Three‐dimensional studies of the 1991/1992 northern hemisphere winter using domain‐filling trajectories with chemistry

Abstract

We describe a new and computationally efficient technique for global three‐dimensional modeling of stratospheric chemistry. This technique involves integrating a photochemical package along a large number of independent trajectories to produce a Lagrangian view of the atmosphere. Although Lagrangian chemical modeling with trajectories is an established procedure, this extension of integrating chemistry along a large number of domain‐filling trajectories is a novel technique. This technique is complementary to three‐dimensional Eulerian chemical transport modeling and avoids spurious mixing caused by low resolutions or diffusive transport schemes in these models. We illustrate the technique by studying the chlorine activation in the Arctic winter lower stratosphere. A photochemical model was integrated along large ensembles of calculated trajectories between 20 and 100 mbar for the 1991/1992 winter in order to produce a three‐dimensional chemical picture. Large amounts of chlorine was activated at low altitudes (80 to 100 mbar) as well as altitudes near 50 mbar. This activated air was well contained at all levels, with little indication of mixing into lower latitudes. Model results for early January 1992 were compared to daily Microwave Limb Sounder (MLS) ClO observations at 465 K. The structure and evolution of the activated chlorine was well reproduced, giving faith in the technique, although absolute modeled ClO amounts were smaller than the MLS data. A larger number of domain‐filling isentropic trajectories were also run at 475 K to produce a higher‐resolution picture of vortex evolution in late January 1992. The model successfully reproduced the wave breaking events which characterized this period causing transport of activated air to lower latitudes.

Comparison of ER‐2 aircraft and POAM III, MLS, and SAGE II satellite measurements during SOLVE using traditional correlative analysis and trajectory hunting technique

“…The agreement between remote sensing values of ClO in a box 400 × 400 × 4 km 3 and very accurate in situ ER‐2 measurements is good. It is clear that lower values of MLS ClO in v.5 compared with their values from the previous versions mitigate a concern about their positive bias raised previously by modelers [e.g., Chipperfield et al , 1996; Lutman et al , 1997] and mentioned by Waters et al [1996]. Since chlorine monoxide is a key ozone depleting species, accurate measurements of ClO and their agreement with models are crucial for our understanding of the changes in the global ozone layer.…”

Microphysical modeling of the 1999–2000 Arctic winter: 1. Polar stratospheric clouds, denitrification, and dehydration

“…This ensemble of trajectories was generated to provide horizontal and vertical coverage of the whole vortex throughout the winter, thus allowing the three‐dimensional evolution of the vortex to be examined. Similar sets of trajectories have been used in previous studies to represent the overall behavior of the Arctic vortex [ Newman et al , 1993; Lutman et al , 1994, 1997] or other regions of the stratosphere [ Fairlie et al , 1999; Pierce et al , 1999; Schoeberl et al , 1998, 2000]. No mixing or other interaction among the trajectories is taken into account in the simulations.…”

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

“…The first attempts to simulate stratospheric chemistry along multiple trajectories derived from stratospheric wind analysis were reported by Austin et al [1989]. As computer power has increased with time, it has become possible to simulate stratospheric photochemistry along progressively greater numbers of trajectories [ Lutman et al , 1994, 1997]. These techniques avoid the numerical diffusion across the grid box boundaries that inevitably arise with Eulerian schemes [ Rood , 1987; Tan et al , 1998] but fail to introduce any representation of mixing.…”