Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmos12d..07g&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #OS12D-07
Physics
1620 Climate Dynamics (3309), 3319 General Circulation, 3339 Ocean/Atmosphere Interactions (0312, 4504), 3362 Stratosphere/Troposphere Interactions
Scientific paper
The connection of global sea surface temperatures with atmospheric circulation in boreal winter is studied based on correlation/regression analysis. We used observed monthly data at the surface of nearly 100 years as well as 3-dimensional atmospheric data reaching to the middle atmosphere (NCEP reanalysis) for at least 40 years. The results show that the correlation pattern of SST with the North Atlantic Oscillation is not stable on a multi decadal time scale. At the beginning and at the end of the 20th century NAO is correlated with the known tripole pattern of North Atlantic SST, but in the middle of the 20th century this correlation nearly vanishes. During times when the NAO-SST correlation in the North Atlantic is strong, NAO is characterized by strong decadal variability. . Analysis of the atmospheric EP flux divergence (which is driving the zonal winds) of stationary planetary waves reveals that tropical SST clearly is connected to an oscillation of upper stratospheric EP flux divergence in polar latitudes, and midlatitude SST (both of the North Pacific and Atlantic) is correlated with an oscillation of tropospheric EP flux divergence. The latter involves the region of the subtropical and the subpolar jets in the troposphere as well as of the lower stratospheric polar vortex. Tropospheric and stratospheric indices of the oscillation of EP flux divergence are statistically independent. It is supposed that both effects act permanently, but in times when the ocean may come into resonance with atmospheric decadal variability, the midlatitude SST-tropospheric circulation mode dominates. This mode is driven by the interaction of SST with synoptic waves, which lead to the formation and stability of stationary planetary waves. This process leads to an equivalent barotropic vertical wind structure reaching from the surface to the middle stratosphere. The tropical SST-upper stratospheric circulation mode is driven by the influence of deep tropical convection on the stratospheric residual circulation. It is weaker than the tropospheric mode in the last decades of the 20th century.
Chen Wei
Graf H.
Walter Katrin
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