Winter Persistent Extreme Cold Events in Xinjiang Region and Their Associations with the Quasi-Biweekly Oscillation of the Polar Front Jet

Jie Jiang,Suxiang Yao

doi:10.3390/atmos12050597

Abstract

Winter persistent extreme cold events (WPECEs) often cause great damage to the development of economies and people’s lives. The sub-seasonal variation of the atmospheric circulation is regarded as one of important causes of extreme weather, and is key to propel the extended period prediction. In this paper, we mainly analyze the WPECEs in Xinjiang region and their relationship with the sub-seasonal variation of the East Asian polar front jet (PFJ). The results suggest the persistent extreme cold event (equal or greater than 7 days) occurs most frequently in Xinhe County of Xinjiang region, with obvious inter-annual and inter-decadal variations. Further analysis shows that the variation of the mean temperature in the key area has characteristics of intra-seasonal variation when the WPECE occurs. The result of composite analysis shows that this intra-seasonal variation is related to the sub-seasonal variation of atmospheric circulation, especially the PFJ anomalous activity near Lake Balkhash. By using the power spectrum analysis method, note that the PFJ activity has the characteristics of quasi-biweekly oscillation (QBWO) in WPECEs. On quasi-biweekly scale (10–20-day filtered), the weakening of PFJ, the intensification of the zonal easterly wind in the upper troposphere, the accumulation of the strong cold air, and the intensification of the meridional northerly wind in the lower troposphere enhance the occurrence of WPECEs in Xinjiang. Further investigation indicates that the quasi-biweekly PFJ mainly propagates eastward and southward before the WPECE occurs in Xinjiang, China.

Highlights

IPCC AR5 indicates that each of the last three decades has been successively warmer at the earth’s surface than any preceding decade since 1850, and warming of the climate system is unequivocal
If the daily average temperature of a station is lower than the extreme low temperature threshold for 7 consecutive days or more, it is considered that this single station winter persistent extreme cold event (WPECE) occurs
The results show that there are very significant inter-annual and inter-decadal differences in WPECE frequency in Xinjiang region, which are closely related to the quasi-biweekly oscillation (QBWO)

Summary

Introduction

IPCC AR5 indicates that each of the last three decades has been successively warmer at the earth’s surface than any preceding decade since 1850, and warming of the climate system is unequivocal. Under the RCP8.5 scenario, the extreme weather and climate events will very likely become more intense and frequent by the end of this century, as global mean surface temperature increases [1]. Extreme low temperature has an important effect on social environment and human life. China has suffered frequent persistent extreme cold events in winter. The long durations, wide ranges of influence, and cold-precipitation-freezing disasters [2,3,4] have a great influence on health, agricultural production, social lives, and other aspects of people’s lives [5,6,7,8].

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Conclusion