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Advances in Atmospheric Sciences

, Volume 18, Issue 5, pp 819–830 | Cite as

On the Formation and Maintenance of the Persistent Anomalies of Summertime Circulation over the Ural Mountains

  • Li Shuanglin
  • Ji Liren
  • Lin Wantao
Article

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 composite 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 persistent positive anomalies over the Ural Mountains.

Key words

Persistent anomaly Transient forcing Planetary wave Two-way interaction 

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Copyright information

© Advances in Atmospheric Sciences 2001

Authors and Affiliations

  • Li Shuanglin
    • 1
  • Ji Liren
    • 1
  • Lin Wantao
    • 1
  1. 1.LASG, Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina

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