Variability of the subtropical “edges” in the stratosphere

Neu, J. L.; Sparling, L. C.; Plumb, R. Alan

doi:10.1029/2002jd002706

Cited by 44 publications

(92 citation statements)

References 55 publications

(96 reference statements)

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“…1 illustrates, there are regions of strong subtropical gradient on both sides of the equator, which persist throughout the year. Figure 4 shows their seasonal evolution at several stratospheric altitudes, as determined from six years of HALOE observations of CH 4 (Neu, 2000). The edge locations are remarkably consistent from year to year.…”

Section: Tropical Isolation (And Non-isolation)mentioning

confidence: 89%

“…The ''tropical region'' (i.e., the region bounded by the subtropical edges) migrates, most markedly at higher altitudes, into the summer hemisphere, qualitatively similar to the migration of maximum upwelling (Rosenlof 1995;Eluszkiewicz et al 1996). However, the location of the winter edge in fact corresponds more closely with the zero wind line than with the transition from upwelling to downwelling (Neu 2000;Neu et al 2002). This is consistent with calculations of ''effective diffusivity'' (Nakamura 1996) which show high values within the surf zone, decreasing sharply at the vortex and subtropical within the surf zone (schematic).…”

Section: Tropical Isolation (And Non-isolation)mentioning

confidence: 95%

“…The most compelling evidence of this comes from observations of anomalous vortex relationships between certain pairs of long-lived tracers (Michelson et al 1998;Kondo 1999;Plumb et al 2000;Rex et al 2000), whose only apparent explanation is that surf zone air is being mixed into the vortex. Indeed, it now appears that distinct compact relationships were established within the Arctic vortex by late winter of 2000 , implying also the presence of rapid mixing within (in addition to possible weak mixing into) the vortex.…”

Section: Tracers In the Vortexmentioning

confidence: 99%

“…However, it appears that the summer subtropical edge is not merely a survivor of wintertime formation, but is actively sustained by diabatic processes, especially at higher altitudes (Neu 2000). Evidence that the subtropical edges act in some sense as transport barriers, at least partly isolating the tropics from the vigorous stirring of the surf zone, comes from the observation that tracer-tracer relationships in the tropics are distinct from those of the surf zone (e.g., Plumb 1996;Volk et al 1996).…”

Section: Tropical Isolation (And Non-isolation)mentioning

confidence: 99%

“…Thus, it is not accurate to regard the tropical region as being completely isolated. Indeed, many studies have deduced similar time scales (most in the range 1-1.5 yr) for detrainment of surf zone air into the tropical lower stratosphere, on the basis of the observed budgets of chemical tracers (e.g., Avallone and Prather 1996;Volk et al 1996;Hermann et al 1998) or of age (Hall and Waugh 1997;Neu and Plumb 1999). Indeed, Hall and Waugh (1997) used simultaneous analysis of observations of age and of the tape recorder to make independent determinations of all components of transport in the region, which amongst other things allowed them to confirm that the effects of vertical diffusion are negligible (as had previously been assumed).…”

Section: Tropical Isolation (And Non-isolation)mentioning

confidence: 99%

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Stratospheric Transport

Plumb

2002

Journal of the Meteorological Society of Japan

315

301

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Improvements in our understanding of transport processes in the stratosphere have progressed hand in hand with advances in understanding of stratospheric dynamics and with accumulating remote and in situ observations of the distributions of, and relationships between, stratospheric tracers. It is convenient to regard the stratosphere as being separated into four regions: the summer hemisphere, the tropics, the wintertime midlatitude ''surf zone'', and the winter polar vortex. Stratospheric transport is dominated by mean diabatic advection (upwelling in the tropics, downwelling in the surf zone and the vortex) and, especially, by rapid isentropic stirring within the surf zone. These characteristics determine the global-scale distributions of tracers, and their mutual relationships. Despite our much-improved understanding of these processes, many chemical transport models still appear to exhibit significant shortcomings in simulating stratospheric transport, as is evidenced by their tendency to underestimate the age of stratospheric air.

