Details

Autor(en) / Beteiligte

• Xu, Xinping
• He, Shengping
• Zhou, Botao
• Wang, Huijun
• Outten, Stephen

Titel

The Role of Mid‐latitude Westerly Jet in the Impacts of November Ural Blocking on Early‐Winter Warmer Arctic‐Colder Eurasia Pattern

Ist Teil von

• Geophysical research letters, 2022-08, Vol.49 (16), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2022

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Based on statistical analysis using observations and idealized model simulations, previous studies have revealed the potential response of early‐winter atmospheric circulation and temperature anomalies to November Ural blocking (UB) anomalies. Using a large number of coupled simulations, this study found that the response is sensitive to the intensity of November mid‐latitude westerly jet over Eurasia. Stronger‐than‐normal November UB without a significantly weakened westerly jet could not cause significant atmospheric response in early‐winter. By contrast, stronger‐than‐normal November UB with a significantly weakened jet would be followed by a warmer Arctic‐colder Eurasia (WACE) pattern in December. The significantly weakened westerly jet favors stronger upward propagation of planetary waves, which causes stronger weakening and longer persistence of the stratospheric polar vortex. This stratospheric response persists into December and propagates downward into the troposphere interfering with planetary waves (especially wavenumber‐1). The lead‐lag UB‐WACE linkage modulated by mid‐latitude jet may have implications for sub‐seasonal predictability. Plain Language Summary Observations and idealized model simulations have shown that strong Ural blocking (UB) anomalies in November can induce the “warmer Arctic, colder Eurasia” anomaly in the following December. In this study, a large number of coupled simulations are employed. The results show that the impact of November UB on early‐winter Arctic‐Eurasian temperature is sensitive to the intensity of November mid‐latitude (around 60°N) westerly jet over Eurasia. When November UB anomalies are accompanied by a significantly weakened mid‐latitude westerly jet, early‐winter would experience a warmer Arctic‐colder Eurasia pattern. The significantly weakened westerly wind waveguide is favorable for stronger upward propagation of planetary waves caused by UB anomalies, which leads to persistent atmospheric response in the following December. Key Points Early‐winter atmospheric response to November Ural blocking (UB) anomalies is sensitive to the background state of westerly jet Strong UB with sufficiently weakened westerly jet in November can induce a warmer Arctic‐colder Eurasia pattern in December The weakened westerly wind waveguide promotes stronger upward propagation of planetary waves forced by UB anomalies