HR: 11:30h
AN: A12A-05    [Abstracts]
TI: Wave driven quasi-biennial and annual equatorial oscillations in the zonal circulation as potential amplifiers of UV solar cycle influence on the lower atmosphere
AU: * Mayr, H G
EM: hmayr@pop900.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Greenbelt Rd., Greenbelt, MD 20771 United States
AU: Mengel, J G
EM: jmengel@pop900.gsfc.nasa.gov
AF: Science Systems & Applications, Inc., 10210 Greenbelt Rd., Lanham, MD 20706 United States
AU: Porter, H S
EM: Hayden.Porter@furman.edu
AF: Furman University, 3300 Poinsett Highway, Greenville, SC 29613 United States
AB: We discuss a 3D global modeling study that describes the gravity wave (GW) driven quasi-biennial and annual equatorial oscillations under the influence of solar cycle (SC) UV variations. For a SC period of 10 years, the amplitude of the variations of radiative forcing is taken to vary from 0.2% at the surface to 2% at 50 km to 20% at 100 km and above. Applying spectral analysis to filter out and identify the SC signatures, this model produces two distinct dynamical phenomena. (1) A relatively large modulation is generated in the Quasi-biennial Oscillation (QBO) of the lower stratospheric zonal circulation, which is in qualitative agreement with the results obtained by Salby and Callaghan (2000) who analyzed zonal wind observations covering more than 40 years. The modeled SC modulation of the QBO extends to high latitudes where it produces temperature variations of < 1 K in the troposphere. (2) Modulated by the SC, a hemispherically symmetric Annual Oscillation (AO) is generated in the zonal winds, which is largely confined to low latitudes. Under the influence of the GWs, this AO propagates down into the lower stratosphere like the QBO. As is the case for the QBO, the energy of this tropical AO is partially redistributed by the meridional circulation and planetary waves, presumably, to generate measurable SC signatures in the tropospheric temperature of the polar regions, which may be related to the so called Arctic Oscillation (Thompson and Wallace, 1998). Because of the symmetry of this AO, and the QBO, the resulting SC signatures in the northern and southern hemispheres are significantly different. We tentatively conclude that the wave mean flow interactions at equatorial latitudes appear to pull down, through the QBO and "symmetric" AO, the UV solar cycle influence of the middle atmosphere and thereby amplify effectively the SC effect at lower altitudes.
DE: 1650 Solar variability
DE: 3309 Climatology (1620)
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3362 Stratosphere/troposphere interactions
DE: 3367 Theoretical modeling
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly