Abstract
Abstract. Explosive volcanic eruptions influence near-surface temperature and precipitation especially in the monsoon regions, but the impact varies with different eruption seasons and latitudes. To study this variability, two groups of ensemble simulations are performed with volcanic eruptions in June and December at 0∘ representing an equatorial eruption (EQ) and at 30∘ N and 30∘ S representing Northern and Southern Hemisphere eruptions (NH and SH). Results show significant cooling especially in areas with enhanced volcanic aerosol content. Compared to the EQ eruption, stronger cooling emerges in the Northern Hemisphere after the NH eruption and in the Southern Hemisphere after the SH eruption. Stronger precipitation variations occur in the tropics than in the high latitudes. Summer and winter eruptions lead to similar hydrological impacts. The NH and the SH eruptions have reversed climate impacts, especially in the regions of the South Asian summer monsoon (SASM). After the NH eruption, direct radiative effects of volcanic aerosols induce changes in the interhemispheric and land–sea thermal contrasts, which move the intertropical convergence zone (ITCZ) southward and weaken the SASM. This reduces the moisture transport from the ocean and reduces cloud formation and precipitation in India. The subsequent radiative feedbacks due to regional cloud cover lead to warming in India. After the SH eruption, vice versa, a northward movement of the ITCZ and strengthening of the SASM, along with enhanced cloud formation, lead to enhanced precipitation and cooling in India. This emphasizes the sensitivity of regional climate impacts of volcanic eruptions to eruption latitude, which relates to the dynamical response of the climate system to radiative effects of volcanic aerosols and the subsequent regional physical feedbacks. Our results indicate the importance of considering dynamical and physical feedbacks to understand the mechanism behind regional climate responses to volcanic eruptions and may also shed light on the climate impact and potential mechanisms of stratospheric aerosol engineering.
Highlights
Sulfate aerosols in the stratosphere from explosive volcanic eruptions significantly cool the surface by reflecting incoming solar radiation (Robock, 2000; Timmreck, 2012)
For the EQ eruption cases, the AOD550 indicates that volcanic aerosols are transported to both hemispheres, associated with a stronger dispersion than in the NH and SH cases, and more aerosols are transported to the Northern Hemisphere in the winter case and to the Southern Hemisphere in the summer case
This indicates that the transport of volcanic aerosols from equatorial eruptions to high latitudes depends on the eruption season, which is related to the large-scale transport of the Brewer–Dobson circulation (Hamill et al, 1997)
Summary
Sulfate aerosols in the stratosphere from explosive volcanic eruptions significantly cool the surface by reflecting incoming solar radiation (Robock, 2000; Timmreck, 2012). This further affects the Earth’s hydrological cycle. Inverse effects of interhemispherically asymmetric volcanic aerosols were found in Sahelian precipitation (Haywood et al, 2013; Jacobson et al, 2020), monsoon climates (Iles and Hegerl, 2014; Liu et al, 2016; Zhuo et al, 2014) and tropical hydroclimates in general (Colose et al, 2016; Zuo et al, 2018).
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