometrically constraints on particle effective size, shape, and light‐absorption properties. Parts of two downwind aerosol layers were observed in different places and times, one concentrated in the upper troposphere (11–18 km ASL), and a mid‐stratosphere layer ∼23–30+ km ASL. After the initial day (1/15), the retrievals identified only spherical, non‐light‐absorbing particles, typical of volcanic sulfate/water particles. The near‐tropopause plume particles show constant, medium‐small (several tenths of a micron) effective size over 4 days. The mid‐stratosphere particles were consistently smaller, but retrieved effective particle size increased between 1/17 and 1/23, though they might have decreased slightly on 1/22. As a vast amount of water was also injected into the stratosphere by this eruption, models predicted relatively rapid sulfate particle growth from the modest amounts of SO2 gas injected by the eruption to high altitudes along with the water (Zhu et al., 2022, https://doi.org/10.5194/acp‐22‐10267‐2022). MISR observations up to 10 days after the eruption are consistent with these model predictions. The possible decrease in stratospheric particle size after initial growth was likely caused by evaporation, as the plume mixed with drier, ambient air. Particles in the lower‐elevation plume observed on 1/15 were larger than all the downwind aerosols and contained significant non‐spherical (likely ash) particles.

Model of Surface Subsidence of Pyroclastic Flow: the August 29, 2019 Shiveluch Volcano Eruption, Kamchatka

Model of Surface Subsidence of Pyroclastic Flow: the August 29, 2019 Shiveluch Volcano Eruption, Kamchatka

The Andean Southern Volcanic Zone: a review on the legacy of the latest volcanic eruptions

The Andean Southern Volcanic Zone (SVZ) concentrates many of the most active volcanoes of the Andean continental arc, as well as the region’s most recent and impactful volcanic eruptions. In this contribution, we briefly revise the general characteristics of the SVZ volcanism and provide a synthesis of the scientific findings related to the latest volcanic eruptions (430 peer-reviewed publications with over 9,000 citations, with large-magnitude (VEI 4-5) eruptions being the most studied. Our study shows that SVZ research has been primarily focused on environmental and atmospheric impacts (29%), eruption descriptions and physical volcanology (20%), volcanic hazard and risk assessments (15%), and other investigations complementary to volcanology. Whereas the least silicic eruptions (e.g., Llaima 2008-2009 and Villarrica 2015) shed light on magma replenishment and degassing dynamics controlling eruption styles, intermediate eruptions (andesitic-dacitic) offered clues on either rapid or slow eruption initiation, with relevant findings on phreatic-to-magmatic style transitions and eruption triggering mechanisms. On the other hand, silicic (i.e., rhyolite-rhyodacite) eruptions provided unique observations on rapid magma ascent, high-rate magma extrusion, rheology, fragmentation processes, and style transitions. These recent eruptions have also inspired a new generation of tephrochronological, tephrostratigraphical, and physical volcanology studies, aimed at assessing the long-term (kyr-scale) evolution of the volcanic systems and their associated hazards. We debate how the knowledge gained from research and the long-term human coexistence with volcanoes are relevant to reducing volcanic risk in the SVZ. Finally, we discuss how challenges and opportunities emerging from other disciplines can complement our understanding of volcanism in this active region.

Toward Resilience City: Potential Hazards and Scenario for Ternate Island, North Maluku

Natural hazards and climate change significantly threaten almost every small island. This is due to the small island's isolation and lack of resources. Ternate Island is a small island that is now afflicted by this issue. Geographically, the island is surrounded by active plates and volcanic paths, making it at risk of serious catastrophes. Population growth and limited land resources also contribute to a high disaster susceptibility. We characterize the features of the small island of Ternate by classifying the types of disasters that threaten it based on a literature database. Earthquakes, volcanic eruptions, floods, extreme weather events, and tsunamis are natural disasters that occur often in Ternate. Additionally, these findings indicate the significant importance of a multi-hazard approach to disaster response. Our examination concludes with some recommendations for establishing the resilience of Ternate City.

Five Large 13th Century C.E. Volcanic Eruptions Recorded in Antarctica Ice Cores

Five Large 13th Century C.E. Volcanic Eruptions Recorded in Antarctica Ice Cores

Volcanic activity during the Early–Middle Triassic transition in the Sichuan Basin, South China: Duration, evolution and implications

The felsic volcanogenic tuff known as ‘green bean rock’ (GBR) and its carbonates are widely dispersed across the western Yangtze Block. This study investigates the origin, tectonic setting and genesis of GBR, as well as the environmental disruptions evident in carbonates from the western edge of the Yangtze Block. The analyses include mineralogy, whole‐rock geochemistry and the isotopic composition of zircon Hf, carbon and oxygen in GBR samples from the western edge of the Yangtze Block. The geochemical profile of GBR shows enriched LREE, Th and U content, depleted levels of Nb, Ta, Sr, Ba, K, Rb and Ti, and strong‐to‐moderate negative Eu anomalies (δEu = 0.15–0.18). Zircon Hf isotopes exhibit S‐type geochemical affinities with low negative εHf(t) values (−13.3 to −5.7) and TDM2 ages of 1684–2110 Ma. This suggests that the volcanic ashes originate from the magma of an intermediate to felsic composition. X‐ray directionality data show that the most prevalent clay minerals are illite and illite/smectite. Lithium fixed in these minerals is likely to have leached from brine. Early Triassic variances in δ13C profiles are reliable indicators of environmental disturbances, pointing to cycles of devastation and restoration in marine ecosystems, interspersed with extraneous events including volcanic activity. The study posits that volcano eruptions may have prolonged biotic recovery after the end‐Permian mass extinction.

Airfall volume of the 15 January 2022 eruption of Hunga volcano estimated from ocean color changes

On 15 January 2022, Hunga volcano erupted, creating an extensive and high-reaching umbrella cloud over the open ocean, hindering traditional isopach mapping and fallout volume estimation. In MODIS satellite imagery, ocean surface water was discolored around Hunga following the eruption, which we attribute to ash fallout from the umbrella cloud. By relating intensity of ocean discoloration to fall deposit thicknesses in the Kingdom of Tonga, we develop a methodology for estimating airfall volume over the open ocean. Ash thickness measurements from 41 locations are used to fit a linear relationship between ash thickness and ocean reflectance. This produces a minimum airfall volume estimate of 1.8-0.4+0.3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${1.8}_{-0.4}^{+0.3}$$\\end{document} km3. The whole eruption produced > 6.3 km3 of uncompacted pyroclastic material on the seafloor and a caldera volume change of 6 km3 DRE. Our fall estimates are consistent with the interpretation that most of the seafloor deposits were emplaced by gravity currents rather than fall deposits. Our proposed method does not account for the largest grain sizes, so is thus a minimum estimate. However, this new ocean-discoloration method provides an airfall volume estimate consistent with other independent measures of the plume and is thus effective for rapidly estimating fallout volumes in future volcanic eruptions over oceans.

Eruption Forecasting Model for Copahue Volcano (Southern Andes) Using Seismic Data and Machine Learning: A Joint Interpretation with Geodetic Data (GNSS and InSAR)

Abstract Anticipating volcanic eruptions remains a challenge despite significant scientific advancements, leading to substantial human and economic losses. Traditional approaches, like volcano alert levels, provide current volcanic states but do not always include eruption forecasts. Machine learning (ML) emerges as a promising tool for eruption forecasting, offering data-driven insights. We propose an ML pipeline using volcano-seismic data, integrating precursor extraction, classification modeling, and decision-making for eruption alerts. Testing on six Copahue volcano eruptions demonstrates our model’s ability to identify precursors and issue advanced warnings pseudoprospectively. Our model provides alerts 5–75 hr before eruptions and achieving a high true negative rate, indicating robust discriminatory power. Integrating short- and long-term data reveals seismic sensitivity, emphasizing the need for comprehensive volcanic monitoring. Our approach showcases ML’s potential to enhance eruption forecasting and risk mitigation. In addition, we analyze long-term geodetic data (Interferometric Synthetic Aperture Radar and Global Navigation Satellite System) to assess Copahue volcano deformation trends, in which we notice an absence of noteworthy deformation in the signals associated with the six small eruptions, aligning with their small magnitude.

