2007年冬季西伯利亚高压季节内变化对云南气温的影响

应用NCEP/NCAR再分析资料中风场、温度场、气压场和位势高度场资料,以及云南96个站点的气温资料,分析2007年冬季西伯利亚高压的季节内变化特征,及对云南2007年冬季气温的影响.结果表明:2007年冬季云南平均气温和西伯利亚高压均具有显著的10～20 d和30～60 d振荡特征.冬季的4次强降温过程主要受云南平均气温10～20 d振荡的控制,而其30～60 d振荡则是提供大的背景场.2007年冬季,云南平均气温与西伯利亚高压存在超过95%显著性检验的滞后负相关关系,其中滞后18 d左右时负相关值最大.分析4次强降温过程前期的大气环流背景可知,当西伯利亚高压30～60 d振荡处于负位相时,大气10～20 d振荡环流表现出西伯利亚高压发展、盛期、南压和减弱4个时期,后期云南的降温受高压盛期和南压的影响大;而当西伯利亚高压处于30～60 d振荡的正位相时,大气10～20 d振荡环流特征表现为阻塞高压持续维持、冷空气持续向南传播的特征,导致后期云南降温持续时间久,降温幅度大.可见,影响云南地区冷空气的强弱不仅与西伯利亚高压30～60 d振荡有关,与10～20 d振荡也有直接的关系.

The Inter-seasonal Oscillation of Siberian High influenced on the winter temperature of Yunnan in 2007

Using daily observations of surface air temperature in Yunnan and NCEP/NCAR daily data during winter from 1961 to 2008,the characteristics of the low frequency oscillation on the temperature in Yunnan are studied by the methods of power spectrum analysis and Lanczos filter.The results show that the characteristic of biweekly oscillation on the temperature in Yunnan is distinctness,especially that in 2007/2008 winter.Analysis the circulation system in 2007/2008 winter,when the 30—60 d oscillation on Siberian High exists the negative phase,superposition of the 10—20 d oscillation on Siberian High make the characteristics of the 10—20 d oscillation on circulation system shows that cold wave developed,broken out and died out.When the 30—60 d oscillation on Siberian High exists the positive phase,superposition of the 10—20 d oscillation on Siberian High make the blocking high hold out and strong cold air southerly propagate.It is obviously that the degree of cold air affected Yunnan is not only related with 30—60 d oscillation on Siberian High,but also with 10—20 d oscillation on Siberian High.