Systematic reduction of complex tropospheric chemical mechanisms, Part II: Lumping using a time-scale based approach

[摘要] This paper presents a formal method of species lumping that can be appliedautomatically to intermediate compounds within detailed and complextropospheric chemical reaction schemes. The method is based on groupingspecies with reference to their chemical lifetimes and reactivity structures.A method for determining the forward and reverse transformations betweenindividual and lumped compounds is developed. Preliminary application to theLeeds Master Chemical Mechanism (MCMv2.0) has led to the removal of 734species and 1777 reactions from the scheme, with minimal degradation ofaccuracy across a wide range of test trajectories relevant to pollutedtropospheric conditions. The lumped groups are seen to relate to groups ofperoxy acyl nitrates, nitrates, carbonates, oxepins, substituted phenols,oxeacids and peracids with similar lifetimes and reaction rates with OH. Incombination with other reduction techniques, such as sensitivity analysis andthe application of the quasi-steady state approximation (QSSA), a reducedmechanism has been developed that contains 35% of the number of species and 40% of the number ofreactions compared to the full mechanism.This has led to a speed up of a factor of 8 in terms ofcomputer calculation time within box model simulations.

[学科分类] 大气科学