Size-Resolved Stratospheric Aerosol Distributions after Pinatubo Derived from a Coupled Aerosol-Chemistry-Climate Model
Size-Resolved Stratospheric Aerosol Distributions after Pinatubo Derived from a Coupled Aerosol-Chemistry-Climate Model
Thursday, 22 March 2018
Iriarte (Hotel Botanico)
Abstract:
We employ the coupled aerosol-chemistry-climate model SOCOL-AER to investigate the interactions between stratospheric aerosol loading, aerosol microphysical processes, radiative effects, and responses in atmospheric chemistry and dynamics after the 1991 eruption of Mt. Pinatubo. The aerosol module includes comprehensive sulfur chemistry and microphysics, in which the particle size distribution is represented by 40 size bins spanning radii from 0.39 nm
to 3.2 μm. Radiative forcing is calculated online using the aerosol optical properties calculated according to Mie theory. The simulations are compared with the satellite and in situ measurements of different aerosol parameters. An accurate sedimentation scheme is found to be essential to prevent particles diffusing too rapidly to high and low altitudes. The aerosol radiative feedback and the use of a nudged quasibiennial oscillation (QBO) help to sustain the aerosol in the tropical reservoir and significantly affect the evolution of stratospheric aerosol burden, improving the agreement with observed mass distributions. Large uncertainty among observations, however, doesn’t allow us to conclude the necessity of a sophisticated particle coagulation scheme and to determine an exact sufficient initial emission rate for Pinatubo, which differs largely among similar models. A main issue found for SOCOL-AER model is some overestimation of the post-eruption lower stratospheric warming in late 1991. Besides this, our results show that SOCOL-AER is already a sufficient tool for an accurate prediction of atmospheric and climate effects following large volcanic eruptions, which is also a prerequisite for improved understanding of anthropogenic effects.
to 3.2 μm. Radiative forcing is calculated online using the aerosol optical properties calculated according to Mie theory. The simulations are compared with the satellite and in situ measurements of different aerosol parameters. An accurate sedimentation scheme is found to be essential to prevent particles diffusing too rapidly to high and low altitudes. The aerosol radiative feedback and the use of a nudged quasibiennial oscillation (QBO) help to sustain the aerosol in the tropical reservoir and significantly affect the evolution of stratospheric aerosol burden, improving the agreement with observed mass distributions. Large uncertainty among observations, however, doesn’t allow us to conclude the necessity of a sophisticated particle coagulation scheme and to determine an exact sufficient initial emission rate for Pinatubo, which differs largely among similar models. A main issue found for SOCOL-AER model is some overestimation of the post-eruption lower stratospheric warming in late 1991. Besides this, our results show that SOCOL-AER is already a sufficient tool for an accurate prediction of atmospheric and climate effects following large volcanic eruptions, which is also a prerequisite for improved understanding of anthropogenic effects.