The global climate system is sensitive to changes in the content of the atmosphere. The injection of sulfur into the stratosphere by volcanic eruptions is a major natural driver of climate variability. Due to reduction in the incoming radiation due to aerosol scattering, the tropospheric temperature decreases. This effect can last for several years, depending on the strength of the eruption. Undoubtedly, changes in net radiation and tropospheric temperature also affect the dynamics of the lower atmosphere. Particularly, the changes in the Hadley cell and the jet streams also take place. Atmosphere-ocean general circulation model simulations, which include radiative forcing associated with the 1815 Tambora eruption and 1991 Pinatubo eruption, were used to investigate the impact of volcanic aerosol on tropospheric thermodynamics and large-scale atmospheric circulation. A special emphasis was placed on the Hadley circulation. Hadley cell changes were assessed for both boreal (December — February) and austral (June — August) winters. The spatial anomalies of the Hadley circulation are similar in magnitude and structure to published analysis of simulations that include stratospheric aerosol forcing from artificial sulfate atmospheric injection. The Carnot cycle method was used to estimate the power generated by the Hadley circulation. In these simulations, the power generated by the Hadley cells decreased by 0.5%--2.0% in the first two years after the Pinatubo eruption and 2.0% — 8.0% in the first two years after the Tambora eruption. The Carnot cycle approach shows expected decreases in the power of the Hadley circulation for the boreal and austral winters. The Northern Hemisphere jet stream anomalies in boreal winter were investigated. The slowdown of the jet stream is 0.2% — 4.5% in the first two years after the Pinatubo eruption and 2.0% — 12.5% in the first two years after the Tambora eruption. The jet stream also shows an expected decrease in zonal wind speed and wavy patterns. The relationship between the wave activity in midlatitudes and the Hadley cell edge is not obvious and varies among different models. This effect can last for two years, depending on the strength of the eruption. Prior studies have investigated changes in atmospheric dynamics caused by anthropogenic changes. This work shows that the same methods can be successfully used to estimate tropospheric changes caused by strong volcanic eruptions.
Anton Poroshenko (Wed,) studied this question.