Mixing and ozone loss in the 1999–2000 Arctic vortex: Simulations with the three‐dimensional Chemical Lagrangian Model of the Stratosphere (CLaMS)

Abstract

[1] The three-dimensional (3-D) formulation of the Chemical Lagrangian Model of the Stratosphere (CLaMS-3d) is presented that extends the isentropic version of CLaMS to cross-isentropic transport. The cross-isentropic velocities of the Lagrangian air parcels are calculated with a radiation module and by taking into account profiles of ozone and water vapor derived from a HALOE climatology. The 3-D extension of mixing maintains the most important feature of the 2-D version as mixing is mainly controlled by the horizontal deformations of the wind fields. In the 3-D version, mixing is additionally driven by the vertical shear in the flow. The impact of the intensity of mixing in the 3-D model formulation on simulated tracer distributions is elucidated by comparing observations of CH 4 , Halon-1211, and ozone from satellite, balloon, and ER-2 aircraft during the SOLVE/ THESEO-2000 campaign. CLaMS-3d simulations span the time period from early December 1999 to the middle of March 2000, with air parcels extending over the Northern Hemisphere in the vertical range between 350 and 1400 K. The adjustment of the CLaMS3d mixing parameters to optimize agreement with observations was obtained for strongly inhomogeneous, deformation-induced mixing that affects only about 10% of the air parcels per day. The optimal choice of the aspect ratio a defining the ratio of the mean horizontal and vertical separation between the air parcels was determined to be 250 for model configuration with a horizontal resolution r 0 = 100 km. By transporting ozone in CLaMS-3d as a passive tracer, the chemical ozone loss was inferred as the difference between the observed and simulated ozone profiles. The results show, in agreement with previous studies, a substantial ozone loss between 380 and 520 K with a maximum loss at 460 K of about 1.9 ppmv, i.e., of over 60% locally, from December to the middle of March 2000. During this period, the impact of isentropic mixing across the vortex edge outweighs the effect of the spatially inhomogeneous (differential) descent on the tracer/ ozone correlations in the vortex. Mixing into the vortex shifts the early winter reference tracer/ozone correlation to higher values, which may lead to an underestimate of chemical ozone loss, on average by 0.4 and 0.1 ppmv in the entire vortex and the vortex core, respectively.

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

“…Throughout the stratosphere (above about 300 hPa) potential temperature is used as vertical coordinate in the model, and vertical cross-isentropic velocity is deduced from the ERA-Interim forecast total diabatic heating rate . The Lagrangian transport model CLaMS has been shown to simulate the global stratospheric trace gas distributions well and even the small-scale structures and steep gradients therein [e.g., Konopka et al, 2004]. In particular, the multiyear simulation analyzed here has been shown to realistically represent transport of ozone and water vapor in the lower stratosphere [e.g., Konopka et al, 2010;Ploeger et al, 2013].…”

“…The Lagrangian transport of trace gases in CLaMS is based on three-dimensional air parcel forward trajectories and a parameterization of small-scale irreversible PLOEGER ET AL. mixing induced by deformations in the large-scale atmospheric flow [Konopka et al, 2004]. The model is driven with meteorological data from the ECMWF ERA-Interim reanalysis [Dee et al, 2011].…”

The Lagrangian chemistry and transport model ATLAS: validation of advective transport and mixing

“…The main concept of the model is similar to the CLaMS 3-D model (Konopka et al, 2004), which has a more sophisticated mixing parameterization compared to models like e.g. ATILLA or Collins et al (1997).…”

“…Some changes and improvements are introduced to the transport and mixing approach of CLaMS here, and their impact on the results is elucidated. The method of validation presented in Konopka et al (2004) is also analyzed, and some changes are proposed for a more robust calculation of the validation parameters. Finally, the model is used to infer values for the effective horizontal and vertical diffusion coefficients for the stratosphere, and results are compared with other studies.…”

“…Collins et al, 1997;Fairlie et al, 1999). The most prominent examples are the CLaMS model (McKenna et al, 2002;Konopka et al, 2004Konopka et al, , 2007) and the ATTILA model (Reithmeier and Sausen, 2002), which has recently been coupled to the General Circulation Model ECHAM (Stenke et al, 2009). The main focus of this model version is on a proper representation of the chemistry and transport of the stratosphere, although a basic troposphere is included.…”