Refinements in the use of equivalent latitude for assimilating sporadic inhomogeneous stratospheric tracer observations, 1: Detecting transport of Pinatubo aerosol across a strong vortex edge

Article, Other literature type English OPEN
Good, P. ; Pyle, J. (2004)
  • Publisher: European Geosciences Union
  • Journal: (issn: 1680-7324)
  • Related identifiers: doi: 10.5194/acp-4-1823-2004
  • Subject: [ SDU.OCEAN ] Sciences of the Universe [physics]/Ocean, Atmosphere
    arxiv: Astrophysics::Galaxy Astrophysics | Physics::Geophysics | Physics::Atmospheric and Oceanic Physics

International audience; The use of PV equivalent latitude for assimilating stratospheric tracer observations is discussed ? with particular regard to the errors in the equivalent latitude coordinate, and to the assimilation of sparse data. Some example measurements are assimilated: they sample the stratosphere sporadically and inhomogeneously. The aim was to obtain precise information about the isentropic tracer distribution and evolution as a function of equivalent latitude. Precision is important, if transport across barriers like the vortex edge are to be detected directly. The main challenges addressed are the errors in modelled equivalent latitude, and the non-ideal observational sampling. The methods presented allow first some assessment of equivalent latitude errors and a picture of how good or poor the observational coverage is. This information determines choices in the approach for estimating as precisely as possible the true equivalent latitude distribution of the tracer, in periods of good and poor observational coverage. This is in practice an optimisation process, since better understanding of the equivalent latitude distribution of the tracer feeds back into a clearer picture of the errors in the modelled equivalent latitude coordinate. Error estimates constrain the reliability of using equivalent latitude to make statements like "this observation samples air poleward of the vortex edge'" or that of more general model-measurement comparisons. The approach is demonstrated for ground-based lidar soundings of the Mount Pinatubo aerosol cloud, focusing on the 1991?1992 arctic vortex edge between 475?520 K. Equivalent latitude is estimated at the observation times and locations from Eulerian model tracers initialised with PV and forced by UK Meteorological Office analyses. With the model formulation chosen, it is shown that tracer transport of a few days resulted in an error distribution that was much closer to Gaussian form, although the mean error was not significantly affected. The analysis of the observations revealed a small amount of irreversible transport of aerosol across the vortex edge during late January 1992, coincident with a strongly disturbed vortex.
  • References (22)
    22 references, page 1 of 3

    4, 635-666, 2004 Allen, D. R. and Nakamura, N.: Tracer equivalent latitude: A diagnostic tool for isentropic transport studies, J. Atmos. Sci., 60, 287-304, 2003. 638 Beyerle, G. and Neuber, R.: The stratospheric aerosol content above Spitsbergen during winter 1991/92, Geophys. Res. Lett., 21, 1291-1294, 1994. 660

    15 Bohren, C. and Huffman, D.: Scattering and Absorption of Light by Small Particles, Wiley, New York, 1981. 642 Borrmann, S., Dye, J. E., Baumgardner, D., Proffitt, M. H., Margitan, J. J., Wilson, J. C., Jonsson, H. H., Brock, C. A., Loewenstein, M., Podolske, J. R., and Ferry, G. V.: Aerosols as dynamical tracers in the lower stratosphere - ozone versus aerosol correlation after the

    20 Mount-Pinatubo eruption, J. Geophys. Res.-Atmos., 100, 11 147-11 156, 1995. 647 Brock, C. A., Jonsson, H. H., Wilson, J. C., Dye, J. E., Baumgardner, D., Borrmann, S., Pitts, M. C., Osborn, M. T., Decoursey, R. J., and Woods, D. C.: Relationships between optical extinction, backscatter and aerosol surface and volume in the stratosphere following the eruption of Mt-Pinatubo, Geophys. Res. Lett., 20, 2555-2558, 1993. 642

