平流层NAM异常对乌拉尔山阻塞高压的影响

Influence of Stratospheric NAM Anomalies on the Ural Blocking High

使用NCEP/NCAR再分析资料,对53年(1958—2010年)冬季的平流层北半球环状模(NAM)正、负异常下传期间乌拉尔山阻塞高压的活动特征分别进行合成分析。结果表明,在平流层NAM负异常下传期间,阻塞高压事件的发生频次更高,生命期更长,并且在空间上发展得更加深厚。阻塞高压崩溃之后,冷空气主体偏北,所造成的我国北方地区降温也更强。通过对E-P通量分析发现,在NAM负异常下传期间,乌拉尔山区域的波动更容易向上传播,更有助于对流层乌拉尔山阻塞高压的维持和发展。这些结果对利用平流层环流异常信号预测我国北方冬季短期气候变率,尤其是寒潮天气有重要意义。

Using the NCEP/NCAR reanalysis over the period of 1958-2010, composite analysis of the Ural Blocking High relative to positive and negative stratospheric NAM anomalies is carried out, respectively. It is found that during negative stratospheric NAM anomalies, the Ural Blocking High has higher frequencies of occurrence, longer life cycle, stronger amplitude, and has stronger influences on Northern China. E-P flux analysis demonstrates that during negative stratospheric NAM anomalies, the vertical component of E-P fluxes over Ural Mountain region is stronger than that during positive NAM anomalies, suggesting that stratospheric circulations during negative NAM anomalies prefers upward wave propagation. The results have important implications for medium-range forecasting of winter weather or short-term climate variability in Northern China.