2018年初豫南特大暴雪过程的特征与成因分析
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摘要
利用常规观测资料及NCEP/NCAR 1°×1°逐6 h再分析资料,分析了2018年初豫南特大暴雪过程的特征与成因。结果表明:此次特大暴雪过程发生在500 hPa乌拉尔山以东地区阻塞高压稳定维持和中、高纬地区多支短波槽东移并同位相叠加的环流背景下,具有持续时间长、过程降雪量大、降雪强度大、积雪深等特征;强降雪阶段,对流层低层豫南地区同时存在两个水汽来源,一是700 hPa西南急流对孟加拉湾水汽的输送,二是850 hPa东南气流对东海南部水汽的输送;低层较强的水汽输送及辐合、贯穿整个对流层的湿层、维持较高的比湿和整层可降水量对暴雪的形成与持续有一定的指示意义;低空冷垫有利于逆温层之上西南暖湿气流在其上爬升,低空垂直风切变的变化对降雪强度变化有较好的指示意义;高空急流先于低空西南急流而建立,高空急流轴南压使得低空急流发展北上,高低空急流耦合激发次级环流圈上升支,为暴雪发生发展提供了强烈的上升运动;对流层低层700 hPa与850 h Pa持续强烈锋生,有利于暴雪加强和持续。
Based on conventional observation data and NCEP/NCAR 6-hour reanalysis data with 1°×1° resolution, we analyzed the characteristics and causes of a heavy snowstorm event in southern Henan in the beginning of January 2018. The results show that this event, which is characterized by long duration, more total snowfall, large precipitation intensity and deep snow cover, occurred under a circulation environment of the stable maintenance of blocking high in eastern part of Ural Mountains in 500 h Pa with multiple short wave troughs moving westward and superposing in same phase in the mid-and high-latitudes. During the severe snowfall period of this event, there are two sources supplying water vapor to southern Henan in the lower troposphere, i.e., the water vapor transported by 700 hPa southwest jet from the Bay of Bengal and by 850 hPa southeast airflow from the south of the East China Sea, respectively. The intensive transportion and convergence of water vapor in the low-level, the wet layer through whole troposphere and the continuance of high specific humidity and whole layer precipitable water are of good indicative for the origination and continuance of snowstorm. The cold cushion in the low-level is helpful for southwest warm and wet airflow climbing above the inversion layer, and the variation of vertical wind shear in the low-level is a better indication for the change of snowfall intensity. The establishment of the high-level jet stream precedes that of southwesterly low-level jet. The southward movement of high-level jet axis makes the low-level jet develop northward, and the coupling of the high-level jet and the low-level jet stimulates the ascending branch of the secondary circulation, which provides the intensive ascending movement for the occurrence and development of snowstorm. The frontogenesis in 700 hPa and 850 hPa in the lower troposphere is conducive to the strengthening and continuation of snowstorm.
Based on conventional observation data and NCEP/NCAR 6-hour reanalysis data with 1°×1° resolution, we analyzed the characteristics and causes of a heavy snowstorm event in southern Henan in the beginning of January 2018. The results show that this event, which is characterized by long duration, more total snowfall, large precipitation intensity and deep snow cover, occurred under a circulation environment of the stable maintenance of blocking high in eastern part of Ural Mountains in 500 h Pa with multiple short wave troughs moving westward and superposing in same phase in the mid-and high-latitudes. During the severe snowfall period of this event, there are two sources supplying water vapor to southern Henan in the lower troposphere, i.e., the water vapor transported by 700 hPa southwest jet from the Bay of Bengal and by 850 hPa southeast airflow from the south of the East China Sea, respectively. The intensive transportion and convergence of water vapor in the low-level, the wet layer through whole troposphere and the continuance of high specific humidity and whole layer precipitable water are of good indicative for the origination and continuance of snowstorm. The cold cushion in the low-level is helpful for southwest warm and wet airflow climbing above the inversion layer, and the variation of vertical wind shear in the low-level is a better indication for the change of snowfall intensity. The establishment of the high-level jet stream precedes that of southwesterly low-level jet. The southward movement of high-level jet axis makes the low-level jet develop northward, and the coupling of the high-level jet and the low-level jet stimulates the ascending branch of the secondary circulation, which provides the intensive ascending movement for the occurrence and development of snowstorm. The frontogenesis in 700 hPa and 850 hPa in the lower troposphere is conducive to the strengthening and continuation of snowstorm.
引文
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[2]张迎新,张守保.华北平原回流天气的结构特征[J].南京气象学院学报,2006,29(1):107-113
[3]侯瑞钦,张迎新,范俊红,等.2009年深秋河北省特大暴雪天气成因分析[J].气象,2011,37(11):1 352-1 359
[4]陈雪珍,穆建丽,赵桂香,等.华北暴雪过程中的急流特征分析[J].高原气象,2014,33(4):1 609-1 075
[5]周雪松,谈哲敏.华北回流暴雪发展机理个例研究[J].气象, 2008,34(1):18-26
[6]田秀霞,李娟,何丽华,等.2011年初冬华北南部回流暴雪诊断分析[J].暴雨灾害,2016,34(3):243-251
[7]孙仲毅,王军,靳冰凌,等.河南省北部一次暴雪天气过程诊断分析.高原气象,2010,29(5):1 338-1 344
[8]宋清芝,孙静兰,吕晓娜.河南省一次暴雪伴雷电天气的形成机理[J].气象,2011,37(5):583-589
[9]张宁,张萍萍,龙利民,等.2010年1月鄂东一次暴雪过程中尺度分析[J].暴雨灾害,2013,32(1):46-52
[10]陈红专,叶成志,龙丽华.2011年1月湖南罕见持续性暴雪天气成因分析[J].暴雨灾害,2012,31(2):141-148
[11]黄安丽,高坤.对流层高、低空急流耦合作用的动力学分析[J].浙江大学学报:理学版,1982,9(3):356-364
[12]钟中,元慧慧,李杰,等.一次高空急流增强过程中的中尺度扰动和动量输送特征[J].气象科学,2010,30(5):639-645
[13] Uccellini L W, Johnson D R. The coupling of upper and lower tropospheric jet stream and implication for the development of severe convective storm[J]. Mon Wea Rew, 1979, 107(6):682-703
[14]李兆慧,王东海,王建捷,等.一次暴雪过程的锋生函数和急流——锋面次级环流分析[J].高原气象,2011,30(6):1 505-1 515