    25 Browell, E. V., Butler, C. F., Ismail, S., Robinette, P. A., Carter, A. F., Higdon, N. S., Toon, O. B., Schoeberl, M. R., and Tuck, A. F.: Airborne lidar observations in the wintertime Arctic stratosphere - polar stratospheric clouds, Geophys. Res. Lett., 17, 385-388, 1990. 643 Butchart, N. and Remsberg, E. E.: The area of the stratospheric polar vortex as a diagnostic for tracer transport on an isentropic surface, J. Atmos. Sci., 43, 1319-1339, 1986. 637 Chazette, P., David, C., Lefrere, J., Godin, S., Pelon, J., and Megie, G.: Comparative lidar study of the optical, geometrical, and dynamical properties of stratospheric post-volcanic aerosols, following the eruptions of El-Chichon and Mount-Pinatubo, J. Geophys. Res.-Atmos., 100, 23 195-23 207, 1995. 660

    5 Chipperfield, M. P.: Multiannual simulations with a three-dimensional chemical transport model, J. Geophys. Res., 104, 1781-1805, 1999. 641 Chipperfield, M. P. and Jones, R. L.: Relative influences of atmospheric chemistry and transport on Arctic ozone trends, Nature, 400, 551-554, 1999. 637 Deshler, T.: In-situ measurements of Pinatubo aerosol over Kiruna on 4 days between 18

    10 January and 13 February 1992, Geophys. Res. Lett., 21, 1323-1326, 1994. 642, 647 Deshler, T., Johnson, B. J., and Rozier, W. R.: Balloonborne measurements of Pinatubo aerosol during 1991 and 1992 at 41◦ N - vertical profiles, size distribution, and volatility, Geophys. Res. Lett., 20, 1435-1438, 1993. 642, 647 Digirolamo, P., Cacciani, M., Disarra, A., Fiocco, G., and Fua, D.: Lidar observations of the

    15 Pinatubo aerosol layer at Thule, Greenland, Geophys. Res. Lett., 21, 1295-1298, 1994. 660 Dragani, R., Redaelli, G., Visconti, G., Mariotti, A., Rudakov, V., MacKenzie, A. R., and Stefanutti, L.: High-resolution stratospheric tracer fields reconstructed with Lagrangian techniques: A comparative analysis of predictive skill, J. Atmos. Sci., 59, 1943-1958, 2002. 638

    20 Esler, J. G., Polvani, L. M., and Plumb, R. A.: On the mix-down times of dynamically active potential vorticity filaments, Geophys. Res. Lett., 26, 2953-2956, 1999. Evans, M. J., Shallcross, D. E., Law, K. S., Wild, J. O. F., Simmonds, P. G., Spain, T. G., Berrisford, P., Methven, J., Lewis, A. C., McQuaid, J. B., Pilling, M. J., Bandy, B. J., Penkett, S. A., and Pyle, J. A.: Evaluation of a Lagrangian box model using field measurements from

    25 EASE (Eastern Atlantic Summer Experiment) 1996, Atmos. Environ., 34, 3843-3863, 2000. 638 Fairlie, T. D., Pierce, R. B., Grose, W. L., Lingenfelser, G., Loewenstein, M., and Podolske, J. R.: Lagrangian forecasting during ASHOE/MAESA: Analysis of predictive skill for analyzed and reverse-domain-filled potential vorticity, J. Geophys. Res.-Atmos., 102, 13 169-13 182, 1997.

    30 638, 639 Farman, J. C., Oneill, A., and Swinbank, R.: The dynamics of the arctic polar vortex during the EASOE campaign, Geophys. Res. Lett., 21, 1195-1198, 1994. 643 Flentje, H., Renger, W., and Wirth, M.: Validation of Contour Advection simulations with airborne lidar measurements of filaments during the Second European Stratospheric Arctic and Midlatitude Experiment (SESAME), J. Geophys. Res.-Atmos., 105, 15 417-15 437, 2000. 638, 654 G. Brasseur, J. O. and Tyndall, G.: Atmospheric Chemistry and Global Change, Oxford Univer-

  • Metrics
    No metrics available
Share - Bookmark