Abstract
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 (SO2) emission time series and plume height of the Sarychev eruption are estimated with SO2 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 SO2 emission time series. The transport simulations are compared with SO2 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.
Highlights
The impact of volcanic aerosol on climate has received widespread attention over decades. Robock (2000, 2013) gave a comprehensive review on this subject
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 and which is responsible for the increase in tropical stratospheric aerosol optical depth (Khaykin et al, 2017; Rieger et al, 2015)
In the first 19 days (Fig. 8a), from the first eruption on 12 to 30 June 2009, the plume mostly moved eastward and remained at mid- and high latitudes. After another 10 days (Fig. 8b), air parcels were entrained into the anticyclonic circulation of the American monsoon and a fraction was shed towards the tropics
Summary
The impact of volcanic aerosol on climate has received widespread attention over decades. Robock (2000, 2013) gave a comprehensive review on this subject. The sulfate aerosol is responsible for profound effects on the global climate (McCormick et al, 1995; Robock, 2000). Several studies focused on small and moderate-sized volcanic eruptions (VEI ≤ 4; Kravitz et al, 2011; Solomon et al, 2011; Vernier et al, 2011; Ridley et al, 2014) and considered them as the primary source of the notable increase in stratospheric aerosol since 2000 that slowed down global warming (Solomon et al, 2011; Neely et al, 2013; Haywood et al, 2014). We study the transport pathway of the Sarychev SO2 emission and sulfate aerosol from the extratropical lower stratosphere to the tropical tropopause layer (TTL).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
