Trajectory model studies of ClO<sub>x</sub> activation during the 1991/92 northern hemispheric winter

Lutman, E. R.; Pyle, J. A.; Jones, R. L.; Lary, D. J.; MacKenzie, A. R.; Kilbane-Dawe, I.; Larsen, N.; Knudsen, B. M.

doi:10.1029/93gl03045

Cited by 15 publications

(7 citation statements)

References 8 publications

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“…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.…”

Section: Modeling Approachmentioning

confidence: 99%

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

2002

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The freezing processes that may lead to the formation of solid phase polar stratospheric clouds (PSCs) have been examined to assess their winter‐long effects, especially denitrification, in a coupled microphysical/photochemical model. Trajectory simulations spanned from November 1999 to April 2000, using a large set of trajectories which provided representative coverage of the entire Arctic vortex through the period of PSC formation and ozone depletion. A freezing process occurring at temperatures above the ice frost point is shown to be necessary to explain both the occurrence of solid phase PSCs early in the winter and denitrification, especially without dehydration. If freezing only occurs below the ice frost point the primary contributor to denitrification is actually sedimentation of liquid phase PSC particles. The mechanism of a second freezing process, occurring above the ice frost point, can not yet be conclusively determined. Of the cases considered, heterogeneous freezing of the aerosol to form nitric acid trihydrate (NAT) particles best reproduced solid phase PSC formation and observations of widespread denitrification with limited dehydration. The simulations constrain the number of frozen particles to be near either 0.02% or 1% of the total aerosol number; values in between 0.02% and 1% produce more intense denitrification than observed, demonstrating that small changes in the number of frozen particles could exacerbate denitrification. However, this result was contingent upon assuming that the heterogeneous nuclei remain active, producing PSCs, throughout the winter. An idealized homogeneous freezing process was also able to produce NAT PSCs and denitrification (rates of 106–107 cm−3 s−1 compared favorably with data) but differed from observations in one key aspect: denitrification was more frequently accompanied by dehydration. Nitric acid dihydrate (NAD) particles were less effective than NAT at denitrification, but heterogeneous freezing of 0.1% of the aerosol yielded results marginally consistent with measurements. An important limitation, however, of all the scenarios considered is that they produced more intense and more widespread dehydration than was observed. This suggests that model minimum temperatures (from UK Meteorological Office analyses) were too cold by 1 to 3 K.

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Section: Modeling Approachmentioning

confidence: 99%

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

2002

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“…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.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2002

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[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.

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“…There is no mixing between air parcels and the results are not dependent on problems with diffusion and artificial mixing associated with the resolution and advection schemes of some global models. The integrations are also cheaper than global model integrations, allowing sensitivity studies to be performed (for example Lutman ½! al.…”

Section: Methodsmentioning

confidence: 99%

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

Lutman¹,

Pyle²,

Chipperfield³

et al. 1997

J. Geophys. Res.

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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.

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Trajectory model studies of ClO_x activation during the 1991/92 northern hemispheric winter

Cited by 15 publications

References 8 publications

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

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

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

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

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Trajectory model studies of ClOx activation during the 1991/92 northern hemispheric winter

Cited by 15 publications

References 8 publications

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

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

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

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

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Trajectory model studies of ClO_x activation during the 1991/92 northern hemispheric winter