Regime Behavior in the Upper Stratosphere as a Precursor of Stratosphere-Troposphere Coupling in the Northern Winter
نویسندگان
چکیده
Abstract A new regime index is constructed to capture the seasonal development of stratospheric polar vortex in northern winter, based on standard deviation Ertel’s potential vorticity upper stratosphere November-December. The narrow-jet flow characterized by a that more confined high latitudes early winter stratosphere. This upper-level configuration susceptible disturbances upward propagating planetary-scale Rossby waves; thus weakens earlier and vertically shallower. wide-jet broader-than-average extends further into subtropics early-winter night jet then gradually strengthens, moves poleward penetrates deep lowermost stratosphere, with sharply-defined edge accompanied due frequent wave breaking. Composite differences analyses show wide narrow regimes, defined uppermost November-December, lead different circulation anomalies lower-stratosphere troposphere January-February, offering for improved predictability sub-seasonal forecasts up two months ahead. lower tropospheric responses January-February are zonally asymmetric. projects most strongly over North Atlantic, an equatorward-shifted, and/or broader mid-latitude westerly jet. wide-jet-regime response weakened Pacific. regimes also differ their impacts storm track Western Europe east coast America, which may have implications extreme weather events those regions.
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ژورنال
عنوان ژورنال: Journal of Climate
سال: 2021
ISSN: ['1520-0442', '0894-8755']
DOI: https://doi.org/10.1175/jcli-d-20-0831.1