Assessment of the reduction methods used to develop chemical schemes: building of a new chemical scheme for VOC oxidation suited to three-dimensional multiscale HOsubx/sub-NOsubx/sub-VOC chemistry simulations

摘要

The objective of this work was to develop and assess an automatic procedureto generate reduced chemical schemes for the atmospheric photooxidation ofvolatile organic carbon (VOC) compounds. The procedure is based on (i) thedevelopment of a tool for writing the fully explicit schemes for VOCoxidation (see companion paper Aumont et al., 2005), (ii) the application ofseveral commonly used reduction methods to the fully explicit scheme, and(iii) the assessment of resulting errors based on direct comparison betweenthe reduced and full schemes.

The reference scheme included seventy emitted VOCs chosen to berepresentative of both anthropogenic and biogenic emissions, and theiratmospheric degradation chemistry required more than two million reactionsamong 350000 species. Three methods were applied to reduce the size of thereference chemical scheme: (i) use of operators, based on the redundancy ofthe reaction sequences involved in the VOC oxidation, (ii) grouping ofprimary species having similar reactivities into surrogate species and (iii)grouping of some secondary products into surrogate species. The number ofspecies in the final reduced scheme is 147, this being small enough forpractical inclusion in current three-dimensional models. Comparisons betweenthe fully explicit and reduced schemes, carried out with a box model forseveral typical tropospheric conditions, showed that the reduced chemicalscheme accurately predicts ozone concentrations and some other aspects ofoxidant chemistry for both polluted and clean tropospheric conditions.