References

ACPD

Atmospheric Chemistry and Physics Discussions

ACPD

1680-7375

Copernicus GmbH

Göttingen, Germany

10.5194/acpd-8-10627-2008

Mixing processes and exchanges in the tropical and the subtropical UT/LS

James

¹ Legras

Laboratoire de Météorologie Dynamique UMR 8539, Paris, France

04 06 2008

8 3 10627 10664

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Both in situ measurements and satellite observations indicate evidence of mixing in the upper troposphere (UT) and the lower-stratosphere (LS). In this study, the measurements performed during the Pre-AVE and Costa-Rica AVE campaigns are analysed with diffusive back-trajectories to assess mixing properties in the tropical and the subtropical UT/LS. A description of cross-tropopause pathways and mixing time scales is provided. In the subtropics, Troposphere-Stratosphere mixing processes are found to differ in the vicinity of the tropopause and at higher altitudes. Below 350 K, the mixing line observed during Pre-AVE is shown to result from fast and local cross-tropopause irreversible exchange, involving two initially distant air masses with distinct chemical compositions. For measurements located above 350 K, mixing of the tropospheric air in the subtropical stratosphere occurs over a period of a month, the origins of the tropospheric source being localised in the tropical UT and the tropical boundary layer. In the tropics, quantitative reconstructions of CO and O3 profiles above 360 K are obtained for one month back-trajectories calculations, pointing out that long term mixing is essential to determine the chemical composition in the tropical ascent. In particular, the existence of two-way meridional irreversible exchanges between 360 and 450 K is found to export tropical air in the subtropical stratosphere and to entrain old stratospheric air in the tropical ascent. Calculations of the Lagrangian mean age of air is shown to be in qualitative agreement with the CO2 observations and diabatic calculations.

References 1

Andrews, A E., Boering, K A., Wofsy, S C., Daube, B C., Jones, D B., Alex, S., Loewenstein, M., Podolske, J R., and Strahan, S E.: Empirical age spectra for the lower tropical stratosphere from in situ observations of \protectCO2: \protectQuantitative evidence for a sub-tropical barrier to horizontal transport, J Geophys. Res., 106, 32 295–32 314, \doi10.1029/2001JD000465, 2001.

Appenzeller, C., Holton, J R., and Rosenlof, K H.: Seasonal variation of mass transport across the tropopause, J Geophys. Res., 101, 15 071–15 078, \doi10.1029/96JD00821, 1996.

Chen, P.: Isentropic cross-tropopause mass exchange in the extratropics, J Geophys. Res., 100, 16 661–16 674, \doi10.1029/95JD01264, 1995.

Daube, B C., J., Boering, K A., Andrews, A E., and Wofsy, S C.: A High-Precision Fast-Response Airborne \protectCO2 Analyzer for In Situ Sampling from the Surface to the Middle Stratosphere, J. Atmos. Ocean. Tech., 19, 1532–1543, \doi10.1175/1520-0426(2002)019<1532:AHPFRA>2.0.CO;2, 2002.

Desler, A E. and Scherwood, S C.: Effect of convection on the summertime extratropical lower stratosphere, J Geophys. Res., 109, D23301, \doi10.1029/2004JD005209, 2004.

Fischer, H., Wienhold, F G., Hoor, P., Bujok, O., Schiller, C., Siegmund, P., Ambaum, M., Scheeren, H A., and Lelieveld, J.: Tracer correlations in the northern high latitude lowermost stratosphere: \protectInfluence of cross-tropopause mass exchange, Geophys. Res. Lett., 27, 97–100, \doi10.1029/1999GL010879, 2000.

Grewe, V., Reithmeier, C., and Shindell, D.: Dynamic-chemical coupling of the upper troposphere and lower stratosphere region, Chemosphere, 47, 851–861, \doi10.1016/S0045-6535(02)00038-3, 2002.

Haynes, P H. and Shuckburgh, E.: Effective diffusivity as a diagnostic of atmospheric transport. \mboxPart I: stratosphere, J Geophys. Res., 105, 22 777–22 794, \doi10.1029/2000JD900093, 2000a.

Haynes, P H. and Shuckburgh, E.: Effective diffusivity as a diagnostic of atmospheric transport. \mboxPart II: troposphere and lower stratosphere, J Geophys. Res., 105, 22 795–22 810, \doi10.1029/2000JD900092, 2000b.

