The influence of the asian summer monsoon on volcanic aerosol transport in the utls region

ABSTRACT This study analyses the influence of the Asian summer monsoon on volcanic aerosol transport. Realistic, altitude-resolved SO2 emissions of a middle-latitude volcanic eruption

(Sarychev 2009) and a tropical volcanic eruption (Nabro 2011) were retrieved and used to initialize the simulations of the long-range transport and dispersion of the sulfate aerosol plumes.

The barrier effect of the Asian summer monsoon anticyclone (ASMA) isolated the Sarychev eruption plume outside of the ASMA but constrained the Nabro eruption plume inside of the ASMA, which

is most evident in the UTLS region between isotropic surfaces of 360–420 K. Meanwhile, the ASMA could transport a fraction of the plume outside of ASMA quasi-horizontally to the tropical

tropopause layer along the southeastern periphery of the anticyclonic circulation, and lift the volcanic plume inside the ASMA anticyclonically across the tropopause with an ascent rate of

approximately 0.8 K/day. By enhancing the meridional transport in the UTLS region and lifting volcanic aerosols across the tropopause, the ASMA significantly expanded the potential effects

of volcanic eruptions. SIMILAR CONTENT BEING VIEWED BY OTHERS VOLCANIC FORCING OF HIGH-LATITUDE NORTHERN HEMISPHERE ERUPTIONS Article Open access 08 January 2024 CLIMATE CHANGE MODULATES THE

STRATOSPHERIC VOLCANIC SULFATE AEROSOL LIFECYCLE AND RADIATIVE FORCING FROM TROPICAL ERUPTIONS Article Open access 12 August 2021 LONG RANGE TRANSPORT OF SOUTH AND EAST ASIAN ANTHROPOGENIC

AEROSOLS COUNTERACTING ARCTIC WARMING Article Open access 13 May 2024 INTRODUCTION The regional and global climate impacts of volcanic aerosols in the upper troposphere/lower stratosphere

(UTLS) have received great attention. Although there have been few large volcanic eruptions in recent decades, small and medium volcanic eruptions have continuously increased stratospheric

aerosol levels. The sulfate aerosol from volcanism has become a significant source of aerosols in the tropical UTLS1,2. For instance, recent small and medium-sized volcanic eruptions, such

as Kasatochi (2008), Sarychev (2009), and Raikoke (2019) in the extratropics and Nabro (2011) and Ulawun (2019) in the tropics, have enhanced stratospheric aerosol loading3,4,5,6,7 and have

had a profound impact on the global aerosol optical depth of the stratosphere8. Other studies suggest that nonvolcanic aerosol particles, e.g., anthropogenic sulfur, black carbon, and

organic carbon released at the Earth’s surface, may also be a relevant source of the stratospheric aerosol layer9,10. In that case, it is essential to accurately estimate the climate impacts

of volcanic eruptions because the climate impact of anthropogenic greenhouse gases and aerosol particles could be better assessed if natural forcings, such as volcanic eruptions, are

explicit. The atmospheric background conditions, the amount of emitted SO2, and the plume heights of volcanic eruptions are all essential parameters that directly determine the transport

pathways of volcanic SO2 and sulfate aerosols. Tropical volcanic eruptions may inject SO2 and sulfate aerosols directly into the tropical tropopause layer (TTL). From the TTL, those sulfur

emissions are transported upward by the ascending branch of the Brewer–Dobson circulation and then spread to the middle and high-latitude stratosphere. Although the sulfur emissions from

volcanic eruptions in the middle and high latitudes may not directly enter the Brewer–Dobson circulation, they may take advantage of the extratropical Rossby wave breaking to transport

sulfur from the extratropical UTLS to the TTL. The Asian summer monsoon (ASM) is one of the essential transport mechanisms between the extratropical UTLS and the TTL in boreal

summer11,12,13. The ASM is featured with a strong anticyclonic circulation in the UTLS, the Asian summer monsoon anticyclone (ASMA), ranging from East Asia to the Middle East14. The ASMA can

