Classification of Stratosphere Winter Evolutions Into Four Different
Scenarios in the Northern Hemisphere: Part B Coupling With The Surface
Abstract
We have conducted an investigation into the coupling between the
stratosphere and troposphere, focusing on perturbed and unperturbed
scenarios of the northern hemisphere polar vortex. These scenarios were
established in a previous study, which categorized the main winter
typologies based on the timing of sudden stratospheric warmings (SSWs)
and final stratospheric warmings (FSWs). Here, we further analyze the
mass-weighted divergence of the Eliassen-Palm (EP) flux to confirm the
association between these scenarios and the specific timing of momentum
and heat flux deposition by planetary waves. Our analysis reveals that
wave-1 and wave-2 contributions to this divergence confirm distinct wave
activity effects in relation to these scenarios. Additionally, examining
the evolutions of the Northern Annular Mode (NAM) provides further
insight, demonstrating that these scenarios represent unique states of
both the stratosphere and troposphere, which mutually influence each
other during the winter months. Of particular interest is the
observation of descending stratospheric anomalies into the troposphere
following SSWs, often accompanied by a negative phase of the Arctic
Oscillation (AO). Notably, we have made an important discovery regarding
surface precursors for perturbed scenarios in early winter, specifically
December. These surface precursors display wave-like patterns that align
with the diagnosed wave activity in the upper stratosphere. This finding
establishes a connection between early and late winter, highlighting the
importance of these precursors. Consequently, our results enhance our
ability to anticipate the behavior of the polar vortex and its impacts,
thus holding significant implications for sub-seasonal to seasonal
forecasts in the northern hemisphere.