Variability and evolution of the midlatitude stratospheric aerosol budget from 22 years of ground-based lidar and satellite observations

Khaykin, Sergey; Godin‐Beekmann, Sophie; Keckhut, Philippe; Hauchecorne, Alain; Jumelet, Julien; Vernier, Jean‐Paul; Bourassa, A. E.; Degenstein, D. A.; Rieger, Landon; Bingen, Christine; Vanhellemont, F.; Robert, Charles; DeLand, Matthew T.; Bhartia, P. K.

doi:10.5194/acp-17-1829-2017

Cited by 72 publications

(95 citation statements)

References 67 publications

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“…A few Raman lidar studies were available (Ansmann et al, 1997;Mattis et al, 2010) that provided direct AEC and AOT measurements as well as measured extinction-to-backscatter ratios (lidar ratios). In Table 1, we used lidar ratios of 25 sr (Pinatubo) (Jäger and Deshler, 2003), 35 sr (moderate volcanic events) (Mattis et al, 2010), and 50 sr during quiet, non-volcanic times (Khaykin et al, 2017) to convert the 532 nm backscatter ratios and backscatter coefficients (derived from the standard backscatter lidar observation) to AEC and AOT values.…”

Section: Discussionmentioning

confidence: 99%

Extreme levels of Canadian wildfire smoke in the stratosphere over central Europe on 21–22 August 2017

et al. 2018

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Abstract. Light extinction coefficients of 500 Mm −1 , about 20 times higher than after the Pinatubo volcanic eruptions in 1991, were observed by European Aerosol Research Lidar Network (EARLINET) lidars in the stratosphere over central Europe on 21-22 August 2017. Pronounced smoke layers with a 1-2 km vertical extent were found 2-5 km above the local tropopause. Optically dense layers of Canadian wildfire smoke reached central Europe 10 days after their injection into the upper troposphere and lower stratosphere which was caused by rather strong pyrocumulonimbus activity over western Canada. The smoke-related aerosol optical thickness (AOT) identified by lidar was close to 1.0 at 532 nm over Leipzig during the noon hours on 22 August 2017. Smoke particles were found throughout the free troposphere (AOT of 0.3) and in the pronounced 2 km thick stratospheric smoke layer at an altitude of 14-16 km (AOT of 0.6). The lidar observations indicated peak mass concentrations of 70-100 µg m −3 in the stratosphere. In addition to the lidar profiles, we analyzed Moderate Resolution Imaging Spectroradiometer (MODIS) fire radiative power (FRP) over Canada, and the distribution of MODIS AOT and Ozone Monitoring Instrument (OMI) aerosol index across the North Atlantic. These instruments showed a similar pattern and a clear link between the western Canadian fires and the aerosol load over Europe. In this paper, we also present Aerosol Robotic Network (AERONET) sun photometer observations, compare photometer and lidar-derived AOT, and discuss an obvious bias (the smoke AOT is too low) in the photometer observations. Finally, we compare the strength of this recordbreaking smoke event (in terms of the particle extinction coefficient and AOT) with major and moderate volcanic events observed over the northern midlatitudes.

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Section: Discussionmentioning

confidence: 99%

Extreme levels of Canadian wildfire smoke in the stratosphere over central Europe on 21–22 August 2017

et al. 2018

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“…In this paper, we focus on a moderate volcanic eruption, the Sarychev eruption in 2009 (VEI = 4), which is considered as one of the high-latitude eruptions that affect tropical latitudes (von Savigny et al, 2015) and which is responsible for the increase in tropical stratospheric aerosol optical depth (Khaykin et al, 2017;Rieger et al, 2015). In particular, we study the transport pathway of the Sarychev SO 2 emission and sulfate aerosol from the extratropical lower stratosphere to the tropical tropopause layer (TTL).…”

Section: Introductionmentioning

confidence: 99%

Equatorward dispersion of a high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009

Grießbach²,

Hoffmann³

2017

Atmos. Chem. Phys.