significantly increase transport between low and middle latitudes in the UTLS region. The persistent deep convection associated with the ASM may transport trace gases and aerosols from the

atmospheric boundary layer upward into the UTLS15,16,17,18,19,20. However, although the role of the ASM in atmospheric constituent transport and exchange is gradually recognized, the

influence of the ASM on aerosol transport is still under investigation21,22. One critical reason is that the limited spatial and temporal resolution of existing volcanic SO2 observations and

inventories fails to properly constrain realistic volcanic aerosol transport and dispersion. In this study, we investigate the role of the ASM in transporting volcanic plumes in the UTLS

region. High-resolution sulfur emissions retrieved for the two volcanic eruptions, the Sarychev eruption in June 2009 and the Nabro eruption in June 2011, are used as “realistic” tracers for

transport studies. The Sarychev volcano (48.1°N and 153.2°E) is located northeast of the ASM. In contrast, the Nabro volcano (13.4°N and 41.7°E) is on the southwest edge of the ASM. These

two volcanic eruptions distinguished by geographical locations and time are typical cases for investigating the influence of the ASM on volcanic aerosol transport between the tropics and

extratropics inside and outside of the ASM. RESULTS VOLCANIC SO2 EMISSION TIME SERIES The time series of the altitude-resolved SO2 injections from the Sarychev and Nabro eruptions are shown

in Fig. 1. The Sarychev eruption started on 12 June 2009. The eruption continued for ~5 days, and the SO2 injections varied in height and magnitude. The most significant SO2 injections were

on 14–15 June between 10–18 km, and minor emissions followed until 16 June. Approximately 58% of the SO2 (0.8 Tg) was injected into the lower stratosphere. For the Nabro eruption, the peak

emissions were on 12 June 2011, 12 UTC to 13 June 2011, and 06 UTC at 14–18 km. Additional emissions occurred since 14 June 2011 and the peak emissions were at 7 and 11 km. In the first 2

days (12–13 June), most of the SO2 (~55%) was injected directly into the lower stratosphere. About 26% of SO2 (0.95 Tg) was injected into the lower stratosphere during the whole eruption

period. The timelines of the two eruptions generally agree with the Global Volcanism Program reports23,24, and the temporal development and plume heights of the two eruptions are consistent

with more detailed studies25,26,27,28 too. The volcanic SO2 emission estimations with high altitude and temporal resolutions were used to initialize forward transport simulations. Based on

the reconstructed SO2 emissions, we assigned 100,000 air parcels for the Sarychev and Nabro eruption each. The total masses of SO2 for the two cases were 1.4 Tg and 3.65 Tg, respectively.

The SO2 mass in each air parcel was uniform, but the number of air parcels at a specific time and altitude was proportional to the SO2 emission rate at that time and altitude, as shown in

Fig. 1. Then, the ERA-Interim wind field was used to drive the forward transport and dispersion simulations of the volcanic plumes. Forward trajectories were calculated with the MPTRAC model

from the volcanos’ first eruption to 31 July 2009, 00 UTC for the Sarychev case, and 31 July 2011, 00 UTC for the Narbo case. During the trajectory simulations, the depletion of SO2 was

also simulated with hydroxyl chemistry, i.e., the chemical decomposition of SO2 by hydroxyl radicals. We assumed that the sulfate aerosol converted from SO2 remained in the volcanic plume in

the UTLS region. The simulation outputs are given every three hours. For conciseness, the evolutions of the volcanic SO2 and the transport of the aerosol particles are evaluated by

comparing with satellite observations in the Supplementary information. THE HORIZONTAL BARRIER EFFECT OF THE ASMA Figure 2 shows cross-sections of the ASMA in the boreal summers of 2009 and

