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STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Seasonal and interannual variation of mesospheric waves at middle and high latitudes Hoffmann Peter , Becker Erich , Rapp Markus , Singer Werner , Bremer Jürgen , Placke Manja Leibniz Institute of Atmospheric Physics at the Rostock University, Kühlungsborn, Germany The seasonal and interannual variation of the wave activity in the mesosphere/lower thermosphere (MLT) at middle and high latitudes is presented on the basis of nearly identical wind measurements with meteor and MF radars at Juliusruh (55°N, 13°E) and Andenes (69°N, 16°E). The annual cycle of winds and waves at both latitudes is discussed with simulations using the mechanistic general circulation model KMCM which reproduces the main observed features very well. For the observations, proxies for the activity of mid-frequency gravity waves (GWs) and waves with longer periods are computed from their variances estimated as sum of wavelets for defined bandwidths. The corresponding proxy for the simulated GWs is the non-rotational kinetic energy due to the resolved mesoscales. Both observational and computational results show the strongest GW energy during winter and a secondary maximum during summer. This semi-annual variation is consistent with directional GW filtering by the annual cycle of the mean zonal wind. The latitudinal dependence during summer is characterized by stronger GW energy below about 82 km at middle latitudes than at polar latitudes, and a corresponding upward shift of the wind reversal towards the pole which is also reflected by the simulated GW drag. Mesospheric wind measurements are available at Juliusruh since 1990. First results of long term investigations at middle latitudes indicate a negative trend of the zonal winds below 80 km during summer. This increase of the observed westward directed winds during July goes along with an enhanced gravity wave activity at altitudes above 80 km. These results for middle latitudes will be compared with the data derived at Andenes since 1999.
STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Comparison of Observed 11-Year Signals in Stratospheric Ozone and Temperature with CCM Simulations Including a Coupled Ocean and Troposphere Hood Lon L. 1 , Matthes Katja 2 , Soukharev Boris E. 1 , Arblaster Julie M. 3 , Sassi Fabrizio 4 , Meehl Gerald A. 5 1 Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85721, USA, 2 Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences, Potsdam, Germany, 3 Center for Australian Weather and Climate, Bureau of Meteorology, Melbourne, Australia, 4 Naval Research Laboratory, Washington, DC 20375, USA, 5 National Center for Atmospheric Research, P.O. Box 3000, Boulder, Colorado 80307, USA Observational studies of stratospheric ozone and temperature records since the onset of continuous global satellite measurements (1979) indicate the existence of responses to 11-year solar UV forcing at tropical and subtropical latitudes. In addition to an upper stratospheric response that is attributable to direct photochemical and radiative forcing, a significant variation is also observed in the lower stratosphere that appears to be dynamical in origin and is much less well understood. The latter variation has not yet been fully simulated by chemistry climate models that consider only stratospheric processes with fixed sea surface temperatures. Observational studies have also identified 11-year surface climate signals in the tropical Pacific that resemble those observed during cold ENSO events (van Loon et al., JGR, 2007). The latter signals have recently been approximately simulated using the WACCM model coupled to the ocean, land, and sea ice components of an ocean-troposphere model (CCSM3) (Meehl et al., Science, 2009). Here, we report an initial comparison of the latter coupled WACCM/CCSM3 model output for stratospheric ozone and temperature (with and without a modeled QBO) to observed 11-year responses derived using a multiple regression statistical model. The purpose of the comparison is to better determine the origin of the tropical lower stratospheric response, especially whether the response may be amplified by feedbacks from the ocean-troposphere response. The statistical model includes a lagged ENSO term and two lagged QBO terms to minimize any aliasing of the solar regression coefficients by internal sources of stratospheric interannual variability. A number of qualitative agreements are found. For example, the observed geographical dependence of the total column ozone response in NH winter (characterized by low values in the equatorial eastern Pacific and higher values in the subtropical eastern Pacific) is similar to that obtained from the model ozone data. A more detailed comparison of the observed and modeled tropical ozone and temperature responses and their dependences on season, altitude, latitude, and longitude (with and without including a QBO in the WACCM model) will be presented.
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scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

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