高级检索

东亚冬季大范围长时间气温反相事件及成因探究

East Asia Large-Scale Temperature Reversal Events in Winter and the Exploration of Their Cause

  • 摘要: 东亚冬季气温存在显著的季节内冷暖起伏,给人民的生产生活带来了深远的影响。本文主要使用1980~2022年冬季逐日NCEP-NCAR再分析资料,筛选42年冬季中最典型的“冷转暖”事件和“暖转冷”事件,分析了东亚冬季大范围、长时间的气温反相事件的特征及其主要影响因子。结果表明:(1)在42年冬季中存在典型的21个“冷转暖”事件及6个“暖转冷”事件,偏暖和偏冷之间的气温差均高达10°C以上,维持时间超30天,并且“冷转暖”事件和“暖转冷”事件均表现出全区一致的冷暖转相。(2)无论是“冷转暖”事件还是“暖转冷”事件,在温度转相前2天左右乌拉尔山地区的位势高度先发生位相转变。在暖转冷事件中,伴随着乌拉尔山地区位势高度异常由负转正,2天后东亚气温将由偏暖转为偏冷,反之亦然。(3)“暖转冷”事件中,乌拉尔山地区位势高度异常的转向与北大西洋涛动(North Atlantic oscillation,NAO)南中心密切相关,在温度转向前35天NAO南中心在平流层已出现位势高度正异常信号,并下传至对流层,形成波作用通量向东传播至乌拉尔山地区,使得其位势高度由负转正,进而造成东亚气温反转。“冷转暖”事件则主要与NAO的北中心有关,温度转向前30天位势高度负异常已出现在平流层,并下传至对流层进一步造成乌拉尔山地区位势高度转向。NAO南、北中心位势高度在平流层的信号变异与相应气温转向事件中气温的30天超前相关系数高达−0.8,因此,对它的监测和预测将有利于我们提前30天预测东亚冬季气温大范围、长时间的季节内转向。

     

    Abstract: Winter temperatures in East Asia exhibit significant subseasonal oscillations, profoundly affecting production and daily life. Using NCEP-NCAR reanalysis data from 1980 to 2022, the most typical winter temperature reversal events over the past 42 years were identified and analyzed. This analysis focused on their characteristics and main influencing factors, employing correlation analysis, power spectrum analysis, Butterworth filter, Plumb wave activity flux analysis, and other statistical methods. Key results include: (1) The analysis of 42 winters identified 21 typical “cold-to-warm” events (CTWEs) and 6 “warm-to-cold” events (WTCEs). In all events, the temperature difference between the warm and cold periods exceeded 10°C. Temperature reversals were observed over the whole region. (2) In all events, a phase transition in the 500-hPa geopotential height anomaly over the Ural Mountains occurred 2 days before the East Asian temperature reversal. During WTCEs, this anomaly shifted from negative to positive, leading to a warm-to-cold temperature change in East Asia after two days and vice versa. (3) Further analysis reveals that WTCE reversals are closely related to the southern center of the North Atlantic oscillation (NAO). Thirty-five days before the temperature reversal in East Asia, a positive geopotential height anomaly was observed in the southern center of NAO in the stratosphere. This anomaly propagated downward to the troposphere, exciting a wave flux that moved eastward toward the Ural Mountains region, leading to a transition of the geopotential height anomaly from negative to positive in that region. However, the CTWEs were mainly affected by the northern center of NAO, where a negative geopotential height anomaly was present in the northern center of NAO in the stratosphere 30 days before the East Asian temperature anomaly reversal. The 30-day leading correlation coefficient between the geopotential height changes in the NAO centers and the corresponding temperature anomalies in different reversal events is as high as −0.8, exceeding the 95% confidence level. Therefore, by monitoring the geopotential heights in the southern and northern NAO centers in the stratosphere, we can predict East Asian winter temperature reversals up to 30 days in advance.

     

/

返回文章
返回