Advances in Radio Science www.adv-radio-sci.net 1684-9965 1684-9973 6 Kleinheubacher Berichte 2007 2008 10.5194/ars-6-331-2008 http://www.adv-radio-sci.net/6/331/2008/ http://www.adv-radio-sci.net/6/331/2008/ars-6-331-2008.html http://www.adv-radio-sci.net/6/331/2008/ars-6-331-2008.pdf 331 335 2008-07-21 Low-frequency lower E-region wind and reflection height measurements as sensor for climate variability C. Jacobi jacobi@uni-leipzig.de Institute for Meteorology, University of Leipzig, Stephanstr. 3, 04103 Leipzig, Germany Measurements of reflection heights of low-frequency (LF) radio waves at oblique incidence and estimates of mesosphere/lower thermosphere (MLT) region horizontal winds applying the D1 spaced receiver method on LF field strength registrations are analyzed with respect to possible long-term trends and interdecadal variability in the time interval from ~1980 to date. While no clear signal of mesospheric height trend is registered during the last two decades, significant trends of MLT horizontal winds are found. These trends are non-linear, in particular a change of trends around 1990 is found, which is probably connected with changes in tropospheric and stratospheric conditions at that time. Beig, G.: Trends in the mesopause region temperature and our present understanding – an update, Phys. Chem. Earth, 31, 3–9, 2006. Beig, G., Keckhut, P., Lowe, R. P., Roble, R. G., Mlynczak, M. G., Scheer, J., Fomichev, V. I., Offermann, D., French, W .J. R., Shepherd, M. G., Semenov, A. I., Remsberg, E. E., She, C. Y., Lübken, F.-J., Bremer, J., Clemesha, B. R., Stegman, J., Sigernes, F., and Fadnavis, S.: Review of mesospheric temperature trends, Rev. Geophys., 41, 1015, doi:10.1029/2002RG000121, 2003. Bremer, J. and Berger, U.: Mesospheric temperature trends derived from ground-based LF phase-height observations at mid-latitudes: comparison with model simulations, J. Atmos. Solar-Terr. Phys., 64, 805–816, 2002. Bremer, J., Schacht, J., and Barth, Th.: Einfluss von Ozonvariationen auf Trends in der Mesosphäre mittlerer Breiten. Leibnitz-Institut für Atmosphärenphysik e.V. an der Universität Rostock, Institute Report 2004/2005, 94–95, 2005. Jacobi, Ch., Schminder, R., and Kürschner, D.: Planetary wave activity obtained from long-term (2-18 days) variations of mesopause region winds over Central Europe (52° N, 15° E), J. Atmos. Solar-Terr. Phys., 60, 81–93, 1998. Jacobi, Ch. and Beckmann, B.-R.: On the connection between upper atmospheric dynamics and tropospheric parameters: correlation between mesopause region winds and the North Atlantic Oscillation, Clim. Change, 43, 629–643, 1999. Jacobi, Ch., Lange, M., and Kürschner, D.: Influence of anthropogenic climate gas changes on the summer mesospheric/lower thermospheric meridional wind, Meteorol. Z., N.F. 12, 37–42, 2003. Jacobi, Ch. and Kürschner, D.: Long-term trends of MLT region winds over Central Europe, Phys. Chem. Earth, 31, 16–21, 2006. Kürschner D.: Ein Beitrag zur statistischen Analyse hochatmosphärischer Winddaten aus bodengebundenen Messungen, Z. Meteorol., 41, 262–266, 1991. Kürschner, D., Schminder, R., Singer, W., and Bremer, J.: Ein neues Verfahren zur Realisierung absoluter Reflexionshöhenmessungen an Raumwellen amplitudenmodulierter Rundfunksender bei Schrägeinfall im Langwellenbereich als Hilfsmittel zur Ableitung von Windprofilen in der oberen Mesopausenregion, Z. Meteorol., 37, 322–332, 1987. Kürschner, D. and Jacobi, Ch.: Quasi-biennial and decadal variability obtained from long-term measurements of nighttime radio wave reflection heights over central Europe, Adv. Space Res., 32, 1701–1706, doi:10.1016/S0273-1177(03)00773-2, 2003. Lastovicka, J., Akmaev, R. A., Beig, G., Bremer, J., and Emmert, J. T.: Global change in the upper atmosphere, Science, 314, 1253–1254, 2006. Portnyagin, Yu. I., Merzlyakov, E. G., Solovjova, T. V., Jacobi, Ch., Kürschner, D., Manson, A., and Meek, C.: Long-term trends and year-to-year variability of mid-latitude mesosphere/lower thermosphere winds, J. Atmos. Solar-Terr. Phys., 68, 1890–1901, 2006. Ramaswamy, V., Chanin, M.-L. , Angell, J., Barnett, J., Gaffen, D., Gelman, M., Keckhut, P., Koshelkov, Y., Labitzke, K. , Lin, J.-J.R., O'Neill, A., Nash, J., Randel, W., Rood, R., Shine, K., Shiotani, M., and Swinbank, R.: Stratospheric temperature trends: Observations and model simulations, Rev. Geophys., 39, 71–122, 2001. Remsberg, E. E. and Deaver, L. E.: Interannual, solar cycle, and trend terms in middle atmospheric temperature time series from HALOE, J. Geophys. Res., 110, D06106, doi:10.1029/2004JD004905, 2005.