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Λογότυπος της Ευρωπαϊκής Επιτροπής
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The key difference between the design of Phase 1 and Phase 2 is that the models participating in Phase 1 were “stand-alone” or “offline” chemistry transport models (CTM) that required meteorology produced by meteorological models (MetM) as input, while the models participating in Phase 2 were on-line coupled or integrated CTMs and MetMs.

On-line identifies the property of the model to generate the meteorology that drives the transport within the model itself, therefore solving equations for momentum, radiation and heat at the same time as transport and chemical transformation of chemically active species.

This modelling approach leads to a higher level of complexity in model development, application and evaluation but at the same time also yields intrinsic consistency in the model results which is produced by the solution of a coherent set of equations and numerical methodologies.