Haynes, P H., Scinocca, J F., and Greenslade, M D.: Formation and maintenance of the extratropical tropopause by baroclinic eddies, Geophys. Res. Lett., 28, 4179–4182, \doi10.1029/2001GL013485, 2001.

Hoor, P., Fischer, H., Lange, L., Lelieveld, J., and Brunner, D.: Seasonal variations of a mixing layer in the lowermost stratosphere as identified by the \protectCO-O3 correlation from in situ measurements, J Geophys. Res., 107, 4044–4060, \doi10.1029/2000JD000289, 2002.

Hoor, P., Gurk, C., Brunner, D., Hegglin, M I., Wernli, H., and Fischer, H.: Seasonality and extent of extratropical \protectTST derived from in-situ \protectCO measurements during \protectSPURT, Atmos. Chem. Phys., 4, 1427–1442, 2004.

Hoor, P., Fischer, H., and Lelieveld, J.: Tropical and extratropical tropospheric air in the lowermost stratosphere over \protectEurope: \mboxA \mboxCO-based budget, Geophys. Res. Lett., 32, L13812, \doi10.1029/2005GL022495, 2005.

Konopka, P., Günther, G., Müller, R., dos Santos, F H S., Schiller, C., Ravegnani, F., Ulanovsky, A., Schlager, H., Volk, C M., Viciani, S., Pan, L L., McKenna, D.-S., and Riese, M.: Contribution of mixing to upward transport across the tropical tropopause layer (TTL), Atmos. Chem. Phys., 7, 3285–3308, 2007.

Lefèvre, F., Brasseur, G P., Folkins, I., Smith, A K., and Simon, P.: Chemistry of the 1991–1992 stratospheric winter: \protectThree-dimensional model simulations, J Geophys. Res., 99, 8183–8195, \doi10.1029/93JD03476, 1994.

Lefèvre, F., Figarol, F., Carslaw, K S., and Peter, T.: The 1997 \protectArctic ozone depletion quantified from three-dimensional model simulations, Geophys. Res. Lett., 25, 2425–2428, \doi10.1029/98GL51812, 1998.

Legras, B., Pisso, I., Berthet, G., and Lefèvre, F.: Variability of the \protectLagrangian turbulent diffusion in the lower stratosphere, Atmos. Chem. Phys., 5, 1605–1622, 2005.

Loewenstein, M., Jost, H.-J., Grose, J., Eilers, J., Lynch, D., Jensen, S., and Marmie, J.: Argus: \protectA new instrument for the measurement of the stratospheric dynamical tracers, \protectN2O and \protectCH4, Spectrochim. Acta A, 58, 2329–2345, 2002.

Lopez, J P., Fridlind, A M., Jost, H.-J., Loewenstein, M., Ackerman, A S., Campos, T L., Weinstock, E M., Sayres, D S., Smith, J B., Pittman, J V., Hallar, A G., Avallone, L M., Davis, S M., and Herman, R L.: CO signatures in subtropical convective clouds and anvils during \protectCRYSTAL-FACE: \protectAn analysis of convective transport and entrainment using observations and a cloud-resolving model, J Geophys. Res., 111, D09305, \doi10.1029/2005JD006104, 2006.

Mote, P W., Rosenlof, K H., M Mclntyre, M E., Carr, E S., Gille, J C., Holton, J R., Kinnersley, J S., Pumphrey, H C., Russell~III, J M., and Waters, J W.: An atmospheric tape recorder: \protectThe imprint of tropical tropopause temperatures on stratospheric water vapor, J Geophys. Res., 101, 3989–4006, 1996.

Mullendore, G L., Durran, D R., and Holton, J R.: Cross-tropopause tracer transport in midlatitude convection, J Geophys. Res., 110, D06113, \doi10.1029/2004JD0050590, 2005.

Neu, J L. and Plumb, R A.: Age of air in a "leaky pipe" model of stratospheric transport, J Geophys. Res., 104, 19 243–19 255, \doi10.1029/1999JD900251, 1999.

