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Modulation of Ural blocking and Eurasian winter climate by the quasi-biennial oscillation
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DOI：10.1007/s00382-026-08346-2.png)
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Abstract
En 中文
Ural blocking is a major driver of Eurasian winter climate variability, but its modulation by equatorial stratospheric variability remains poorly understood. Using NCEP/NCAR reanalysis data from 1960 to 2023, we show that the quasi-biennial oscillation (QBO) significantly alters the structure, vertical extent, and persistence of Ural blocking via wave–mean flow interactions. During the westerly QBO (WQBO), Ural blocking anomalies are more zonally elongated and confined to the troposphere, favoring strong easterly flow that advects cold air westward into Central Asia and Europe. In contrast, during the easterly QBO (EQBO), Ural blocking becomes more meridionally oriented and vertically extended, steering cold anomalies southwestward from Central Asia toward the Middle East and the Mediterranean. These distinct responses arise because the WQBO enhances poleward but weakens upward planetary wave propagation, whereas the EQBO produces the opposite response. Accordingly, the WQBO is associated with a strengthened subtropical jet and weaker stratosphere–troposphere coupling, whereas the EQBO induces a weakened subtropical jet and stronger coupling. Furthermore, the WQBO is characterized by stronger Eliassen–Palm (EP) flux divergence in the lower-to-middle troposphere and stronger EP flux convergence in the upper troposphere than the EQBO. This vertical EP-flux structure is less favorable for maintaining Ural blocking, contributing to its shorter duration and less widespread surface cooling during the WQBO. Our results have important implications for improving subseasonal-to-seasonal predictions of Eurasian winter climate.
Keywords:
Ural blocking
Quasi-biennial oscillation (QBO)
Eurasian winter climate
Planetary wave propagation
Stratosphere–troposphere coupling
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