Initial atmospheric conditions control transport of volcanic volatiles, forcing and impacts

Abstract. Volcanic eruptions impact the climate and environment. The volcanic forcing is determined by eruption source parameters, including the mass and composition of volcanic volatiles, eruption season, eruption latitude, and injection altitude. Moreover, initial atmospheric conditions of the climate system play an important role in shaping the volcanic forcing and response. However, our understanding of the combination of these factors, the distinctions between tropical and extratropical volcanic eruptions, and the co-injection of sulfur and halogens remains limited. Here, we perform ensemble simulations of volcanic eruptions at 15 and 64° N in January, injecting 17 Mt of SO2 together with HCl and HBr at 24 km altitude. Our findings reveal that initial atmospheric conditions control the transport of volcanic volatiles from the first month and modulate the subsequent latitudinal distribution of sulfate aerosols and halogens. This results in different volcanic forcing, surface temperature and ozone responses over the globe and Northern Hemisphere extratropics (NHET) among the model ensemble members with different initial atmospheric conditions. NH extratropical eruptions exhibit a larger NHET mean volcanic forcing, surface cooling and ozone depletion compared with tropical eruptions. However, tropical eruptions lead to more prolonged impacts compared with NH extratropical eruptions, both globally and in the NHET. The sensitivity of volcanic forcing to varying eruption source parameters and model dependency is discussed, emphasizing the need for future multi-model studies to consider the influence of initial conditions and eruption source parameters on volcanic forcing and subsequent impacts.

The impact of the Hunga Tonga–Hunga Ha’apai volcanic eruption on the Peruvian atmosphere: from the sea surface to the ionosphere

The eruption of the Hunga Tonga Hunga Ha’apai volcano on 15 January 2022 significantly impacted the lower and upper atmosphere globally. Using multi-instrument observations, we described disturbances from the sea surface to the ionosphere associated with atmospheric waves generated by the volcanic eruption. Perturbations were detected in atmospheric pressure, horizontal magnetic field, equatorial electrojet (EEJ), ionospheric plasma drifts, total electron content (TEC), mesospheric and lower thermospheric (MLT) neutral winds, and ionospheric virtual height measured at low magnetic latitudes in the western South American sector (mainly in Peru). The eastward Lamb wave propagation was observed at the Jicamarca Radio Observatory on the day of the eruption at 13:50 UT and on its way back from the antipodal point (westward) on the next day at 07:05 UT. Perturbations in the horizontal component of the magnetic field (indicative of EEJ variations) were detected between 12:00 and 22:00 UT. During the same period, GNSS-TEC measurements of traveling ionospheric disturbances (TIDs) coincided approximately with the arrival time of Lamb and tsunami waves. On the other hand, a large westward variation of MLT winds occurred near 18:00 UT over Peru. However, MLT perturbations due to possible westward waves from the antipode have not been identified. In addition, daytime vertical plasma drifts showed an unusual downward behavior between 12:00 and 16:00 UT, followed by an upward enhancement between 16:00 and 19:00 UT. Untypical daytime eastward zonal plasma drifts were observed when westward drifts were expected. Variations in the EEJ are highly correlated with perturbations in the vertical plasma drift exhibiting a counter-equatorial electrojet (CEEJ) between 12:00 and 16:00 UT. These observations of plasma drifts and EEJ are, so far, the only ground-based radar measurements of these parameters in the western South American region after the eruption. We attributed the ion drift and EEJ perturbations to large-scale thermospheric wind variations produced by the eruption, which altered the dynamo electric field in the Hall and Pedersen regions. These types of multiple and simultaneous observations can contribute to advancing our understanding of the ionospheric processes associated with natural hazard events and the interaction with lower atmospheric layers.Graphical

A Lie symmetry approach to traveling wave solutions, bifurcation, chaos and sensitivity analysis of the geophysical Korteweg–de Vries equation

Strong waves known as tsunamis are caused by earthquakes, landslides, or volcanic eruptions that traverse oceans. This article examines the geophysical Korteweg–de Vries (GPKdV) equation, which controls the propagation of tsunami waves in seas. The study involves exploring symmetry diminution exerted Lie group analysis, examining the properties of the dynamical structure with the help of bifurcation phase pictures, and researching the dynamic demeanor of the perturbed dynamical system utilizing chaos theory. Techniques such as 3D and 2D phase portraits, time series analysis, poincaré maps, looking into the existence of multistability in the autonomous structure under diverse beginning circumstances, lyapunov exponent, and bifurcation diagram are applied to identify chaotic demeanor. Furthermore, the study establishes general forms of solitary wave results, containing periodic, trigonometric, and singular soliton results, by using the unified Riccati equation expansion approach to address the examined problem analytically. These results are visually represented as 2D and 3D graphs with cautiously chosen parameters, along with their accompanying constraint conditions. Moreover, the sensitivity evaluation of the investigated equation is discussed and demonstrated pictorially. The discoveries revealed are intriguing, novel, and potentially helpful in understanding a wide range of physical events in engineering and science.

