Impact of volcanic sulfate aerosols on the stratospheric heating: implications on the Quasi-Biennial Oscillation

Abstract. Large and moderate volcanic eruptions significantly impact Earth's atmosphere by releasing sulphur emissions, thereby affecting atmospheric dynamics and QBO. Using the ECHAM6-HAMMOZ model, we show the impact of eruptive volcanoes on the tropical stratosphere and Quasi-biennial oscillation (QBO) from 2001 to 2013. Our simulations with volcanoes, when compared without volcanoes, show that volcanic sulfate aerosols enhance the stratospheric aerosol optical depth (SAOD) two months after the eruption of Rabaul (0.0034); Sarychev (0.0040) and Nabro (0.0097). The enhanced SOAD in the tropics (0.0014) led to a radiative forcing at the top of the atmosphere (TOA) by -0.92±0.34 W m^-2 and at the surface by -0.88±0.18 W m^-2 in the tropical region. The volcanic aerosol precursors enter the tropical stratosphere, propagating upward and enhancing sulfate aerosol concentrations by 46.95 ng m⁻³ and heating rates by 0.13±0.05×10⁻² K d⁻¹. The QBO estimated from model simulations using the wavelet analysis shows that stratospheric heating caused by the volcanoes reduces the amplitude of the QBO and disrupts its phases, resulting in the prolongation of the easterly phase by ~12 to 20 months and the westerly phase by ~16 to 24 months. The secondary meridional circulation induced by the QBO produces the double-peak structure in the amplitude near the equator, with peaks at 10 hPa and at 50 hPa. Our study points out that moderate and large volcanoes modulate the QBO. Since QBO also modulates tropical convection and weather, we suggest including volcanic eruptions and the QBO in weather prediction models for a better forecast.