Number of specific experiments
Knowledge-gap to be addressed
Stratospheric sulphur budget in volcanically quiescent conditions
1 mandatory +
20 year climatology to understand sources and sinks of stratospheric background aerosol, assessment of sulfate aerosol load under volcanically quiescent conditions
Transient stratospheric aerosol properties over the period 1998 to 2012 using different volcanic emission datasets
4 mandatory +3 optional experiments
recommended are 5 (see also Table 4 )
Evaluate models over the period 1998-2012 with different volcanic emission data sets
Understand drivers and mechanisms for observed stratospheric aerosol changes since 1998
Perturbation to stratospheric aerosol from SO2 emission appropriate for 1991 Pinatubo, 1982 El Chichón,1963, Agung
for each (x3) eruption (Control, median and 4 (2x2) of hi/lo deep/shallow (see also Table 6)
Assess how injected SO2 propagates through to radiative effects for different historical major tropical eruptions in the different interactive stratospheric aerosol models
Use stratospheric aerosol measurements to constrain uncertainties in emissions and gain new observationally-constrained volcanic forcing and surface area density datasets
Explore the relationship between volcanic emission uncertainties and volcanic forcing uncertainties
Perturbed parameter ensemble of runs to quantify uncertainty in each model’s predictions
7 experiments per parameter , where the number of parameters refers to the minimum (3), reduced (5) or standard (8) parameter set (see also Table 10)
3 per experimentC
280, (175, 280)
Intercompare Pinatubo perturbation to strat- aerosol properties with full uncertainty analysis over PPE run by each model.
Quantify sensitivity of predicted Pinatubo perturbation stratospheric aerosol properties and radiative effects to uncertainties in injection settings and model processes
Quantify and intercompare sources of uncertainty in simulated Pinatubo radiative forcing for the different complexity models.
A Each model will need to include an appropriate initialization and spin-up time for each ensemble member (~3-6 years depending on model configuration).
B As explained in the caption to Table 11 and section 3.4, models will need to restrict the PoEMS parameter-scaling to volcanically-enhanced air masses (either via total-sulphur-vmr threshold or passive volcanic SO2 tracer)
C Although the Pinatubo enhancement to the stratospheric aerosol layer remained apparent until 1997 (e.g. Wilson et al., 2008), whereas the HErSEA experiments will continue longer, the PoEMS analysis will require only 3 post-eruption years to be run, as this gives sufficient time after the peak aerosol to characterize decay timescales robustly (e.g. ASAP2006, chapter5) .