2011. The ASMA is among the most prominent circulation patterns during summer in the Northern Hemisphere UTLS. It features an area of strongly negative potential vorticity (PV) anomalies

because of its anticyclonic upper-level circulation, ranging approximately between the isentropic surfaces of 360–420 K, and it is also subject to dynamical variabilities29. The northern

part of the ASMA is bounded by subtropical westerlies. Moreover, the tropopause over the ASMA region is relatively higher than the zonal mean tropopause. With the long-range transport

simulations, it is straightforward to see the ASMA circulation’s influence on the volcanic plume’s transport pathway. Figure 3 shows the distributions and evolution of the volcanic plume of

the Sarychev eruption in the altitude range of the ASMA. The black contour is the geopotential height of 14,320 m on the pressure level of 150 hPa, which is commonly used as the boundary of

the ASMA15. The color shading denotes the percentage of volcanic plume parcels in each 2° × 1° bin to the total air parcels during the period of consideration. After the eruption, the

volcanic plume generally dispersed eastward from 12 to 30 June 2009 and remained at middle and high latitudes (Fig. 3a). After another ten days (by 10 July 2009), a fraction of air parcels

was dragged into the anticyclonic circulation of the ASMA transported toward the tropical UTLS, i.e., TTL (Fig. 3b). Later, more air parcels were entrained along the southern and eastern

flank of the ASMA and spread toward the tropics (Fig. 3c, d). The barrier effect of the ASMA was more prominent as a hole of aerosol was formed after 10 July. The transport of the Nabro

eruption plume further demonstrated the barrier effect of the ASMA. As the Nabro volcano was located at the southwest edge of the ASMA in 2011, the volcanic plume was immediately wrapped

into the anticyclone after the eruption and transported to higher latitudes in the Northern Hemisphere (Fig. 4a). Similar to previous studies29,30,31,32, one important mechanism for air

parcels escaping from the AMSA is the eastward-migrating anticyclones breaking off from the main anticyclone and the filaments separated on the northeastern and southwestern flanks of the

anticyclone (Fig. 4b–d). The 14,320 m geopotential height contour over North America indicates the North American monsoon (NAM). The NAM occurs due to a similar mechanism as the ASM, i.e.,

the differences in thermal properties between land and ocean. The NAM plays a similar role as the ASM in Fig. 3, transporting aerosols from middle latitudes to lower latitudes and isolating

aerosols outside of the anticyclonic circulation, but it is much weaker in strength. The ASM anticyclonic circulation generally promotes meridional transport as the subtropical jet retreats

northward in boreal summer. The clear difference between the plume transport of the two volcanic eruptions is mainly due to the barrier effect of the ASMA, which is particularly obvious in

the UTLS region. VERTICAL TRANSPORT OF VOLCANIC PLUMES IN THE CONVECTION REGION To further investigate the volcanic plume transport pathway within the ASMA, we analyzed the forward

trajectories of the Nabro eruption plume. The selected trajectories started from the SO2 emissions in the upper troposphere between 12 and 16 June 2011 and ended at the lower stratosphere

over the ASMA on 30 July 2011, as shown in Fig. 5. Figure 5a, b demonstrate the forward trajectories of five air parcels, colored by days since the starting date of the Nabro eruption to the

end of the trajectory simulation and the potential temperature, respectively. Figure 5c, d demonstrate the corresponding vertical cross-sections. The forward trajectories reflected the

anticyclonic circulation of the ASMA. In the first 15 days, the volcanic plume circulated the ASMA along isentropic surfaces quasi-horizontally in the low and middle latitudes. The

isentropic surfaces are tilted in the UTLS region, so the altitude of the plume vibrated between higher and lower altitude levels when circulating the ASMA. Afterward, while circulating

anticyclonically, the plume slowly elevated across the tropopause due to diabatic heating, forming large-scale spiral trajectories over the ASMA. Figure 5e, f demonstrate the statistics of

the potential temperature and altitude evolution of the trajectories. The potential temperature of the plume increased monotonously in the UTLS region, indicating that the diabatic heating

rate in the ASMA was positive, and the altitude of the plume started to increase monotonously after the first 15 days. Based on the median values, the increase rate of the potential

temperature, which is also the diabatic heating rate, was ~0.8 K per day. This slow upward transport in the ASMA has also been addressed in previous studies31,33. Thus, volcanic gases and

