Stratospheric aerosol layer perturbation caused by the 2019 Raikoke and Ulawun eruptions and their radiative forcing

Abstract

Abstract. In June 2019 a stratospheric eruption occurred at Raikoke (48∘ N, 153∘ E). Satellite observations show the injection of ash and SO2 into the lower stratosphere and an early entrainment of the plume into a cyclone. Following the Raikoke eruption, stratospheric aerosol optical depth (sAOD) values increased in the whole Northern Hemisphere and tropics and remained enhanced for more than 1 year, with peak values at 0.040 (short-wavelength, high northern latitudes) to 0.025 (short-wavelength, Northern Hemisphere average). Discrepancies between observations and global model simulations indicate that ash may have influenced the extent and evolution of the sAOD. Top of the atmosphere radiative forcings are estimated at values between −0.3 and -0.4Wm-2 (clear-sky) and of −0.1 to -0.2Wm-2 (all-sky), comparable to what was estimated for the Sarychev eruption in 2009. Almost simultaneously two significantly smaller stratospheric eruptions occurred at Ulawun (5∘ S, 151∘ E) in June and August. Aerosol enhancements from the Ulawun eruptions mainly had an impact on the tropics and Southern Hemisphere. The Ulawun plume circled the Earth within 1 month in the tropics. Peak shorter-wavelength sAOD values at 0.01 are found in the tropics following the Ulawun eruptions and a radiative forcing not exceeding −0.15 (clear-sky) and −0.05 (all-sky). Compared to the Canadian fires (2017), Ambae eruption (2018), Ulawun (2019) and the Australian fires (2019/2020), the highest sAOD and radiative forcing values are found for the Raikoke eruption.

Measurement Report: Lidar measurements of stratospheric aerosol following the 2019 Raikoke and Ulawun volcanic eruptions

“…For moderate-magnitude eruptions, Mattis et al (2010) 2010) quoted 63 ± 10 sr for the Kasatochi plume of 2008. Remarkably consistent though these results are, Mie scattering calculations suggest that the lidar ratio depends strongly on particle size as well as composition (Korshunov and Zubachev, 2013) and therefore varies from eruption to eruption.…”

Near‐Global Variability of Stratospheric Water Vapor Observed by SAGE III/ISS

“…Overall, these comparisons demonstrate that SAGE III/ISS sampling and data quality are adequate for monitoring stratospheric water vapor variability and changes. The SAGE III/ISS water vapor retrievals show higher sensitivity to enhanced stratospheric aerosol loadings during the events of volcanic eruptions (Chouza et al., 2020; Kloss et al., 2021) and wildfires (Kablick et al., 2020). We have applied stricter filtering criteria to remove the outliers and caution is needed in filtering the data in these extreme events (see, Davis et al., 2021 for details).…”

Tracking aerosols and SO<sub>2</sub> clouds from the Raikoke eruption: 3D view from satellite observations

“…Figure 7 also shows that the effects of the eruption lasted for almost a year. Increased aerosol loading in the lower stratosphere can also be attributed to two pyroCumulonimbus (pyroCb) events that took place before and after the eruption, Alberta fires (June 18) and Siberian fires (July 2) (Kloss et al, 2021 between 20˚N and 90˚N shows the vertical transport of the Raikoke plume to higher altitudes and its persistence in the lower stratosphere (Fig. 8).…”