Scenarios for modeling multiphase tropospheric chemistry

Besides observational data model calculations are a very important tool for improving our understanding of multiphase chemistry in the troposphere. Be fore a chemical model can be used for that purpose it is necessary to show that the model does what it is intended to do. A protocol has been develope d that can be used as a basis for the verification of the numerics and the correct implementation of the chemical balance equations. The protocol defi nes meteorological parameters and initial conditions for a zerodimensional (box) model. Several scenarios cover the polluted as well as the remote mar ine and continental boundary layer and also the free troposphere. Calculati ons by different groups with different models and numerical solvers demonst rate that the protocol is clear and complete. The excellent agreement betwe en the results of all groups are a major step of verification of the partic ipating models. The scenarios may also serve as well documented base cases for sensitivity studies.