aerosols in the upper troposphere in the ASMA can be further elevated to the stratosphere over the ASMA. Moreover, as shown in ref. 34, the air masses at the top of the ASMA will be further

transported to the tropical stratosphere quasi-horizontally and enter the tropical pipe. Therefore, the ASMA plays a significant role in lifting volcanic plumes and expanding the influence

of volcanic eruptions. For the Sarychev eruption, the volcanic plume of the Sarychev eruption was mostly isolated outside of the ASM region, so the transport was not influenced by the

diabatic heating. Most of the Sarychev volcanic plumes that were injected into the mid-latitude lower stratosphere and were transported quasi-horizontally to the TTL by ASMA circulation (as

seen in Fig. 3) will undergo diabatic ascent due to the radiative heating there35. This vertical transport is not directly related to the ASM region but is significantly facilitated by ASMA

circulation. As to the SO2 emissions injected into the troposphere, we examined the transport process and found that only a small fraction of the volcanic plume that started right below the

mid-latitude tropopause could end in the tropical stratosphere. The vertical transport was also forced by the radiative heating in the TTL, which is not directly associated with the ASM

region either. More details are in the Supplementary information. DISCUSSION In this study, we retrieved the SO2 emissions from the Sarychev eruption (2009) and Nabro eruption (2011) and

investigated the transport of the volcanic plume in a realistic scenario under the influence of the ASM. Conventionally, a tropical volcanic eruption, such as the Nabro eruption, receives

more attention because it could inject SO2 and sulfate aerosol directly into the tropical UTLS, where the upward branch of the Brewer–Dobson circulation spreads the aerosol over the globe

and causes long-term climate effects. In contrast, an extratropical volcanic eruption, such as the Sarychev eruption, is usually thought to only have limited regional impacts because the SO2

and sulfate aerosol injected into the extratropical UTLS would encounter the downward branch of the Brewer–Dobson circulation and be eliminated from the stratosphere. As demonstrated above,

even though most of the volcanic aerosols from the Sarychev eruption remained in the middle and high latitudes, a small but significant part of the aerosols was transported

quasi-horizontally to the tropical UTLS by the ASMA. This meridional aerosol transport significantly enhanced the aerosol loading in the tropical stratosphere (also found in ref. 12). In

these scenarios, the volcanic aerosol from a middle-latitude volcanic eruption could enter the Brewer–Dobson circulation and spread to the stratosphere of both hemispheres. In this case, it

may impact global atmospheric radiation, similar to a tropical volcanic eruption. However, as a transport barrier, the ASMA generally prevented volcanic aerosols from entering the

anticyclone, resulting in an aerosol hole over the ASMA in the UTLS region. The boundary of the ASMA was initially defined by Randel and Park15 using the GPH of 14,320 m on the 150 hPa

pressure level that roughly represents the streamline near the maximum wind speed in the upper troposphere, corresponding to an area featuring steep trace gases gradients (high tropospheric

trace gases, e.g., CO and H2O, and low stratospheric trace gases, e.g., O3). As to the transport barrier effect of the ASMA, a PV-based boundary is more physically reasonable32. In the

layered two-dimensional PV-conserving flows, the displacement of PV isolines is smaller in a strong PV-gradient background than in a weak PV background due to pseudomomentum conservation36.

The smaller displacement of PV isolines means less Rossby wave breaking and hence less transport, so regions of enhanced PV gradients indicate the transport barriers37. The ASMA region is

characterized by negative and anomalously low PV and enhanced PV gradients at its boundary, so this PV-gradient barrier initially applied to the transport barrier of the polar vortex38,39,40

can also explain the barrier effect associated with the ASMA. In addition, the ASMA is bounded by the subtropical westerlies in the north and the tropical easterlies in the south (see Fig.

