doi:  10.3878/j.issn.1006-9895.1710.17119

Circulation Characteristics of Extreme Cold Events in Northeast China during Wintertime
摘要点击 916  全文点击 248  投稿时间:2017-02-06  修订日期:2017-08-15
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中文关键词:  极端低温事件,中国东北,冬季,罗斯贝波,谐波分析
英文关键词:  Extreme cold events, Northeast China, Winter, Rossby wave, Harmonic analysis
李尚锋Li Shang Feng中国科学院大气物理研究所
姜大膀Jiang Da Bang中国科学院大气物理研究所
Citation:Li Shang Feng,Jiang Da Bang.2018.Circulation Characteristics of Extreme Cold Events in Northeast China during Wintertime[J].Chinese Journal of Atmospheric Sciences (in Chinese)
      利用1961~2014年CN05.2逐日温度数据,对冬季东北极端低温事件进行了定义,并按其发生时冷空气对中国东部(105°E以东)的影响范围,将其分为第一类和第二类极端低温事件,其中前者局限在东北,而后者则扩展至中国东部大部分地区。分析表明,在年代际时间尺度上,第一类极端低温事件强度减弱,而第二类的则增加;对持续天数而言,第二类极端低温事件的在减少,而第一类在1990s以前也持续减少,但是1990s之后急剧增加;2月份总的极端低温事件发生天数最多,其在1990s以前要远大于12月和1月份,且在1990s以前总体在减少,以后则增加;850 hPa风场分析显示,第二类极端低温事件中来自贝加尔湖的西北路径冷空气比第一类的要强,而来自鄂霍次克海的东北路径冷空气则相反;在E-P通量散度场上,这两类极端低温事件中东北都处于波动能量辐散中心,第二类极端低温事件发生时罗斯贝波波动能量传播比第一类时的要弱,第一类发生时则纬向传播比较明显,而且波动中心值都比较大;在位势高度距平场的谐波分析中,长波槽同位相扰动叠加在超长波槽上更易导致极端低温事件的发生。
      Using the daily mean temperature dataset of CN05.2 from 1961 to 2014, total extreme cold events (TECEs) are defined in this study and are divided into two categories according to the domain (east of 105°E in China ) they effected, namely, the first kind of extreme cold events (FKECEs) affecting only Northeast China and the second kind of extreme cold events (SKECEs) affecting most of eastern China. Results show that the trend of FKECEs’ intensity is significantly negative, but the opposite holds for SKECEs on the interdecadal timescale. As for frequency, the trend of SKECEs is obviously negative, and that of FKECEs is also negative during the pre-1990s epoch but becomes positive after the 1990s. In February, the frequency of TECEs is the highest among the winter months, which tends to decrease during the pre-1990s epoch but increase after the 1990s. Comparatively, in the 850 hPa wind field the northwesterly airflow (cold air surges from Lake Baikal) is weaker, and the northeastern counterpart (cold air surges from the Okhotsk Sea) is stronger during SKECEs than during FKECEs. In the E-P fluxes and divergence fields at 300 hPa, for both SKECEs and FKECEs, significant wave-like anomalies appear across Northeast China, and the Rossby wave propagation energy is weaker in SKECEs than in FKECEs. Harmonic analysis shows that the long wave and the ultra-long wave of geopotential height anomaly in the same phase can more easily lead to extreme cold events.
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