| 夏季乌拉尔地区大气环流持续异常的形成与维持 |
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| 作者姓名： | Li Shuanglin Ji Liren Lin Wantao |
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| 作者单位： | Li Shuanglin，Ji Liren and Lin Wantao LASG，Institute of Atmospheric Physics，Chinese Academy of Sciences，Beijing 100029 |
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| 基金项目： | This work is supported by the CAS Key Project KZCX2-203, the Research Program for the Out-
standing State Key Laboratory (Grant |
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| 摘 要： | 从天气尺度瞬变涡旋与时间平均基本气流双向相互作用建立异常型的角度，研究了夏季乌拉尔地区大气环流持续异常的形成与维持，首先基于合成分析，研究了持续异常期间的天气尺度瞬变波活动情况，结果表明：正异常时，在上游地区，从北大西洋中部到西欧沿岸，瞬变活动明显增强。负异常过程时相反，该地区瞬变活动减弱。利用线性正压原始方程模式，研究了在合成正异常基本流及7月气候基本流等两种基本流下，正异常时上游异常瞬变活动对异常建立的贡献。结果表明：正异常时，上游增强的瞬变波活动有利于正异常的建立与维持。利用基于线性正压原始方程模式设计的风暴轴模式，研究了时间平均基本流在组织与调控瞬变活动中所起的作用。结果表明：当乌拉尔地区高压脊发展时，有利于瞬变在上游的北大西洋中部到西欧沿岸地区组织起来。脊发展越强，越有利。结合上述两方面的结果，提出了瞬变与行星波双向相互作用的乌拉尔持续正异常形成和自维持机制。
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| 关 键 词： | 持续异常 风暴轴 行星波 双向相互作用 |
On the Formation and Maintenance of the Persistent Anomalies of Summertime Circulation over the Ural Mountains |
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| Li Shuanglin,Ji Liren,Lin Wantao.On the Formation and Maintenance of the Persistent Anomalies of Summertime Circulation over the Ural Mountains[J].Advances in Atmospheric Sciences,2001,18(5):819-830. |
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| Authors: | Li Shuanglin Ji Liren and Lin Wantao |
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| Institution: | LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | The formation and maintenance of the persistent anomalies (PA hereafter) of summertime circulation over the Ural Mountains are studied, and a two-way interaction of transient eddies and time-mean flow that may be involved in the evolution of the positive anomaly is demonstrated. Firstly the feature of synoptic-scale transient activity during the PA period is investigated based on composite, and the results suggest a significant enhancement of transient activity over the sector from the central North Atlantic to the coastal western Europe for the positive cases whereas a weakening is for the negative. Numerical simulations are conducted using a barotropic primitive equation model linearized about two time-mean flows, the com posite of positive cases and the climatological July mean respectively. The results show that the enhanced transient activity upstream will favor positive height anomalies over the Ural Mountains. A barotropic stormtrack model is developed, by which the role of time-mean flow in organization and modulation of transient eddies is studied. It is shown that the growth of ridge over the Ural Mountains tends to organize transient eddies into the region upstream from the central North Atlantic to the coastal western Europe. Combining the two aspects, a positive feedback mechanism through two-direction interaction of transient eddies and basic flow is proposed, which can be responsible for the formation and maintenance of the per sistent positive anomalies over the Ural Mountains. |
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| Keywords: | Persistent anomaly Transient forcing Planetary wave Two-way interaction |
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