Parameters | Minimum set | Reduced set | Standard set | Uncertainty range | |

1 | Injected SO2 mass | X | X | X | 5 Tg-S – 10 Tg-S |

2 | Mid-point height of 3km-thick injection | X | X | X | 18km – 30km |

3 | Latitudinal extent of the injection | X | X | X | Factor 0-1 to vary from 1-box injection at 15N (factor=0) to equator-to-15N (factor=1) * |

4 | Sedimentation velocity | X | X | Multiply model calculated velocity by a factor 0.5 to 2. | |

5 | SO2 oxidation scaling | X | X | Scale gas phase oxidation of SO2 by a factor 0.5 to 2 | |

6 | Nucleation rate of sulfate particles | X | Scale model calculated rate by a factor 0.5 to 2. | ||

7 | Sub-grid particle formation factor. | X | Emit fraction of SO2 as sulphuric acid particles formed at sub-grid-scale (0 to 10%) | ||

8 | Coagulation rate | X | Scale the model calculated rate by a factor 0.5 to 2. |

Groups will need to translate the 0-1 latitude-spread parameter into a sequence of fractional injections into all grid boxes between the equator and 15 °N. For example for a model with 2.5 degree latitude resolution, the relative injection in the 6 latitude bins between 0 and 15N would take the form [0,0,0,0,0,0,1] for extent factor=0, and [0.167,0.167, 0.167,0.167, 0.167,0.167] for extent factor=1. Injection ratios for intermediate values of the spread factor would be calculated by interpolation between these two end member cases.