Abstract
Abstract. ATLAS is a new global Lagrangian Chemistry and Transport Model (CTM), which includes a stratospheric chemistry scheme with 46 active species, 171 reactions, heterogeneous chemistry on polar stratospheric clouds and a Lagrangian denitrification module. Lagrangian (trajectory-based) models have several important advantages over conventional Eulerian models, including the absence of spurious numerical diffusion, efficient code parallelization and no limitation of the largest time step by the Courant-Friedrichs-Lewy criterion. This work describes and validates the stratospheric chemistry scheme of the model. Stratospheric chemistry is simulated with ATLAS for the Arctic winter 1999/2000, with a focus on polar ozone depletion and denitrification. The simulations are used to validate the chemistry module in comparison with measurements of the SOLVE/THESEO 2000 campaign. A Lagrangian denitrification module, which is based on the simulation of the nucleation, sedimentation and growth of a large number of polar stratospheric cloud particles, is used to model the substantial denitrification that occured in this winter.
Highlights
Lagrangian models have several advantages over grid-based Eulerian models, only few Lagrangian Chemistry and Transport Model (CTM) are in use so far, including the STOCHEM (e.g. Collins et al, 1997), ATTILA (e.g. Reithmeier and Sausen, 2002) and CLaMS (e.g. Konopka et al, 2004) models
This is the second part of the model description of the ATLAS model, which focusses on the stratospheric chemistry module
The winter was one of the coldest stratospheric winters on record, with one of the largest amounts of ozone loss measured so far (e.g. Rex et al, 2002). It was one of the few winters where substantial denitrification occured in the Northern Hemisphere (Popp et al, 2001), which prolonged the period of stratospheric ozone loss, and it saw the discovery of the so-called “nitric acid trihydrate (NAT) rocks” as the probable cause for this denitrification (Fahey et al, 2001)
Summary
Lagrangian models have several advantages over grid-based Eulerian models (e.g. no numerical diffusion, no negative species concentrations by transport, easy parallelization), only few Lagrangian CTMs are in use so far, including the STOCHEM (e.g. Collins et al, 1997), ATTILA (e.g. Reithmeier and Sausen, 2002) and CLaMS (e.g. Konopka et al, 2004) models. ATLAS is a new global Lagrangian CTM with a focus on the stratosphere This is the second part of the model description of the ATLAS model, which focusses on the stratospheric chemistry module. The winter was one of the coldest stratospheric winters on record, with one of the largest amounts of ozone loss measured so far (e.g. Rex et al, 2002) It was one of the few winters where substantial denitrification occured in the Northern Hemisphere (Popp et al, 2001), which prolonged the period of stratospheric ozone loss, and it saw the discovery of the so-called “NAT rocks” (large nitric acid trihydrate particles) as the probable cause for this denitrification (Fahey et al, 2001). A Supplement is provided with the paper, which includes figures of all comparisons of model data to measurements performed for this study
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