Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 6 12 2006 10.5194/acp-6-5391-2006 http://www.atmos-chem-phys.net/6/5391/2006/ http://www.atmos-chem-phys.net/6/5391/2006/acp-6-5391-2006.html http://www.atmos-chem-phys.net/6/5391/2006/acp-6-5391-2006.pdf 5391 5397 2006-12-04 Accuracy of analyzed temperatures, winds and trajectories in the Southern Hemisphere tropical and midlatitude stratosphere as compared to long-duration balloon flights B. M. Knudsen bk@dmi.dk T. Christensen A. Hertzog A. Deme F. Vial J.-P. Pommereau Danish Meteorological Institute, Copenhagen, Denmark Laboratoire de Météorologie Dynamique du Centre National de la Recherche Scientifique, France Service d'Aeronomie du Centre National de la Recherche Scientifique, France Eight super-pressure balloons floating at constant level between 50 and 80 hPa and three Infra-Red Montgolfier balloons of variable altitude (15 hPa daytime, 40–80 hPa night time) have been launched at 22° S from Brazil in February–May 2004 in the frame of the HIBISCUS project. The flights lasted for 7 to 79 days residing mainly in the tropics, but some of them passed the tropical barrier and went to southern midlatitudes. Compared to the balloon measurements just above the tropical tropopause the ECMWF operational temperatures show a systematic cold bias of 0.9 K and the easterly zonal winds are too strong by 0.7 m/s. This bias in the zonal wind adds to the ECMWF trajectory errors, but they still are relatively small with e.g. about an error of 700 km after 5 days. The NCEP/NCAR reanalysis trajectory errors are substantially larger (1300 km after 5 days). In the southern midlatitudes the cold bias is the same, but the zonal wind bias is almost zero. The trajectories are generally more accurate than in the tropics, but for one balloon a lot of the calculated trajectories end up on the wrong side of the tropical barrier and this leads to large trajectory errors. Gobiet, A., Foelsche, U., Steiner, A. K., Borsche, M., Kirchengast, G., and Wickert, J.: Climatological validation of stratospheric temperatures in ECMWF operational analyses with CHAMP radio occultation data, Geophys. Res. Lett., 32, L12806, doi:10.1029/2005GL022617, 2005. Hertzog, A., Basdevant, C., Vial, F., and Mechoso, C. R.: Some results on the accuracy of stratospheric analyses in the Northern Hemisphere inferred from long-duration balloon flights, Quart. J. Roy. Meteorol. Soc., 129, 607–626, 2004. Kalnay, E., Kanamitsu, M., Kistler, R., et al.: The NCEP/NCAR 40-year reanalysis project, Bull. Am. Meteorol. Soc., 77, 437–471, 1996. Kistler, R., Kalnay, E., Collins, W., et al.: The NCEP-NCAR 50-year reanalysis: Monthly means CD-ROM and documentation, Bull. Am. Meteorol. Soc., 82, 247–267, 2000. Knudsen, B. M., Pommereau, J.-P., Garnier, A., Nunez-Pinharanda, M., Denis, L., Letrenne, G., Durand, M., and Rosen, J. M.: Comparison of stratopheric air parcel trajectories based on different meteorological analyses, J. Geophys. Res., 106, 3415–3424, 2001. Knudsen, B. M. and Carver, G. D.: Accuracy of the isentropic trajectories calculated for the EASOE campaign, Geophys. Res. Lett., 21, 1199, 1994. Pommereau, J.-P. and Hauchecorne, A.: A new atmospheric vehicle: la Mongolfière infrarouge, Adv. Space Res., 55, 1979. Rabier, F., Järvinen, H., Klinker, E., Mahfouf, J.-F., and Simmons, A.: The ECMWF operational implementation of four dimensional variation assimilation. I: Experimental results with simplified physics, Quart. J. Roy. Meteorol. Soc., 126, 1143–1170, 2000. Randel, W. J., Wu,~F., Oltmans,~S. J., Rosenlof,~K., and Nedoluha,~G. E.: Interannual Changes of Stratospheric Water Vapor and Correlations with Tropical Tropopause Temperatures, J. Atmos. Sci., 61, 2133–2148, 2004b. Randel, W., Udelhofen, P., Fleming, E., Geller, M., Gelman, M., Hamilton, K., Karoly, D., Ortland, D., Pawson, S., Swinbank, R., Wu, F., Baldwin, M., Chanin, M.-L., Keckhut, P., Labitzke, K., Remsberg, E., Simmons, A., and Wu, D.: The SPARC Intercomparison of Middle-Atmosphere Climatologies, J. Climate, 17, 986–1003, 2004a. Simmons, A.: Representation of the stratosphere in ECMWF operations and ERA-40, Workshop on modelling and assimilation for the stratosphere and troposphere, Reading, 23–26 June, 2003. Simmons, A. J., Untch, A., Jacob, C., Kållberg, P., and Undén, P.: Stratospheric water vapour and tropical tropopause temperatures in ECMWF analyses and multi-year simulations, Quart. J. Roy. Meteorol. Soc., 125, 353–386, 1999. SPARC: Intercomparison of Middle Atmosphere Climatologies, SPARC Rep. 3, 96 pp., 2002. Vial, F., Hertzog, A., Mechoso, C. R., Basdevant, C., Cocquerez, P., Doubough, V., and Nouel, F.: A study of the dynamics of the equatorial lower stratosphere by the use of ultra long duration balloons. Part I: Planetary scales, J. Geophys. Res., 106, 22 725–22 744, 2001.