Possible Associations between the Number of Cold Days over East Asia and Arctic Oscillation and Arctic Warming

Wei Song,Xiaochen Ye

doi:10.3390/atmos12070842

Wei Song, Xiaochen Ye

Open Access

https://doi.org/10.3390/atmos12070842

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Abstract

Based on the NECP/NCAR reanalysis dataset, the associations between the number of cold days (NCD) over East Asia (100–150° E, 25–55° N) and Arctic Oscillation (AO)/Arctic warming during 1956–2015 are explored. The results show the NCD was closely associated with AO during 1956–1990 and Arctic warming during 1991–2015. It reveals NCD over East Asia showed a downward trend and a significantly negative correlation with AO in the previous stage, while it presented an upward trend and notably positive association with Arctic warming in the later period. Meanwhile the increase in the earlier-stage AO will often be accompanied by the weakness of the Siberian high (SH), the Ural Mountains Blocking high (UBH), and the East Asian trough (EAT), and a “positive–negative–positive” wave band exist in the upper troposphere, which is linked with weakened northerly wind over East Asia. All these anomalies are unfavorable for the southward transportation of cold air, eventually leading to the decrease in NCD over East Asia. Additionally, when the near-surface temperature over the Arctic rises in the later period, on the one hand, SH reinforces and further results in more NCD over East Asia; on the other hand, the 1000–500 hPa thickness field displays a “north positive–south negative” pattern, which is conducive to the deceleration of the westerlies at mid-latitudes over Eurasia, and further bring about the enhancement of EAT and UBH, favoring the southward intrusion of cold air, finally, more NCD are generated.

Highlights

When the zonal wind over Eurasia decelerated, the positive Z500 anomalies were observed from the Barents–Kara Sea to the Baikal Lake, and negative Z500 anomalies prevailed in East Asia (Figure not shown) implying the reinforcement of Ural Mountains Blocking high (UBH) and East Asian trough (EAT)
We preliminarily inquired into the variations of number of cold days (NCD) over East Asia, and its possible relationships with Arctic Oscillation (AO) and Arctic warming were further discussed
High-latitudes over Eurasia, and the variations of the above systems were conducive to the intrusion of cold air into East Asia

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Cold surges are the most profound climate feature in boreal winter impacting East Asian countries, such as China, Japan, and Korea [1], and variability of winter temperature over East Asia and its causes have been investigated extensively [2,3,4,5,6]. In the last two decades, accompanied by global warming and Arctic Sea ice loss, the ecological environment over the Arctic has been changing rapidly, and the Arctic amplification effect has become more prominent [16], strengthening the connection between the Arctic and the mid–low-latitudes, and increasing intraseasonal and interannual variability of atmospheric circulations [17,18,19]; simultaneously, the instability of winter temperature over East Asia has increased and extreme cold events have become more frequent and intensive [7].

Data and Method

Findings

11. The longitude-height cross-section correlationeffect coefficients

Summary and Discussions