A key component of the CLDERA project is generating simulation data for use in tracing simulated pathways from the eruption source to its impacts, demonstrating robust attribution of impacts and systematically evaluating uncertainty.
Under CLDERA, we have modified version 2 of the Energy Exascale Earth System Model (E3SM v2) to include prognostic volcanic aerosols that simulate the chemical and microphysical evolution of the volcanically erupted sulfur-dioxide gas into sulfate aerosols in the stratosphere. This implementation has been validated by comparing simulated aerosols from the Mt. Pinatubo eruption with benchmark simulations from the Whole Atmosphere Community Climate Model version 6 (WACCM6) and observations as described in the pre-print “Validating a microphysical prognostic stratospheric aerosol implementation in E3SMv2 using the Mount Pinatubo eruption."
To provide initial conditions for simulations of Mt. Pinatubo and to confirm that the prognostic aerosol implementation did not modify the equilibrium climate state, we completed a 100-year pre-industrial control run and two 165-year historical simulations. We then generated 10 ensembles initialized from one historical simulation in 1985 and running through 1998 along with corresponding counterfactual ensemble members where the Mt. Pinatubo eruption has been removed for use in detection and attribution method development. These ensembles are initialized early enough to create independent climate states in 1991 during the time of the Mt. Pinatubo eruption.
We have also developed novel simulation ensembles that limit the variability at the time of the Mt. Pinatubo eruption by initializing with a state similar to observed conditions in June 1991. These limited variability ensembles provide a way to compare more directly with observational data. For this ensemble set, we also have corresponding counterfactual members with no Mt. Pinatubo eruption and have generated additional ensembles varying the mass of the Mt. Pinatubo eruption by factors of 0.1, 0.3, 0.5, 0.7, 1.3, and 1.5 to evaluate the impact of varying eruption mass on downstream impacts.