Abstract
Abstract. CHIMERE is a chemistry-transport model designed for regional atmospheric composition. It can be used at a variety of scales from local to continental domains. However, due to the model design and its historical use as a regional model, major limitations had remained, hampering its use at hemispheric scale, due to the coordinate system used for transport as well as to missing processes that are important in regions outside Europe. Most of these limitations have been removed in the CHIMERE-2017 version, allowing its use in any region of the world and at any scale, from the scale of a single urban area up to hemispheric scale, with or without polar regions included. Other important improvements have been made in the treatment of the physical processes affecting aerosols and the emissions of mineral dust. From a computational point of view, the parallelization strategy of the model has also been updated in order to improve model numerical performance and reduce the code complexity. The present article describes all these changes. Statistical scores for a model simulation over continental Europe are presented, and a simulation of the circumpolar transport of volcanic ash plume from the Puyehue volcanic eruption in June 2011 in Chile provides a test case for the new model version at hemispheric scale.
Highlights
Deterministic chemistry-transport modeling is widely used for the analysis of pollution events, scenarios and forecast (Monks et al, 2009)
For regional air quality in the troposphere, several chemistry-transport models (CTMs) are currently developed and are able to include all types of emissions: anthropogenic, biogenic, mineral dust, sea salt, vegetation fires and volcanos
This induces some major simplifications of CHIMERE code, including reduction of inter-process communications related to the parallelization of the input/output processes, which were performed in a central way by the master process in previous model version
Summary
Deterministic chemistry-transport modeling is widely used for the analysis of pollution events, scenarios and forecast (Monks et al, 2009). The changes for the grid management are dedicated to build a CTM able to run over a hemispheric domains as well as for smaller regions anywhere in the world These developments required important changes in the model, as well as the improvement of many processes already included in the previous version: the Fast-JX module for realistic evaluation of the photolysis rates has been added and allows for the calculation of updated photolysis rates at each physical time step, including the optical effects of clouds and aerosols. The mineral dust emissions have been upgraded in order to estimate fluxes in any region This new version has been an opportunity to update the representation of chemical processes by giving the user the choice to use the SAPRC chemical mechanism, which is more widely used than the MELCHIOR chemical scheme developed for the CHIMERE model (Lattuati, 1997; Menut et al, 2013a).
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