scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Modulation of the 'stratospheric bridge' by the Pacific Decadal Oscillation, Quasi-
Biennial Oscillation and the 11-year solar cycle
Jadin Evgeny 1 , Wei Ke 2 , Chen Wen 2 , Wang Lin 2
1 P.P.Shirshov Institute of Oceanology, 2 Institute of Atmospheric Physics, Beijing
Analysisof the monthly mean three-dimensional Eliassen-Palm fluxes indicated the
existence of the “stratospheric bridge” forming by the upward planetary wave propagation
from the troposphere over northern Eurasia in early winter and the downward wave signal
from the stratosphere over North Atlantic in late winter (January-February). In early winter
(December), the interannual changes of the planetary wave activity control partly the
variations of the stratospheric circulation in subsequent January. The interannual and decadal
variations of the upward wave flux in December are strongly associated with the sea surface
temperature (SST) anomalies in the North Pacific (Pacific Decadal Oscillation - PDO) in early
winter during 1958-1979 and 1992-2007. A decadal period from the mid- 1970s to mid-
1990s of the Holton-Tan (HT) relationship violation corresponds well to that of the positive
PDO phase (anomalously cold SSTs in the central North Pacific). The absence of the
modulation of the stratospheric circulation by the 11-year solar cycle in early winter can be
connected with this oceanic forcing on the thermal excitation of the stationary planetary
waves.
In contrast with early winter, the large role in the wave-zonal flow interaction plays the
downward wave flux from the stratosphere to the troposphere over Canada and North Atlantic
in January-February. The sink of the eddy energy from the stratosphere occurs in this
“stratospheric wave hole” region. One can suggest that there are two dominant regimes in the
stratosphere-troposphere coupling in late winter: 1) the “ventilation regime” with the strong
penetration of planetary waves from the troposphere over north Eurasia and their strong
downward propagation over Canada and North Atlantic, and 2) the “blocking regime” with
the weak those.
It is shown that the decadal HT relationship violation from the mid- 1970s to mid- 1990s
is associated with an exchange of these regimes for the west/east QBO years in late winter.
This simple physical mechanism can also explain why the stratospheric warmings are
observed more often for the west QBO (wQBO) years during high solar activity (HS/wQBO)
and east QBO (eQBO) years during low solar activity (LS/eQBO) than for LS/wQBO and
HS/eQBO years.