The Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP)

Abstract:

The Stratospheric Sulfur and its Role in Climate (SSiRC) interactive stratospheric aerosol model intercomparison project (ISA-MIP) explores uncertainties in the processes that connect volcanic emission of sulphur gas species and the radiative forcing associated with the resulting enhancement of sulphuric acid. The central aim of ISA-MIP is to constrain and improve interactive stratospheric aerosol models and reduce uncertainties in the radiative forcing of stratospheric aerosols through the comparison of results of standardized model experiments with a range of observations. The experiments have been designed to investigate key processes which influence the formation and temporal development of stratospheric aerosol in different time periods of the observational record. The “Background” (BG) experiment will focus on microphysics and transport processes under volcanically quiescent conditions, when the stratospheric aerosol is controlled by the transport of aerosols and their precursors from the troposphere to the stratosphere. The “Transient Aerosol Record” (TAR) experiment will explore the role of small- to moderate-magnitude volcanic eruptions, anthropogenic sulphur emissions and transport processes over the period 1998-2012 and their role in the warming hiatus. Two further experiments will investigate the stratospheric sulphate aerosol evolution after large volcanic eruptions. The “Historical Eruptions SO2 Emission Assessment” (HErSEA) experiment will focus on the uncertainty in the initial emission of recent large-magnitude volcanic eruptions, while the “Pinatubo Emulation in Multiple models” (PoEMS) experiment will provide a detailed uncertainty analysis of the radiative forcing of the 1991 Mt. Pinatubo eruption. Here we will introduce the experiment and present first results.