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Section: Tropical Isolation (And Non-isolation)mentioning

confidence: 89%

Section: Tropical Isolation (And Non-isolation)mentioning

confidence: 95%

Section: Tracers In the Vortexmentioning

confidence: 99%

Section: Tropical Isolation (And Non-isolation)mentioning

confidence: 99%

Section: Tropical Isolation (And Non-isolation)mentioning

confidence: 99%

See 3 more Smart Citations

Stratospheric Transport

Plumb

2002

Journal of the Meteorological Society of Japan

315

301

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The role of midlatitude mixing barriers in creating the annual variation of total ozone in high northern latitudes

et al. 2014

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Data from the HIgh Resolution Dynamics Limb Sounder (HIRDLS), the Microwave Limb Sounder (MLS), and the Whole Atmosphere Community Climate Model (WACCM) are used to investigate the annual variation of total column ozone in high northern latitudes. Downward transport of ozone-rich air by the residual mean circulation during autumn and winter bends ozone isopleths down and increases the high-latitude ozone amounts, leading to an ozone maximum at the end of the winter. During the summer months eddy mixing acts to restore pre-fall distributions of ozone. In this study the large-scale mixing in the lower stratosphere is analyzed using Nakamura's (1996) equivalent length formulation with observed and simulated ozone. The analysis of ozone mixing is performed in the tracer equivalent latitude-potential temperature coordinate system. Steep latitudinal gradients of ozone isopleths below about 500 K occur during the winter, where there are minima in the equivalent length, indicating barriers to mixing at 30°N-40°N. This transport barrier allows large ozone maxima to develop poleward of it. The barrier disappears over the summer, permitting latitudinal mixing of the high ozone air. Above 500 K mixing is more effective during the winter, so a large winter maximum does not occur. In both midlatitude and high latitude the lower stratospheric layer from 330 to 500 K doubles its ozone content from autumn to spring, compared with much smaller changes in the layer from 500 to 650 K. Our results confirm that the presence of the winter transport barrier in the lower stratosphere controls the seasonal variation of total ozone.

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Interannual variability in effective diffusivity in the upper troposphere/lower stratosphere from reanalysis data

Ábalos

Legras

Shuckburgh

2016

Quart J Royal Meteoro Soc

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The effective diffusivity based on passive tracer advection is used to evaluate the long-term mixing properties for the period 1980-2012 in the lower stratosphere and upper troposphere (UTLS) using data from the ERA-Interim reanalysis. The regions of strongest interannual variability in effective diffusivity coincide with the regions of strong climatological mixing, such as the winter and spring midlatitude stratosphere, the polar lowermost stratosphere and around the edge of the subtropical jets (especially in summer). The annular modes dominate the variability in the winter polar vortices, and the Quasi-Biennial Oscillation in the tropical stratosphere. El Niño/Southern Oscillation modulates the strength of mixing across the subtropical jets, and has a significant impact on mixing in the summer subtropical lower stratosphere. Long-term trends show a vertical shift in the mixing consistent with the effect of ozone depletion on the zonal wind in the austral summer polar stratosphere. Other significant trends include increased mixing in the austral surf zone and a dipolar pattern in the boreal summer and autumn, with mixing increased on the equatorward part of the subtropical jet and reduced just above. The results are highly consistent with those from the JRA-55 reanalysis when the same horizontal resolution is used. The calculations are also qualitatively consistent with effective diffusivity obtained directly from the potential vorticity field and, in the UTLS, they are broadly consistent with those obtained from the ozone field.

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Variability of the subtropical “edges” in the stratosphere

Cited by 44 publications

References 55 publications

Stratospheric Transport

Stratospheric Transport

The role of midlatitude mixing barriers in creating the annual variation of total ozone in high northern latitudes

Interannual variability in effective diffusivity in the upper troposphere/lower stratosphere from reanalysis data

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