摘要: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1990年代以前也持续减少，但是1990年代之后急剧增加；2月份总的极端低温事件发生天数最多，其在1990年代以前要远大于12月和1月份，且在1990年代以前总体在减少，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300 hPa的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。
关键词:极端低温事件/
中国东北/
冬季/
罗斯贝波/
谐波分析
Abstract:Using the CN05.2 dataset of daily mean temperature for the period from 1961 to 2014, total extreme cold events (TECEs) are determined in the present study. These TECEs are classified into two categories according to the domain they affected in eastern China (East of 105°E in China), i.e., the first category of extreme cold events (FCECEs) that only affected Northeast China and the second category of extreme cold events (SCECEs) includes those that affected most of eastern China. Results show that the trend of intensity of FCECEs is significantly negative, but the opposite is true for that of SCECEs on the interdecadal timescale. As for the occurrence frequency, the trend for SCECEs is obviously negative, and that for FCECEs is also negative during the pre-1990s epoch but becomes positive after the 1990s. The occurrence frequency of TECEs is the highest in February among the winter months, and it tends to decrease during the pre-1990s epoch but increases after the 1990s. Northwesterly winds (cold air surges from Lake Baikal) at 850 hPa during SCECEs is stronger than that during FCECEs, and the opposite is true for northeasterly winds (cold air surges from the Okhotsk Sea). Analysis of the E-P flux and divergence field at 300 hPa indicates that significant wave-like anomalies appear across Northeast China during both SCECEs and FCECEs, and the Rossby wave energy propagation is weaker during SCECEs than during FCECEs. Harmonic analysis shows that the overlap of longwave trough and ultra-longwave geopotential height anomaly in the same phase can more easily lead to extreme cold event.
Key words:Extreme cold events/
Northeast China/
Winter/
Rossby wave/
Harmonic analysis
PDF全文下载地址:
http://www.iapjournals.ac.cn/dqkx/article/exportPdf?id=20180501
