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

Abstract

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.

A New Volcanic Stratospheric Sulfate Aerosol Forcing Emulator (EVA_H): Comparison With Interactive Stratospheric Aerosol Models

“…Red dashed line shows predictions from EVA_H with a fixed 25 km injection height. (c) Global mean SAOD time series (525 nm) from observations (GloSSAC and ; Friberg et al, ) and EVA_H using the volcanic SO emission databases used in the Interactive Stratospheric Aerosol Model Intercomparison Project (ISA‐MIP, Timmreck et al, ): Bingen et al () (VolcDB1, 1997–2012), Neely and Schmidt () (VolcDB2, 1990–2014), Carn et al () (VolcDB3, 1979–2015), and the subset of the strongest eight eruptions over 1998–2012 with parameters (SO mass and height) averaged from all other databases used in Timmreck et al ().…”

Formation and composition of the UTLS aerosol

“…8b, 380-470 K). 17 These aerosol clouds reached approximately the same altitude in the same season, when the extratropical downward transport in the Brewer-Dobson circulation is weak. 40 The wildfire shows decline already within the first two weeks.…”

“…In this period the conditions in the LMS varied due to influence from volcanism. 8,17 To avoid effects of strong variability in the data set, only periods of relatively weak volcanic impact were used. 10 Data from that month was not used either.…”

“…16 In approximately the same period as studied here, several volcanic eruptions increased the global stratospheric aerosol optical depth (AOD) by on average 40%. 17 The stratospheric aerosol contains a large fraction of sulfuric acid and water, a carbonaceous fraction and some minor components of extraterrestrial or tropospheric origin. [18][19][20][21] The carbonaceous aerosol is mainly organic 10 with a small fraction of black carbon.…”

Long-term (1999–2019) variability of stratospheric aerosol over Mauna Loa, Hawaii, as seen by two co-located lidars and satellite measurements

“…The extinction profiles required for this correction are derived from the closest pressure and temperature profiles available from MERRA-2. While the effect of the aerosol extinction could also be included in the calculation or corrected using an iterative approach (Friberg et al, 2018), its contribution is small for the cases presented in this study and compared to other uncertainty sources.…”