Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 3 2008 10.5194/acpd-8-9239-2008 http://www.atmos-chem-phys-discuss.net/8/9239/2008/ http://www.atmos-chem-phys-discuss.net/8/9239/2008/acpd-8-9239-2008.html http://www.atmos-chem-phys-discuss.net/8/9239/2008/acpd-8-9239-2008.pdf 9239 9261 2008-05-22 Simulation of the climate impact of Mt. Pinatubo eruption using ECHAM5 – Part 2: Sensitivity to the phase of the QBO M. A. Thomas manu.thomas@zmaw.de M. A. Giorgetta C. Timmreck H.-F. Graf G. Stenchikov Max-Planck Institute for Meteorology, Hamburg, Germany Center for Atmospheric Sciences, Cambridge University, UK Department of Environmental Sciences, Rutgers-The State University of NJ, USA The QBO (quasi-biennial oscillation) is a quasi-periodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere with a mean period of 28 to 29 months. In this paper, the sensitivity of the impact of Mt. Pinatubo eruption in the tropics and extratropics to different QBO phases is investigated. Mt. Pinatubo erupted in June 1991 during the easterly phase of the QBO at 30 hPa and the phase change to westerly took place in August 1992. Here, the consequences are analyzed if the eruption had taken place in the opposite QBO phase. Hence, in this study simulations are carried out for two cases – one with the observed QBO phase as discussed in part-I of this paper and the other with the opposite QBO phase. The QBO signature in the lower stratospheric temperature is well captured in the pure QBO responses and in the combined (aerosol+ocean+QBO) responses. Our results also show that a deepening of the polar vortex is not simulated during the first winters, but is seen during the second winters irrespective of the QBO phases in the pure QBO responses. However, a strong polar vortex is observed in the second winter when the QBO is in its westerly phase in the combined (aerosol+ocean+QBO) response in agreement with previous studies. Andrews, D. J., Holton, J. R., and Leovy, C. B.: Middle atmosphere dynamics, Academic Press, 489 pp., 1987. Baldwin, M. P., Gray, L. J., Dunkerton, T. J., Hamilton, K., Haynes, P. H., Randel, W. J., Holton, J. R., Alexander, M. J., Hiorta, I., Horinouchi, T., Jones, D. B. A., Kinnersley, J. S., Marquardt, C., Sato, K., and Takahashi, M.: The quasi-biennial oscillation, J. Geophys. Res., 104, 30 937–30 946, 2001. Bhalme, H. N., Rahalkar, S. S., and Sikdar, A. B.: Tropical quasi-biennial oscillation of the 10 mb wind and Indian monsoon rainfall-Implications for forecasting, J. Clim., 7, 345–353, 1987. Bruhwiler, L. and Hamilton, K.: A numerical simulation of the stratospheric ozone quasi biennial oscillation using a comprehensive general circulation model, J. Geophys. Res., 104, 30523–30557, 1999. Chattopadhyay, J. and Bhatla, R.: Possible influence of QBO on teleconnections relating Indian summer monsoon rainfall and sea-surface temperature anomalies across the equatorial pacific, Int. J. Climatology, 22, 121–127, 2002. Garfinkel, C. I. and Hartmann, D. L.: Effects of El Niño -Southern Oscillation and the Quasi-Biennial Oscillation on polar temperatures in the stratosphere, J. Geophys. Res., 112, D19112, doi:10.1029/2007JD008481, 2007. Giorgetta, M. and Bengtsson, L.: The potential role of the quasi-biennial oscillation in the stratosphere-troposphere exchange as found in water vapor in general circulation model experiments, J. Geophys. Res., 104, 6003–6019, 1999. Giorgetta, M., Bengtsson, L., and Arpe, K.: An investigation of QBO signals in the east Asian and Indian monsoon in GCM experiments, Clim. Dyn., 15, 435–450, 1999. Giorgetta, M., Manzini, E., and Roeckner, E.: Forcing of the quasi-biennial oscillation from a broad spectrum of atmospheric waves, Geophys. Res. Lett., 29, 86–90, 2002. Giorgetta, M., Manzini, E., Roeckner, E., Esch, M., and Bengtsson, L.: Climatology and forcing of the Quasi-Biennial Oscillation in the MAECHAM5 model, J. Clim., 19, 3882–3901, 2006. Graf, H.-F., Kirchner, I., Robock, A., and Schultz, I.: Pinatubo eruption winter climate effects: Model versus observations, Clim. Dyn., 9, 81–93, 1993. Hamilton, K.: Effects of an imposed quasi-biennial oscillation in a comprehensive troposphere-stratosphere-mesosphere general circulation model, J. Atmos. Sc., 55, 2393–2418, 1998. Holton, J. R. and Tan, H. -C.: The influence of the equatorial quasi-biennial oscillation on the global circulation at 50 mb, J. Atmos. Sci., 37, 2200–2208, 1980. Holton, J. R. and Tan, H. -C.: The quasi biennial oscillation in the Northern Hemisphere lower stratosphere, J. Meteo. Soc. Japan, 60, 140–148, 1982. Jaeger, H.: Long-term record of lidar observations of the stratospheric aerosol layer at Garmisch-Partenkirchen, J. Geophys. Res., D08106, doi:10.1029/2004JD005506, 2005. Kirchner, I. and Graf, H.-F.: Volcanoes and El Niño: Signal separation in Northern Hemisphere winter, Clim. Dynam., 11, 341–358, 1995. Labitzke, K. and Van Loon, H.: Association between the 11-year solar cycle, the QBO, and the atmosphere, Part I, The troposphere and the stratosphere in the Northern Hemisphere in winter, J. Atmos. Terr. Phys., 50, 197–207, 1988. Labitzke, K.: Sunspots, the QBO and the stratospheric temperature in the North Polar region, Geophys. Res. Lett., 14, 535–537, 1987. Manzini, E., Giorgetta, M. A., Esch, M., Kornblueh, L., and Roeckner, E.: The influence of sea surface temperatures on the northern winter stratosphere: Ensemble simulations with the MAECHAM5 model, J. Clim., 19, 3863–3881, 2006. Mukherjee, B. K., Indira, K., Reddy, R. S., and Ramana Murty, B. V.: Mon. Weather Rev., 113, 1421–1429, 1985. Robock, A. and Mao, J.: The volcanic signal in surface temperature observations, J. Clim., 8, 1086–1103, 1995. Stenchikov, G., Robock, A., Ramaswamy, V., Schwarzkopf, M. D., Hamilton, K., and Ramachandran, S.: Arctic Oscillation response to the 1991 Mount Pinatubo eruption: Effects of volcanic aerosols and ozone depletion, J. Geophys. Res., 107, 1–16, 2002. Stenchikov, G., Hamilton, K., Robock, A., Ramaswamy, V., and Schwarzkopf, M. D.: Arctic Oscillation response to the 1991 Pinatubo eruption in the SKYHI general circulation model with a realistic quasi-biennial oscillation, J. Geophys. Res., 109,\blackbox\bf please give the page numbers. 2004. Trepte, C. R. and Hitchman, M. H.: Tropical stratospheric circulation deduced from satellite aerosol data, Nature, 355, 626–628, 1992. Trepte, C. R., Veiga, R. E., and McCormick, M. P.: The poleward dispersal of Mount Pinatubo volcanic aerosol, J. Geophys. Res., 98, 18 5563–18 573, 1993. Yasunari, T.: A possible link of the QBOs between the stratosphere, troposphere and sea surface temperature in the tropics, J. Met. Soc. Japan, 67, 483–493, 1989.