Using paintings to teach about the impact of environmental hazards

ABSTRACT Paintings depicting elements of the natural environment can be an effective educational tool, useful for teachers at every educational stage. The article discusses the use of figurative painting in teaching about environmental hazards. For this purpose, eight paintings were selected, each depicting a different environmental hazard impact – hurricane, flood, earthquake and volcano eruption. Each painting was then examined for its content and depicted elements. Based on the research, it can be concluded that paintings depicting environmental hazards are an important source of knowledge in geographical studies, and can teach about various processes and their effects in space. The introduction of the use of paintings in the educational process can help understand and appreciate art, and also demonstrate that it can be an educational tool in geography or other empirical sciences.

Capturing Extraordinary Multisensory Experiences in Writing: Reports on Natural Disasters in an 18th Century Newspaper Corpus

The article examines reports of natural disasters in the 18th century Austrian newspaper "Wienerisches Diarium" to gain insights into how people captured the extraordinary sensory experiences of such events in written form. By analysing a digitised corpus of over 300 newspaper issues, the study identifies 302 text passages referring to natural disasters, among them 285 news reports, and explores textual traces of (multi)sensuality present within this material. The close reading and semantic annotation of the textual findings reveals that comparisons to familiar sensations are commonly used to convey the sensory experiences of natural disasters, allowing readers to (better) relate to and understand the extreme events. At the same time, touch and vision constitute the most frequently mentioned senses, while smell and taste only play a minor role in early modern disaster depiction. In addition, the study finds that earthquakes and volcanic eruptions are more likely to include multisensory descriptions compared to other types of disasters. These and further findings shed light on when and how (multi)sensory impressions of disasters were conveyed in written form within early modern news.

The Recovery and Re-Calibration of a 13-Month Aerosol Extinction Profiles Dataset from Searchlight Observations from New Mexico, after the 1963 Agung Eruption

The recovery and re-calibration of a dataset of vertical aerosol extinction profiles of the 1963/64 stratospheric aerosol layer measured by a searchlight at 32° N in New Mexico, US, is reported. The recovered dataset consists of 105 aerosol extinction profiles at 550 nm that cover the period from December 1963 to December 1964. It is a unique record of the portion of the aerosol cloud from the March 1963 Agung volcanic eruption that was transported into the Northern Hemisphere subtropics. The data-recovery methodology involved re-digitizing the 105 original aerosol extinction profiles from individual Figures within a research report, followed by the re-calibration. It involves inverting the original equation used to compute the aerosol extinction profile to retrieve the corresponding normalized detector response profile. The re-calibration of the original aerosol extinction profiles used Rayleigh extinction profiles calculated from local soundings. Rayleigh and aerosol slant transmission corrections are applied using the MODTRAN code in transmission mode. Also, a best-estimate aerosol phase function was calculated from observations and applied to the entire column. The tropospheric aerosol phase function from an AERONET station in the vicinity of the searchlight location was applied between 2.76 to 11.7 km. The stratospheric phase function, applied for a 12.2 to 35.2 km altitude range, is calculated from particle-size distributions measured by a high-altitude aircraft in the vicinity of the searchlight in early 1964. The original error estimate was updated considering unaccounted errors. Both the re-calibrated aerosol extinction profiles and the re-calibrated stratospheric aerosol optical depth magnitudes showed higher magnitudes than the original aerosol extinction profiles and the original stratospheric aerosol optical depth, respectively. However, the magnitudes of the re-calibrated variables show a reasonable agreement with other contemporary observations. The re-calibrated stratospheric aerosol optical depth demonstrated its consistency with the tropics-to-pole decreasing trend, associated with the major volcanic eruption stratospheric aerosol pattern when compared to the time-coincident stratospheric aerosol optical depth lidar observations at Lexington at 42° N.