Long-term variation of stratospheric aerosols observed with lidars over Tsukuba, Japan, from 1982 and Lauder, New Zealand, from 1992 to 2015

Abstract

Vertical distributions of stratospheric aerosols have been measured with lidars over Tsukuba, Japan, since 1982 and Lauder, New Zealand, since 1992 to study the long‐term and seasonal variations and influences of climate change. After volcanic eruptions of El Chichón in 1982 and Mount Pinatubo in 1991, the vertically integrated stratospheric aerosol backscattering coefficient (IBC) increased to over 30 times the minimum level over the two sites. The IBC increased to more than twice the minimum over Tsukuba after volcanic eruptions in the northern high latitudes (Okmok, Kasatochi, and Sarychev) and tropics (Nabro) between 2000 and 2011. Over Lauder, the IBC increased to more than twice the minimum after volcanic eruptions in the southern high latitudes (Puyehue‐Cordón Caulle and Calbuco) and tropics (Kelud) between 2011 and 2015. The IBC showed seasonal variations with higher values in winter than in summer over the two sites. The mean radiative forcing by the stratospheric aerosols during the period 2000–2015 is estimated to be −0.15 ± 0.07 and −0.13 ± 0.06 W m−2 over the two sites, which partially canceled the increase of global mean radiative forcing by CO2.

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

“…For example, the sensitivity of the stratospheric mean β aero to the assumed lidar ratio was estimated to be ∼ 0.15 % sr −1 under background aerosol conditions (September 2005) and ∼ 0.23 % sr −1 under volcanically perturbed conditions (September 2011). Our estimates are compatible with those provided by Sakai et al (2016). It should be noted that the error in the lidar ratio has a larger effect on aerosol extinction and optical depth, whose uncertainty may thus be somewhat larger.…”

“…Between mid-1997 and late 2001 aerosol loading remains stable, with no discernible eruption-induced enhancements at Northern Hemisphere (NH) midlatitudes. This is fully consistent with other midlatitude lidar observations (Deshler et al, 2006;Trickl et al, 2013;Sakai et al, 2016). Although some VEI 4 eruptions between 2000 and 2003 have occurred over that time, they had very limited stratospheric impact (Vernier et al, 2011a;Kremser et al, 2016).…”

“…By September 2015 the Kelud plume is no longer observed at OHP: the value in September 2015 is not much different from the preKelud observations in 2013 and 2014, which suggests that the trend estimate is unaffected by the Kelud plume. Lidar observations at Tsukuba, 36 • N (Sakai et al, 2016) do not show any indication of the presence of the Kelud plume in 2015.…”

“…Similarly, the extinction-to-backscatter (lidar) ratio is set to 50 sr after 1997, which is a commonly assumed value for volcanically quiescent conditions and periods of moderate eruptions (e.g., Trickl et al, 2013;Ridley et al, 2014;Sakai et al, 2016). The molecular backscatter is calculated from the National Centers for Environmental Prediction (NCEP) daily meteorological data interpolated to the OHP location.…”

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

“…However, there is no doubt that major volcanic eruptions have by far the largest impact on weather and climate. After the Pinatubo eruption, the sulfuric-acid aerosol was distributed over both hemispheres (Sakai et al, 2016) and the 500 nm AOT at northern mid latitudes was > 0.1 for more than 2 years. Particles were present from the tropopause to a height of about 25 km for several years.…”