Pan, L L., Randel, W J., Gary, B L., Mahoney, M J., and Hintsa, E J.: Definition and sharness of the extratropical tropopause: \protectA trace gas perspective, J Geophys. Res., 109, D23103, \doi10.1029/2004JD004982, 2004.

Pan, L L., Konopka, P., and Browell, E V.: Observations and model simulations of mixing near the extratropical tropopaus, J Geophys. Res., 111, D05106, \doi10.1029/2005JD006480, 2006.

Park, S., Jimenez, R., Daube, B C., Pfister, L T., Conway, T J., Gottlieb, E W., Chow, V Y., Curran, D J., Matross, D M., Bright, A., Atlas, E L., Bui, T P., Gao, R.-S., Twohy, C H., and Wofsy, S. C.: The \protectCO2 tracer clock for the Tropical Tropopause Layer, Atmos. Chem. Phys., 7, 3989–4000, 2007.

Patmore, N. and Toumi, R.: An entropy-based measure of mixing at the tropopause, Q J R. Meteorol. Soc., 132, 1949–1960, 2006.

Pisso, I. and Legras, B.: Turbulent vertical diffusivity in the sub-tropical stratosphere, Atmos. Chem. Phys., 8, 697–707, 2008.

Plumb, R A.: Tracer-tracer relationships in the stratosphere, Rev. Geophys., 45, RG4005, doi:10.1029/2005RG000179, 2007.

Proffitt, M H., Kelly, K K., Powell, J. A., Gary, B L., Loewenstein, M., Podolske, J R., Strahan, S E., and Chan, K R.: Evidence for diabatic cooling and poleward transport within and around the 1987 \protectAntarctic ozone hole, J Geophys. Res., 94, 16 797–16 813, \doi10.1029/89JD00905, 1989.

Randel, W J., Park, M., Wu, F., and Livesey, N.: A Large Annual Cycle in Ozone above the Tropical Tropopause Linked to the Brewer Dobson Circulation, J Atmos. Sci., 64, 4479–4488, \doi10.1175/2007JAS2409.1, 2007.

Rosenlof, K H. and McCormick, M P.: Hemispheric asymmetries in water vapor and inferences about transport in the lower stratosphere, J Geophys. Res., 102, 13 213–13 234, \doi10.1029/97JD00873, 1997.

Shapiro, M A.: Turbulent mixing within tropopause folds as a mechanism for the exchange of chemical constituents between the troposphere and the stratosphere, J Atmos. Sci., 37, 994–1004, \doi10.1175/1520-0469(1980)037<0994:TMWTFA>2.0.CO;2, 1980.

Stohl, A., Forster, C., Frank, A., and Wotawa, G.: Technical note: The Lagrangian particle dispersion model \protectFLEXPART version 6.2, Atmos. Chem. Phys., 6, 2461–2474, 2005.

Volk, C M., Elkins, J W., Fahey, D W., Salawitch, R J Dutton, G S., Gilligan, J M., Proffitt, M H., Loewenstein, M., Podolske, J R., Minschwaner, K., Margitan, J J., and Chan, K R.: Quantifying transport between the tropical and mid-latitude lower stratosphere, Science, 272, 1763–1768, 1996.

Waugh, D W.: Seasonal variation of isentropic transport out of the tropical stratosphere, J Geophys. Res., 101, 4007–4023, \doi10.1029/95JD03160, 1996.

Waugh, D W. and Hall, T M.: Age of stratospheric air: theory, observations, and models, Rev. Geophys., 40, \doi10.1029/2000RG000101, 2002.

Waugh, D W., Plumb, R A., Elkins, J W., Fahey, D W., Boering, K A., Dutton, G S., Volk, C M., Keim, E., Gao, R.-S., Daube, B C., Wofsy, S C., Lowenstein, M., Podolske, J R., Chan, K R., Proffitt, M H., Kelly, K K., Newman, P A., and Lait, L R.: Mixing of polar air into middle latitudes as revealed by tracer-tracer scatter plots, J Geophys. Res., 102, 13 119–13 134, \doi10.1029/96JD03715, 1997.

Wernli, H. and Bourqui, M.: A \protectLagrangian 1-year climatology of (deep) cross-tropopause exchange in the extratropical \protectNorthern \protectHemisphere, J Geophys. Res., 107, 4021, \doi10.1029/2001JD000812, 2002.