Development of a reduced chemical scheme for use in mesoscale meteorological models

A new Regional Lumped Atmospheric Chemical Scheme (ReLACS) is introduced. T his mechanism is intended to be valid for clean to polluted conditions. ReL ACS is derived from a new reactivity weighting approach which may be applie d to any atmospheric chemical scheme. In this work, ReLACS is based upon th e reduction of the regional atmospheric chemistry mechanism (RACM) (Stockwe ll ct al., 1997. Journal of Geophysical Research D22, 25847-25849) on a giv en moderately polluted emission scenario. However, sensitivity tests around this scenario show that ReLACS compares favorably with RACM, not only for ozone but also for other important atmospheric oxidants. The gain obtained from this lumping in the number of species allows ReLACS to be suitable to perform, otherwise costly, three dimensional pollution studies when coupled with mesoscale meteorological models. (C) 2000 Elsevier Science Ltd. All r ights reserved.