Major influence of tropical volcanic eruptions on the stratospheric aerosol layer during the last decade

Abstract

International audienceThe variability of stratospheric aerosol loading between 1985 and 2010 is explored with measurements from SAGE II, CALIPSO, GOMOS/ENVISAT, and OSIRIS/Odin space-based instruments. We find that, following the 1991 eruption of Mount Pinatubo, stratospheric aerosol levels increased by as much as two orders of magnitude and only reached "background levels" between 1998 and 2002. From 2002 onwards, a systematic increase has been reported by a number of investigators. Recently, the trend, based on ground-based lidar measurements, has been tentatively attributed to an increase of SO2 entering the stratosphere associated with coal burning in Southeast Asia. However, we demonstrate with these satellite measurements that the observed trend is mainly driven by a series of moderate but increasingly intense volcanic eruptions primarily at tropical latitudes. These events injected sulfur directly to altitudes between 18 and 20 km. The resulting aerosol particles are slowly lofted into the middle stratosphere by the Brewer-Dobson circulation and are eventually transported to higher latitudes

Composition and evolution of volcanic aerosol from eruptions of Kasatochi, Sarychev and Eyjafjallajökull in 2008–2010 based on CARIBIC observations

“…Not only massive eruptions such as those mentioned above are of importance to the stratospheric aerosol load. A study by Vernier et al (2011) based on satellite observations shows that eruptions of lower explosivity are also an important source of stratospheric aerosol. Their effect is visible in the increase of the stratospheric aerosol layer that has occurred since 2002 after a period with little volcanic influence.…”

Towards a combined SAGE II and SCIAMACHY aerosol dataset and implications for stratospheric aerosol trend analysis over East Asia

“…Recent observational studies on stratospheric aerosols show that, on the global scale, stratospheric aerosol loading has increased by 4%-10% per year since 2000 (Hofmann et al 2009;Nagai et al 2010;Vernier et al 2011). These studies have shown that stratospheric aerosol loading is significantly influenced by atmospheric dynamics, human industrial emissions, and moderate volcanic eruptions.…”

“…These studies have shown that stratospheric aerosol loading is significantly influenced by atmospheric dynamics, human industrial emissions, and moderate volcanic eruptions. Several studies have proposed that the increase in anthropogenic sulfur emissions is the main source of the observed increasing trend in stratospheric aerosol loading (Hofmann et al 2009); however, other studies have demonstrated that small and medium strength volcanic eruptions could be the primary source of the observed increases in stratospheric aerosol (Vernier et al 2011;Neely III et al 2013;Brühl et al 2015). The main reasons behind the increase remain the subject of ongoing research.…”

The Aerosol Limb Imager: acousto-optic imaging of limb-scattered sunlight for stratospheric aerosol profiling

“…However, the stratospheric backscatter signal is weak and requires averaging of only the nighttime measurements over several days and typically 0.5 km vertically and 500 km horizontally (Vernier et al, 2011b). Additionally, the uncertainty in the calibration with respect to the molecular background that is on the order of the stratospheric aerosol signal leads to a potential bias in the stratospheric measurements (Rogers et al, 2011).…”

“…However, the global distribution, which can only really be obtained with satellite observations, provides invaluable insight into aerosol processes and variability. A good example of this is the use of satellite observations by Vernier et al (2011b) to determine that the increased stratospheric aerosol load reported by Hofmann et al (2009) was in fact due to a series of relatively minor, mostly tropical, volcanic eruptions.…”