2). These zonal jets may inhibit meridional transport by increasing the intrinsic phase speed of Rossby waves, thereby suppressing Rossby wave breaking. This mechanism has been proved with

model experiments37,41, and the meridional transport barrier effect is verified to be true even for the subtropical jet in the boreal summer. So these zonal jets may contribute to the

barrier effect in the north and south of the ASMA, respectively, independent of the PV gradients. The barrier effect caused by the summer subtropical jets can also be explained by the

effective diffusivity mixing diagnostics42. For the Nabro eruption (2011), the ASMA transported most volcanic aerosol from the tropics to the middle latitudes. The aerosol was first confined

in the ASMA in the UTLS region and then slowly leaked toward the northeast and southwest. Bourassa et al.4 argued that the Nabro eruption (2011) injected volcanic gases below the

tropopause, and only via the ASM could the volcanic gases and aerosols ascend to the stratosphere, which raised broad discussions and some disagreements27,28. Our study found that during the

major eruption period (12–13 June 2011), the Nabro eruption injected part of the volcanic gases and aerosols directly into the lower stratosphere without the help of the ASM. Our study also

found the volcanic plume injected into the upper troposphere was lifted in anticyclonic upward spirals, and during the troposphere-to-stratosphere ascent, the potential temperature level

increased by ~0.8 K per day. With the isentropic surface of 360 K at 15.5 km and 420 K at 18.5 km35, an uplift of 1 km means an increase of potential temperature by about 20 K. The ascent

ratio of 0.8 K from this study results in an uplift of 1 km (20 K) in about 25 days due to radiative heating, which generally agrees with the radiative heating value previously deduced from

observations7 and model simulations31. But Bourassa et al.4 showed an uplift of 40 K in 12 days (from 380 K on 13 June 2011 to 420 K on 25 June 2011). The ascent ratio of 40 K in 12 days is

far beyond being explainable by radiative heating. The SO2 and sulfate aerosols injected into the troposphere were elevated to the stratosphere over the ASMA, from which they may further

migrate to the tropical pipe. In this case, an altitude-resolved SO2 emission inventory is necessary to accurately simulate the ASMA’s influence on plume transport. In summary, based on the

transport study of volcanic plumes under the influence of the ASM, we found that ASMA can significantly increase the meridional transport between the tropical and extratropical UTLS. At the

same time, the ASMA modulates the horizontal distribution of volcanic gases and aerosols due to its barrier effect. The ASMA also plays a significant role in troposphere-to-stratosphere

vertical transport, which may increase the stratospheric loading of volcanic aerosols and expand the potential impacts of volcanic eruptions. METHOD REANALYSIS DATA AND SATELLITE

MEASUREMENTS ERA5 is the fifth generation of reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF)43. We retrieved the hourly and monthly averaged data with

horizontal grids of 0.25° × 0.25° and the heights covering from 1000 to 1 hPa at 37 pressure levels to calculate the daily and monthly average of the range of the ASMA and calculate

diagnostic parameters, such as potential temperature, potential vorticity, and tropopause. ERA-Interim reanalysis data44 is also provided by the ECMWF. Data on 1° × 1° horizontal grids from

the surface to 0.1 hPa at 60 model levels were retrieved to drive the Lagrangian particle dispersion model. The ERA-Interim data are available 6-h at 00, 06, 12, and 18 UTC. Atmospheric

infrared sounder (AIRS) observations of SO2 are used to initialize and evaluate the Lagrangian transport simulations. AIRS is an infrared sounder on the Aqua satellite launched in May 200245

and orbits in a nearly polar, sun-synchronous orbit at an altitude of ~710 km and a period of 98 min. Each across-track scan covers a ground distance of 1780 km and has 90 footprints. The

footprint size varies between 13.5 km × 13.5 km at the nadir and 21.4 km × 41 km at the scan extremes. AIRS provides 14.5 orbits per day, covering the Earth approximately twice a day.

