Classification of Stratosphere Winter Evolutions Into Four Different Scenarios in the Northern Hemisphere: Part B Coupling With The Surface

• Main Authors: Mariaccia, Alexis, Keckhut, Philippe, Hauchecorne, Alain
• Format: Other/Unknown Material
• Language: unknown
• Published: Authorea, Inc. 2023
• Subjects: Arctic
• Online Access: http://dx.doi.org/10.22541/essoar.168677219.93346533/v1

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.