Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmsa62a0381m&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #SA62A-0381
Physics
3332 Mesospheric Dynamics, 3334 Middle Atmosphere Dynamics (0341, 0342), 3362 Stratosphere/Troposphere Interactions, 3367 Theoretical Modeling, 3384 Waves And Tides
Scientific paper
Our Numerical Spectral Model (NSM) extends from the ground up into the thermosphere and has a vertical grid point resolution of about 0.5 km to resolve the interactions of gravity waves (GWs) described with Hines' Doppler Spread Parameterization (DSP). This model produces in the stratosphere and mesosphere the major features of QBO, SAO, tides, and planetary waves. We discuss here results from an initial study with our 3D model that shows how certain tropospheric processes can affect the dynamics of the middle atmosphere. Under the influence of tropospheric heating and eddy viscosity, and augmented by GW interaction, two distinct but related processes can be identified. (1) A meridional circulation develops, which extends into the lower stratosphere with rising motions at low latitudes that are in magnitude comparable to the downward propagation of the QBO. As Dunkerton pointed out, a larger GW source is then required to reproduce the observed QBO, which tends to move us closer to the values recommended for the DSP. This has significant consequences for our ability to model the upper mesosphere, considering the central importance of GWs for the seasonal variations, planetary waves (e.g., 2-day wave) and tides in this region. (2) Tropospheric heating produces zonal jets near the tropopause that are related to latitudinal variations in pressure and reversing temperature (resembling the dynamical conditions near the mesopause), which in turn is conducive to generate baroclinic instability. Modeling results show that our ability to generate the QBO then critically depends on the magnitude of the temperature reversal that is a measure of this instability. Planetary waves are generated in this process, which can apparently interfere with or augment the GW interactions. Eastward propagating Kelvin waves and westward propagating Rossby gravity waves (generated by tropospheric convection) can generate the QBO in principle (Lindzen and Holton, 1968) and certainly influence it, and this process is reproduced with our 3D model.
Drob Douglas P.
Mayr Hans G.
Mengel John G.
Porter Hayden S.
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