Volcanic eruptions of SO2 are detected from AIRS measurements using the brightness temperature (BT) difference method. The SO2 index (SI) is defined as the BT difference in the 7.3 µm

waveband: $${{{\mathrm{SI}}}} = {{{\mathrm{BT}}}}\left( {1412.87\;{{{\mathrm{cm}}}}^{ - 1}} \right) - {{{\mathrm{BT}}}}\left( {1371.52\;{{{\mathrm{cm}}}}^{ - 1}} \right)$$ This definition

improves the SI over the previous definition12,46 through a better choice of background channel (selecting 1412.87 cm−1 rather than 1407.2 cm−1). Moreover, this new SI is more sensitive to

low concentrations and performs better in suppressing background interfering noise. The AIRS SI is most sensitive to SO2 at altitudes in the UTLS region (8–13 km) and increases with

increasing SO2 column density. In this study, 4 K was set as the threshold, i.e., SI values greater than the threshold were identified as volcanic SO2 emissions. MPTRAC MODEL The transport

and dispersion of volcanic plumes are simulated with the Massive-Parallel Trajectory Calculations model (MPTRAC) Version 2.2. MPTRAC is a Lagrangian particle dispersion model (LPDM) suitable

for analyzing transport processes in the troposphere and stratosphere47,48. It uses wind fields from reanalyzed data to calculate the trajectories of particles by solving the kinematic

equation of motion. Additionally, the model includes subgrid-scale wind fluctuations and turbulent diffusion modules. Subgrid-scale wind fluctuations were simulated using the Langevin

equation. The turbulent diffusion is described by a fixed diffusion coefficient. In this study, a constant horizontal diffusion coefficient of 50 m2 s−1 was set for the troposphere, and a

vertical diffusion coefficient of 0.1 m2 s−1 was set for the stratosphere. The MPTRAC Version 2.2 added modules to simulate the effects of convection, sedimentation, dry deposition, wet

deposition, and hydroxyl chemistry on the depletion of SO2 and aerosols47. MPTRAC Version 2.2 significantly improved the simulations of the evolution of SO2 and sulfate aerosols and produced

more physically and chemically reasonable results compared with its older versions12,48. The MPTRAC model has been used in several studies to simulate the long-range transport of volcanic

SO2 and sulfate aerosols12,49,50. In this study, the MPTRAC model was driven with the ERA-Interim wind field, which gives the optimized balance between computational costs and accuracy48,51.

METHOD OF RECONSTRUCTING VOLCANIC SO2 EMISSION TIME SERIES The SO2 emissions from the two volcanic eruptions, Sarychev (2009) and Nabro (2011), and the subsequently converted sulfate

aerosols were used as “realistic” tracers to investigate the influence of the ASM on transporting the erupted materials. The method of reconstructing the time series of the mass and plume

height of the injected SO2 follows the basic ideas of ref. 48, which uses AIRS SO2 measurements and backward trajectories. Because AIRS only provides column density measurements without

altitude-resolved information, we set up a column at each location of the AIRS SO2 measurements (SO2 index). The altitude range of the column was 0–30 km, which may cover the vertical

dispersion range of the SO2 plume during the eruption period. A total number of 100,000 air parcels was assigned to all the columns, and the number of air parcels in each column was weighted

according to the SO2 index, and the vertical distribution of the air parcels in each column followed the mean kernel function of the AIRS SO2 measurements. The AIRS footprint size is

between 13.5 and 41 km, so in the horizontal plane, we chose 30 km as the full width at half maximum (FWHM) for the horizontal Gaussian scatter of the air parcels. Then, backward

trajectories were calculated for all air parcels. SO2 trajectories that were at least one day and up to 7 days and had passed the volcano domain were considered SO2 emissions of the volcanic

eruptions. The volcano domain was within a radius of 75 km from the volcanoes and a vertical range of 0–25 km, covering the injection height. These preassigned parameters were selected with

sensitivity experiments to optimize to obtain the best simulation results. This approach retrieves the realistic spatial and temporal distributions of SO2 emissions but requires the total

mass of SO2 from additional datasets48. Following estimations from previous studies52,53,54,55 and the Global Volcanism Program reports23,24, a total SO2 mass of 1.4 Tg and 3.65 Tg was

assigned to the Sarychev and Nabro eruptions, respectively. This approach was successfully used in reverse modeling of volcanic SO2 emissions of multiple volcanic eruptions12,33,48,49,50.

