近50 a内蒙古冬季冷暖事件变化和大气环流异常分析

采用三分位方法，对内蒙古100个站1961-2010年冬季（11月至次年2月）和季内各月平均气温序列进行分析，确定了单站冷暖事件阈值，并将单站冷暖事件分为弱和强两个等级。以此为基础，采用相对比例，确定内蒙古全区和东、西部区域冷暖事件的界定方法及等级划分标准。结果表明：前期（1961-1987年）内蒙古只有强冷事件而未出现全区性强暖事件，后期（1988-2010年）则以强暖事件为主，但2000年以来强冷事件时有发生。针对内蒙古强冷暖事件，分析了同期北半球对流层大气环流的分布特征，结果表明：在强冷事件期间，北半球对流层中上部，乌拉尔山阻高和鄂霍次克海阻高异常，并伸向极区，使得亚洲区极涡明显偏南、偏强，地面西伯利亚高压异常强大；在强暖事件期间，乌拉尔山阻高和鄂霍次克海阻高偏弱，亚洲区极涡明显偏弱并向西向北收缩，地面西伯利亚高压明显偏弱。

Variation of Winter Cold/Warm Events and General Circulation Anomaly over Inner Mongolia in Recent 50 Years

Based on the data of average air temperature in winter and every month in November, December, January and February at 100 meteorological stations in Inner Mongolia during the period of 1961-2010, the equiprobability grade method was employed to discriminate the thresholds of cold/warm events at these stations, and the events were divided into strong and weak cases. The definition methods and grading standards of cold/warm events at these stations in west, east and whole Inner Mongolia were determined in terms of the relative proportion method. The results of the variation of winter cold/warm events were described. The response of general circulation anomalies to winter cold/warm events was investigated. The results showed that only the strong cold events occurred during the period of 1961-1987, but many strong warm events occurred during the period of 1988-2010. The strong cold events occurred occasionally since 2000. During the strong cold events, the enhanced Asia Polar Vortex moved remarkably southward due to the anomaly of northward movement of Urals and Okhotsk blocking highs in mid upper troposphere, and the Siberia high on the ground was much stronger than the normal cases. During the strong warm events, the weaken Asia Polar Vortex moved remarkably northwestward. The Siberia high on the ground and the Urals and Okhotsk blocking highs in mid upper troposphere were much weaker than the normal cases..