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5类南岳高山气象站风场对湖南不同天气型强降水的指示作用

Indicative significance of five patterns of wind at the Nanyue Mountain Meteorological Stationon various severe precipitation events in Hunan

  • 摘要: 利用2006—2014 年4—9 月常规高空、地面观测资料以及同期南岳高山气象站(简称南岳站)逐时风场资料和湖南省96 个常规观测站逐时雨量资料,对同期117 例强降水天气过程进行天气影响系统分型,并分析5 类南岳站风场型对湖南不同天气型强降水预报的指示作用。结果表明: 南岳站风场在6 种天气型强降水天气过程中主要有5 种不同表现型,其中4 类逐时风场演变特征对湖南强降水带移动和强度变化有较好的指示作用。该站南风超过10 m·s-1的时刻较湘北和湘西北地区开始出现强降水通常有2~6 h 的预报提前量,达到急流标准(12 m·s-1)的时刻较湘中以北地区降水达到最强提前2~5 h,南风剧减至8 m·s-1以下或转为北风的时刻较湘南地区降水加强有2~4 h 的预报提前量。当南岳站主导风为南风且风速在12~14 m·s-1之间时,湘西北和湘北降水强度最大,但当该站南风超过14 m·s-1时,雨区将北抬至长江以北。当该站主导风为北风且风速在1~3 m·s-1之间时,湘中和湘西南降水较强;当其在3~5 m·s-1之间时,湘中、湘西南、湘东南地区均有降水;当其超过5 m·s-1时,湘中和湘西南降水减弱或停止,湘东南降水则加强。台风暴雨期间,该站出现明显的南北风交替且风速基本在5 m·s-1以下时,强降水区一般位于湘东南。

     

    Abstract: Using routine upper-air and surface observations, hourly wind variations at the Nanyue Mountain Meteorological Station (called Nanyue Station for short) and hourly rainfall data of 96 meteorological stations over Hunan between April and September from 2006 to 2014,we make a synoptic system classification for 117 severe precipitation cases during the corresponding period, and then discuss the indicative significance of five wind patterns at Nanyue Station on different types of severe precipitation forecast in Hunan. The results indicate that there are 5 different types of wind variations at Nanyue Mountain, which correspond to 6 different patterns of severe precipitation events in Hunan.Of the five hourly wind variation patterns, four have indicative significance to the change of the movement and intensity of the severe precipitation belt. The time when south wind at Nanyue Station exceeds 10 m·s-1 is about 2-6 hours ahead of severe precipitation beginning in northern and northwestern Hunan. When the south wind reaches the low-level-jet criterion of 12 m·s-1, the strongest precipitation can be expected to occur in central and northern Hunan about 2-5 h later. It usually has forecast lead time of 2-4 h for enhanced rain in southern Hunan when the south wind at Nanyue falls below 8 m·s-1 or shifts to north wind. When the dominant condition at Nanyue is south wind of 12-14 m·s-1, the most severe precipitation always occurs in northern and northwestern Hunan. If the wind speed at Nanyue exceeds 14 m·s-1, rain area will move northwards to the north parts of the Yangtse River. When the dominant at Nanyue is north wind of 1-3 m·s-1, moderate to severe precipitation occurs in central and southwestern Hunan. When the northerly wind speed is between 3-5 m·s-1, precipitation will occurs in central,southwestern and southeastern Hunan. If northerly wind exceeds 5 m·s-1, precipitation in central a d southwestern Hunan will weaken or stop completely, but in southeastern Hunan it will increase. During the heavy rain period caused by typhoon, if wind at Nanyue appears north andsouth erratically alternating and the wind speed is less than 5 m·s-1, severe precipitation usually occurs in southeastern Hunan.

     

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