A new Chemical Lagrangian Model of the Stratosphere (CLaMS) 1. Formulation of advection and mixing

Abstract

[1] Recent satellite observations and dynamical studies have demonstrated the existence of filamentary structures in chemical tracer fields in the stratosphere. It is also evident that such features are often below the spatial resolution of the highest-resolution Eulerian models that have been used up to the present time. These observations have motivated the development of a novel Chemical Lagranigan Model of the Stratosphere (CLaMS) that is based on a Lagrangian transport of tracers. The description of CLaMS is divided into two parts: Part 1 (this paper) concentrates on the Lagrangian dynamics, i.e., on the calculation of trajectories and on a completely new mixing algorithm based on a dynamically adaptive grid, while part 2 describes the chemical integration and initialization procedure. The mixing of different air masses in CLaMS is driven by the large-scale horizontal flow deformation and takes into account the mass exchange between the nearest neighbors determined by Delaunay triangulation. Here we formulate an isentropic, i.e., two-dimensional version of the model and verify the mixing algorithm using tracer distributions measured during the space shuttle CRISTA-1 experiment where highly resolved stratospheric structures were observed in early November 1994. A comparison of the measured Southern Hemispheric N 2 O distribution with CLaMS results allows the intensity of simulated mixing to be optimized. The long-term robustness of the transport scheme is investigated in a case study of the 1996-1997 Northern Hemisphere polar vortex. This study further provides a dynamical framework for investigations of chemical arctic ozone destruction discussed in part 2.

Quantifying pollution transport from the Asian monsoon anticyclone into the lower stratosphere

“…We quantify air mass transport from the Asian monsoon anticyclone using simulations with the Lagrangian chemistry transport model CLaMS (McKenna et al, 2002;Konopka et al, 2004;Pommrich et al, 2014). CLaMS uses an isentropic vertical coordinate throughout the UTLS, and the model transport is driven with horizontal winds and total diabatic heating rates from European Centre of MediumRange Weather Forecasts (ECMWF) ERA-Interim reanalysis (Dee et al, 2011).…”

Satellite observations of cirrus clouds in the Northern Hemisphere lowermost stratosphere

“…Additional to advection by winds, irreversible small-scale mixing between air parcels induced by the deformation of the large-scale flow is considered in the model (McKenna et al, 2002a;Konopka et al, 2004). The mixing intensity is controlled by the local Lyapunov coefficient of the flow, thus leading to stronger mixing in regions of large flow deformations.…”

Variability of stratospheric mean age of air and of the local effects of residual circulation and eddy mixing

“…Mean age of air has been simulated with the Chemical Lagrangian Model of the Stratosphere (CLaMS) [McKenna et al, 2002] for the period 1988-2013, after initialization from a monthly zonal mean climatology based on the MIPAS AoA observations of Stiller et al [2008] and an 8 year spin-up period (with perpetual 1988 conditions). We ensured independence of our results from the initialization by carrying out an identical simulation for the 2002-2012 period and comparing the two simulations during this period, ensuring that both simulations produce comparable results.…”

“…In this paper, we simulate global stratospheric AoA with the Lagrangian chemistry transport model CLaMS (Chemical Lagrangian Model of the Stratosphere) [McKenna et al, 2002] driven by European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim meteorological data for the period 1988-2013. We particularly focus on comparisons to the satellite observations from the MIPAS instrument, available during the last decade.…”