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Abstract. Tropical volcanic eruptions have been widely studied for their significant contribution to stratospheric aerosol loading and global climate impacts, but the impact of high-latitude volcanic eruptions on the stratospheric aerosol layer is not clear and the pathway of transporting aerosol from high latitudes to the tropical stratosphere is not well understood. In this work, we focus on the high-latitude volcano Sarychev (48.1 • N, 153.2 • E), which erupted in June 2009, and the influence of the Asian summer monsoon (ASM) on the equatorward dispersion of the volcanic plume. First, the sulfur dioxide (SO 2 ) emission time series and plume height of the Sarychev eruption are estimated with SO 2 observations of the Atmospheric Infrared Sounder (AIRS) and a backward trajectory approach using the Lagrangian particle dispersion model Massive-Parallel Trajectory Calculations (MPTRAC). Then, the transport and dispersion of the plume are simulated using the derived SO 2 emission time series. The transport simulations are compared with SO 2 observations from AIRS and validated with aerosol observations from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The MPTRAC simulations show that about 4 % of the sulfur emissions were transported to the tropical stratosphere within 50 days after the beginning of the eruption, and the plume dispersed towards the tropical tropopause layer (TTL) through isentropic transport above the subtropical jet. The MPTRAC simulations and MIPAS aerosol data both show that between the potential temperature levels of 360 and 400 K, the equatorward transport was primarily driven by anticyclonic Rossby wave breaking enhanced by the ASM in boreal summer. The volcanic plume was entrained along the anticyclone flows and reached the TTL as it was transported southwestwards into the deep tropics downstream of the anticyclone. Further, the ASM anticyclone influenced the pathway of aerosols by isolating an "aerosol hole" inside of the ASM, which was surrounded by aerosol-rich air outside. This transport barrier was best indicated using the potential vorticity gradient approach. Long-term MIPAS aerosol detections show that after entering the TTL, aerosol from the Sarychev eruption remained in the tropical stratosphere for about 10 months and ascended slowly. The ascent speed agreed well with the ascent speed of the water vapor tape recorder. Furthermore, a hypothetical MPTRAC simulation for a wintertime eruption was carried out. It is shown that under winter atmospheric circulations, the equatorward transport of the plume would be suppressed by the strong subtropical jet and weak wave breaking events. In this hypothetical scenario, a high-latitude volcanic eruption would not be able to contribute to the tropical stratospheric aerosol layer.

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“…Discuss., https://doi.org /10.5194/acp-2017- Attenuation from molecules is computed based on modelling, but that by particles are generally not considered in studies based on CALIOP data. For example, Vernier et al (2009) and Khaykin et al (2017) discuss that the attenuation from particles is less than 1% at 15 km altitude in absence of strong volcanic eruptions, arguing that corrections are unnecessary during these time periods. Assuming 2 = 1, the expression for the SR corrected from molecular extinction becomes:…”

Section: Attenuation Of the Lasermentioning

confidence: 99%

“…The molecular part is estimated from modelling data of the molecular background (Winker et al, 2009;Young et al, 2005), while the influence of the other generally is considered negligible (e.g. 25 Khaykin et al, 2017;Vernier et al, 2009). We will discuss this in section 5, along with a method we developed to correct for the increased attenuation occurring during periods when volcanism increased the stratospheric aerosol load.…”

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confidence: 99%

Volcanic impact on the climate – the stratospheric aerosol load in the period 2006–2015

Friberg¹,

Martinsson²,

Andersson³

et al. 2018

Preprint

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Abstract. We present a study on the stratospheric aerosol load during 2006-2015, discuss the influence from volcanism and other sources, and reconstruct an AOD data-set in a resolution of 1° latitudinally and 8 days timewise. Our attempt is to include the "entire" stratosphere, from the tropopause to the almost particle free altitudes of the mid-stratosphere. A dynamic tropopause of 1.5 PVU was found to be the best suited one, enclosing almost all of the volcanic signals in the CALIOP dataset. New methods were developed to handle bias in the data. The data were successfully cleaned from polar stratospheric 10 clouds using a temperature threshold of 195 K. Furthermore, a method was developed to correct data when the CALIPSO laser beam was strongly attenuated by volcanic aerosol, preventing a negative bias in the AOD data-set. Tropospheric influence, likely from upwelling dust, was found in the extratropical transition layer in spring. Eruptions of both extratropical and tropical volcanoes that injected aerosol into the stratosphere impacted the stratospheric aerosol load for up to a year if their clouds reached lower than 20 km altitudes, whereas deeper reaching tropical injections rose in the tropical pipe and 15 impacted it for several years. Over the years 2006-2015, volcanic eruptions increased the stratospheric AOD on average by ~40%. In absolute numbers the stratospheric AOD and radiative forcing amounted to 0.008 and -0.2 Wm -2 , respectively.

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Variability and evolution of the midlatitude stratospheric aerosol budget from 22 years of ground-based lidar and satellite observations

Cited by 72 publications

References 67 publications

Extreme levels of Canadian wildfire smoke in the stratosphere over central Europe on 21–22 August 2017

Extreme levels of Canadian wildfire smoke in the stratosphere over central Europe on 21–22 August 2017

Equatorward dispersion of a high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009

Volcanic impact on the climate – the stratospheric aerosol load in the period 2006–2015

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