ISSN 1006-9895

CN 11-1768/O4

The Euro-Asia Height Positive Anomalies Character and Its Probable Influence on Regional Extreme Low-Temperature Events in Winter in China
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    Abstract:

    Based on observation data and NCEP/NCAR reanalysis data, the 500-hPa height positive anomalies mode of Euro-Asia and its probable influence on regional extreme low-temperature events (RELTEs) in China during winter are investigated. The results indicate that the probability of positive anomalies occurring in one of three areas (Ural, Baikal, or Okhotsk) is 0.83 when there is a RELTE, suggesting that the height anomalies mode in high areas of the Euro-Asia blocking might be directly responsible for such RELTEs. The modes with positive height anomalies are divided into 7 types, with positive anomalies in Ural, Baikal, Okhotsk, Ural-Baikal, Ural-Baikal-Okhotsk, Ural-Okhotsk, and Baikal-Okhotsk. Each RELTE corresponds to a different anomaly mode, with differences in spatial distribution, duration, and intensity. For example, the positive anomalies modes of Ural-Baikal and Ural-Okhotsk always correspond to RELTEs affecting all of China and northeast-northern China, with average durations of 14.2 and 14.1 days, respectively. Furthermore, each type of positive height anomaly provides advance warning of the RELTEs, with average lead times of up to 1-8 days. The spatial distribution of average advance days and the development of height before or after the first day of RELTEs also suggest that the positive height anomalies mode could develop from two directions: west of Ural or east of Okhotsk. This further validates the probability of the advance warning for RETLEs.

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History
  • Received:August 24,2012
  • Revised:February 22,2013
  • Adopted:
  • Online: October 23,2013
  • Published: