Quantifying atmospheric transport, chemistry, and mixing using a newtrajectory-box model and a global atmospheric-chemistry GCM

[摘要] We present a novel method for the quantification of transport, chemistry, andmixing along atmospheric trajectories based on a consistent model hierarchy.The hierarchy consists of the new atmospheric-chemistry trajectory-box modelCAABA/MJT and the three-dimensional (3-D) global ECHAM/MESSyatmospheric-chemistry (EMAC) general circulation model. CAABA/MJT employs theatmospheric box model CAABA in a configuration using theatmospheric-chemistry submodel MECCA (M), the photochemistry submodel JVAL(J), and the new trajectory submodel TRAJECT (T), to simulate chemistry alongatmospheric trajectories, which are provided offline. With the samechemistry submodels coupled to the 3-D EMAC model and consistentinitial conditions and physical parameters, a unique consistency between thetwo models is achieved. Since only mixing processes within the 3-D model are excluded from the model consistency, comparisons of results fromthe two models allow to separate and quantify contributions of transport,chemistry, and mixing along the trajectory pathways. Consistency of transportbetween the trajectory-box model CAABA/MJT and the 3-D EMAC model isachieved via calculation of kinematic trajectories based on 3-D windfields from EMAC using the trajectory model LAGRANTO. The combination of thetrajectory-box model CAABA/MJT and the trajectory model LAGRANTO can beconsidered as a Lagrangian chemistry-transport model (CTM) moving isolatedair parcels. The procedure for obtaining the necessary statistical basis forthe quantification method is described as well as the comprehensivediagnostics with respect to chemistry.

The quantification method presented here allows to investigate thecharacteristics of transport, chemistry, and mixing in a grid-based3-D model. The analysis of chemical processes within thetrajectory-box model CAABA/MJT is easily extendable to include, forexample, the impact of different transport pathways or of mixingprocesses onto chemistry. Under certain prerequisites described here, theresults can be used to complement observations with detailed informationabout the history of observed air masses.

[学科分类] 天文学(综合)