夏季乌拉尔长阻塞过程及其与热带热力异常关系个例分析

基金:  国家重点基础研究发展计划项目(973计划)2009CB421401
中文关键词:  乌拉尔持续异常  行星波  热带对流
英文关键词:  Persistent anomaly over the Ural Mountains  Planetary wave  Tropical convection
　　 　　 　　
作者中文名        作者英文名        单位
李子仪        LI Ziyi        成都信息工程学院大气科学学院,成都 6102252;中国科学院大气物理研究所竺可桢—南森国际研究中心,北京 100029;中国民用航空华东地区空中交通管理局浙江分局,杭州 311207
李双林        LI Shuanglin        中国科学院大气物理研究所竺可桢—南森国际研究中心,北京 100029
李国平        LI Guoping        成都信息工程学院大气科学学院,成都 6102252
引用:李子仪,李双林,李国平.2013.夏季乌拉尔长阻塞过程及其与热带热力异常关系个例分析[J].大气科学,37(3):731-744,doi:10.3878/j.issn.1006-9895.2012.12006.
Citation:LI Ziyi,LI Shuanglin and LI Guoping.2013.Analysis of Longstanding Summer Blocking Highs over the Ural Mountains and Their Relationship with Tropical Thermal Anomalies[J].Chinese Journal of Atmospheric Sciences (in Chinese),37(3):731-744,doi:10.3878/j.issn.1006-9895.2012.12006.
中文摘要:
      2010和1998年均为长江洪涝年,这两年大气环流的一个共同特征是乌拉尔阻塞的频繁发生和异常维持。利用NCEP/NCAR逐日再分析的大气环流资料和向上射出长波辐射资料,对比分析了2010和1998年夏季乌拉尔地区环流持续异常的特征、大尺度环流形势、热带加热背景及其可能影响。结果显示：(1)2010年夏季乌拉尔发生了一次持续正异常过程,该过程是自1948年以来持续时间第二长(共37天)的,其最大异常中心在乌拉尔略偏西,持续时间比1998年的那次过程长(1998年的那次过程持续时间为22天)；(2)异常过程期间存在行星波活动异常,2010年的过程行星波活动以2、4波的贡献为主,而1998年为1、2波的贡献为主；(3)异常过程期间,热带对流活动存在显著差异。这可能是它们行星波活动不同的原因；(4)两次异常过程期间,一个共同特点是在苏门答腊西侧的热带印度洋区域存在明显的对流增强。该区域强对流可能激发了类似东亚—太平洋遥相关型的波列向中高纬传播,从而调制行星波活动,再影响乌拉尔位势高度异常的形成和持续维持。
Abstract:
      Severe floods occurred in the Yangtze River valley in 1998 and 2010. The atmospheric circulation patterns responsible for the disastrous events share a common feature: frequent occurrence and persistent presence of the blocking high over the Ural Mountains. To understand the formation and longstanding presence of the Ural blocking high, a comparative analysis was conducted by utilizing the daily data from the NCEP/NCAR reanalysis. The results suggest that (1) a significant positive persistent anomaly event occurred over the Ural in the summer of 2010, which was the second longest (37 days) since 1948 with the peak of the anomaly located slightly west of the Ural, whereas the 1998 event was shorter (22 days). (2) Significant abnormal planetary wave activities were seen in both cases. The planetary wave components with wavenumbers 2 and 4 played a dominant role in the 2010 case, but those with wavenumbers 1 and 2 were more important in the 1998 case. (3) Significant abnormal convections occurred over the tropics, which may have modulated the planetary wave activity and were responsible for the difference between the cases. (4) An intensified convection pattern emerged in the east tropical Indian Ocean region west of Sumatra in both cases. It might have significantly contributed to the geopotential height anomaly chain originating from the tropical Indian-Pacific Ocean and propagating toward the middle and high latitudinal Pacific; thus, the anomalous planetary wave activities excited a wave-train similar to the well-known East-Asian Pacific pattern.