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Neal Butchart and Ellis E. Remsberg


Data retrieved from the LIMS (Limb lnfrared Monitor of the Stratosphere) experiment are used 10 calculate daily isentropic distributions of Ertel's potential vorticity, ozone, water vapor and nitric acid at the 850 K level in the Northern Hemisphere stratosphere for the period 25 October 1978 through 2 April 1979. Systematic redistributions of the quasi-conservative tracers are investigated by following the evolutions of the horizontal projection of the areas enclosed by isopleths of tracer on the isentropic surface. If the horizontal velocity is nondivergent on an isentropic surface, the areas change in response to nonconservative processes and /or irreversible mixing to unresolvable scales and so provide a diagnostic for quantifying the net cited of these two processes. The effects of the seasonal variation of the solar heating on the areas are identified from the evolutions of the hemispheric means and, for the potential vorticity, from a comparison with an annual Mile integration of a zonally symmetric, general circulation model. Superimposed on the seasonal trends are changes in areas on shorter time scales, and the LIMS potential vorticity, ozone and water vapor distributions each show the distinctive “surf-zone, main–,vortex structure” described by McIntyre and Palmer. As winter progresses the main vortex decreases in size while the surf zone expands. The evidence of the observations, combined with estimates of the strength of the radiative processes acting on the potential vorticity field, indicates fairly convincingly that irreversible mixing is an important mechanism involved in the formation of the surf-zone, main-vortex structure, and the subsequent erosion in size of the vortex. In addition, there is evidence of strong diabatic cross-isentropic transport of air parcels in the surf zone acting to restore the large-scale gradients destroyed by the mixing. The only LIMS measured constituent for which mixing was not always the dominant mechanism of redistribution was nitric acid, and it is speculated that the effects of dynamically induced changes to the effective sources and sinks of nitric acid on the 850 K surface are overshadowing other processes, at least in late January and February. Implications to tracer transport studies are examined by using the isentropic potential vorticity field as a basis for calculating low resolution approximations to the Lagrangian-mean tracer mixing ratios. The results demonstrate the feasibility of the approach to the longer-species but indicate a need for further research to distinguish between dynamical and radiactive/photochemical effects.

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T. Miles, W. L. Grose, E. E. Remsberg, and G. Lingenfelser


The evolution of zonal wind and zonal wavenumber one (wave 1) in the Southern Hemisphere subpolar middle atmosphere is described for the period December 1978–May 1979 using temperature and ozone measurements from the Limb Infrared Monitor of the Stratosphere (LIMS) experiment.

In late December maximum zonal easterlies of ∼ −70 m s−1 are observed at 0.1 mb, 60°S. A zonal flow reversal occurs during late February and westerlies subsequently increase to 60–70 m s−1 in the upper stratosphere by April–May. LIMS zonal winds are compared with rocketsonde measurements and nadir sounder (derived) winds for summer and autumn. Although quantitative agreement is found at stratospheric levels, substantial discrepancies are evident in the mesosphere, most likely a reflection of sampling and resolution differences in the respective datasets.

Stationary and traveling wave 1 temperature disturbances (amplitudes ∼1–2 K at 60°S) are observed by LIMS during summer. The stationary wave is confined to the lower stratosphere near the level of zero zonal mean wind flow, whereas the traveling wave is prominent in the middle stratosphere, moves west at a rate similar to the zonal-mean wind, and exhibits a vertical-meridional structure similar to a P1 4 normal mode Rossby wave. A substantial intensification of wave 1 activity occurs during autumn (amplitudes ∼5–10 K), which is found to be associated with an upward-directed Eliassen–Palm flux near the subpolar tropopause level. Evidence relating wave 1 activity in the lower-middle stratosphere to the occurrence of zonal ozone perturbations of 10%–20% amplitude is presented for summer and autumn.

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C.B. Leovy, C-R. Sun, M.H. Hitchman, E.E. Remsberg, J.M. Russell, III, L.L. Gordley, J.C. Gille, and L.V. Lyjak


Data from the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) for the period 25 October 1978–28 May 1979 are used in a descriptive study of ozone variations in the middle stratosphere. It is shown that the ozone distribution is strongly influenced by irreversible deformation associated with large amplitude planetary-scale waves. This process, which has been described by McIntyre and Palmer as planetary wave breaking, takes place throughout the 3–30 mb layer, and poleward transport of ozone within this layer occurs in narrow tongues drawn out of the tropics and subtropics in association with major and minor warming events. Thew events complement the zonal mean diabatic circulation in producing significant changes in the total column amount of ozone.

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