ISSN 1000-0526
CN 11-2282/P
Change Characteristic and Typical Circulation Type of  Strong Cooling in Eastern Hexi Corridor

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    Using daily lowest temperature observation data of five meteorological stations in the east of Hexi Corridor during 1961-2010, the number of strong cooling [the lowest temperature drop rate is ≥ 8 (10)℃ and the minimum temperature is ≤ 4℃ in 24(48 h) in recent 50 years] was calculated. Climatic characteristics of spatiotemperal distribution and intensity of strong cooling were systematically analyzed with statistical methods. Then the ECMWF 500 hPa numerical forecast grid data (2.5°×2.5°) from 1991 to 2010 was used to analyze the strong cooling circulation features in this region. Finally, relations between strong cooling times and atmospheric circulation characteristics were studied. The results show that strong cooling times distribute differently in eastern Hexi Corridor and it is more obviously in highelevation mountains and northern desert edge than in oasis plain area due to the block of terrain, vegetation and mountains. Strong cool weather has obvious regional characteristics, and the times reduces with the increase of strong cooling station number. The decadal and annual times of strong cooling show a decreasing trend, and time series of strong cooling times has 4-6 year quasiperiodic variation, but no mutations. Such weather occurs mainly from January to May and from September to December, but most in April. Times of strong cooling with different intensities varies greatly reducing rapidly with the increase of cooling intensity. Intensity of 24 h strong cooling has a weak reducing tendency, while that of 48 h strong cooling shows a slightly increasing trend. Typical circulation of strong cooling weather in eastern Hexi Corridor is divided into two categories, including northwest airflow type and northern airflow type, and the number of northwest airflow type is more than that of northern airflow type. A significantly positive correlation exists between monthly strong cooling times and circulation characteristics including highaltitude cold air strength and cold air moving path, which means that a close relationship exists between strong cooling times and the highlevel cold air strength and cold air moving path. Intensity and moving path of highlevel cold air are strong signals for the forecasting of strong cooling weather.

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  • Received:December 13,2014
  • Revised:February 01,2016
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  • Online: July 05,2016
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