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During the CRISTA-1 mission three pronounced fingerlike structures reachingfrom the lower latitudes to the mid-latitudes, so-called streamers, wereobserved in the measurements of several trace gases in early November 1994. Asimulation of these streamers in previous studies employing the KASIMA(Karlsruhe Simulation Model of the Middle Atmosphere) and ROSE (Research onOzone in the Stratosphere and its Evolution) model, both being Eulerianmodels, show that their formation is due to adiabatic transport processes.Here, the impact of mixing on the development of these streamers isinvestigated. These streamers were simulated with the CLaMS model (ChemicalLagrangian Model of the Stratosphere), a Lagrangian model, using N<sub>2</sub>O aslong-lived tracer. Using several different initialisations the results werecompared to the KASIMA simulations and CRISTA (Cryogenic InfraredSpectrometer and Telescope for the Atmosphere) observations. Further, sincethe KASIMA model was employed to derive a 9-year climatology, the quality ofthe reproduction of streamers from such a study was tested by the comparisonof the KASIMA results with CLaMS and CRISTA. The streamers are reproducedwell for the Northern Hemisphere in the simulations of CLaMS and KASIMA forthe 6 November 1994. However, in the CLaMS simulation a strongerfilamentation is found while larger discrepancies between KASIMA and CRISTAwere found especially for the Southern Hemisphere. Further, compared to theCRISTA observations the mixing ratios of N<sub>2</sub>O are in general underestimatedin the KASIMA simulations. An improvement of the simulations with KASIMA wasobtained for a simulation time according to the length of the CLaMSsimulation. To quantify the differences between the simulations with CLaMSand KASIMA, and the CRISTA observations, the probability density functiontechnique (PDF) is used to interpret the tracer distributions. While in thePDF of the KASIMA simulation the small scale structures observed by CRISTAare smoothed out due to the numerical diffusion in the model, the PDFsderived from CRISTA observations can be reproduced by CLaMS by optimising themixing parameterisation. Further, this procedure gives information onsmall-scale variabilities not resolved by the CRISTA observations

Intercomparison between Lagrangian and Eulerian simulations of the development of mid-latitude streamers as observed by CRISTA