Mathematics – Logic
Scientific paper
Feb 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009georl..3603819s&link_type=abstract
Geophysical Research Letters, Volume 36, Issue 3, CiteID L03819
Mathematics
Logic
4
Atmospheric Processes: Middle Atmosphere Dynamics (0341, 0342), Atmospheric Processes: Stratosphere/Troposphere Interactions, Atmospheric Processes: General Circulation (1223)
Scientific paper
The stratospheric final warming is the final transition of the zonal winds from wintertime westerlies to summertime easterlies as solar heating of the high latitude stratosphere increases. Here the stratospheric influence on the tropospheric circulation during the stratospheric final warming events is investigated through ensemble model integrations of a simple dynamical core general circulation model. When the radiative equilibrium temperature in the stratosphere alone is gradually changed from a winter to a summer profile, the model generates realistic final warmings. As in the observations, the simulated final warmings occur at different ``dates'' in different realizations. Following previously published analyses of observed final warmings, we form a climatological springtime transition and compute composite anomalies centered on the final warmings. Simulations for both non-topographic and topographic cases show that starting five days before the final warming, the stratospheric zonal wind rapidly decelerates, in association with a strong upward Eliassen-Palm (EP) flux anomaly and EP flux convergence. Precursor events of wave driven zonal-wind deceleration occur, but at different times in simulations with and without topography. The composite zonal wind anomalies for final warmings with and without topography are compared with each other and with observations. In both cases, a statistically significant zonal wind anomaly extends downward to the surface, similarly to what is observed in the Northern Hemisphere (NH). These tropospheric zonal wind anomalies are stronger in the simulations with topography. Tropospheric geopotential height anomalies across the final warming also resemble NH observations.
Robinson Walter A.
Sun Lantao
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