DATA AVAILABILITY The SO2 index data used in this study are available for download at https://datapub.fz-juelich.de/slcs/airs/volcanoes/ (last access: 30 June 2022). The MIPAS aerosol index

data used in this study are available for download at https://datapub.fz-juelich.de/slcs/mipas/aerosol_clouds/ (last access: 21 July 2022). The ERA-Interim reanalysis data were obtained from

the European Centre for Medium-Range Weather Forecasts (ECMWF). The ERA5 reanalysis data were retrieved from ECMWF Meteorological Archival and Retrieval System

(https://doi.org/10.24381/cds.adbb2d47 last accessed: 15 June 2022). CODE AVAILABILITY The code of the Massive-Parallel Trajectory Calculations (MPTRAC) model is available under the terms

and conditions of the GNU General Public License, Version 3 from the repository at https://github.com/slcs-jsc/mptrac (last access: 25 August 2021). The codes developed to analyze the data

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references ACKNOWLEDGEMENTS This study is supported by the National Natural Science Foundation of China (Grants 41975049, 42175046, 42065009, 41861134034, and 41905042). X Wu is also

supported by the Basic Strengthening Research Program (Grant 2021-JCJQ-JJ-1058), and the Ground-based Space Environment Comprehensive Monitoring Network (the Chinese Meridian Project II). B

Chen is supported by the Natural Science Foundation of Yunnan Province (Grant 201901BB050045). X Wang is supported by the Strategic Priority Research Program of the Chinese Academy of

Sciences (Grant XDA15021000). L Hoffmann is supported by the joint research project AeroTrac of the Deutsche Forschungsgemeinschaft (Grant DFG HO5102/1-1). YF Tian is supported by the Open

Research Project of Large Research Infrastructures of CAS-“Study on the interaction between low/mid-latitude atmosphere and ionosphere based on the Chinese Meridian Project”. YN Wang is

supported by the second Tibetan Plateau Scientific Expedition and Research Program (Grant 2019QZKK0604). AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Key Laboratory of Middle Atmosphere and

Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China Xue Wu, Xin Wang, Yufang Tian & Yinan Wang * University of Chinese Academy

of Sciences, Beijing, China Xue Wu, Xin Wang, Yufang Tian & Yinan Wang * Key Laboratory of Atmospheric Environment and Processes in the Boundary Layer over the Low‑Latitude Plateau

Region, Department of Atmospheric Science, Yunnan University, Kunming, China Qi Qiao & Bing Chen * Jülich Supercomputing Centre, Forschungszentrum Jülich, Jülich, Germany Lars Hoffmann 

& Sabine Griessbach Authors * Xue Wu View author publications You can also search for this author inPubMed Google Scholar * Qi Qiao View author publications You can also search for this

author inPubMed Google Scholar * Bing Chen View author publications You can also search for this author inPubMed Google Scholar * Xin Wang View author publications You can also search for

this author inPubMed Google Scholar * Lars Hoffmann View author publications You can also search for this author inPubMed Google Scholar * Sabine Griessbach View author publications You can

also search for this author inPubMed Google Scholar * Yufang Tian View author publications You can also search for this author inPubMed Google Scholar * Yinan Wang View author publications

You can also search for this author inPubMed Google Scholar CONTRIBUTIONS X. Wu and X. Wang developed the idea. All the authors discussed the concepts. X. Wu, Q.Q., and B.C. performed most

of the analysis. X. Wu drafted the manuscript and all authors edited and revised the manuscript. All authors approved the completed version of the manuscript. CORRESPONDING AUTHORS

Correspondence to Bing Chen or Xin Wang. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing interests. ADDITIONAL INFORMATION PUBLISHER’S NOTE Springer Nature remains

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influence of the Asian summer monsoon on volcanic aerosol transport in the UTLS region. _npj Clim Atmos Sci_ 6, 11 (2023). https://doi.org/10.1038/s41612-023-00339-w Download citation *

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