登陆福建台风外围环流中宁波地区强对流天气分析
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摘要
利用中央气象台台风定位定强、常规气象观测、浙江省自动气象站、宁波及华东多普勒天气雷达、美国NCEP/FNL(1°×1°)再分析等多种资料,对2015—2016年5个福建中南部沿海登陆后西北行的台风进行对比分析。这5个台风路径相似,宁波地区仅受外围环流影响,但均出现了暴雨到大暴雨,其中4个出现强对流。分析表明:浙江沿海保持较强的高层辐散和低层辐合,为强对流天气发生提供了环流背景。强对流天气发生在台风中心位于闽赣交界处、强度迅速减弱阶段,浙北沿海中低层处于台风气旋性环流、副热带高压环流和中纬度西风环流之间,宁波地区上空低层(约1.5 km以下)风向随时间变化不大,并可能出现逆时针旋转,1.5 km往上则为明显的顺时针旋转,风向在垂直方向上表现为随高度顺时针旋转且切变增大,同时中上层风速往往同时增大,进一步增大了风垂直切变,有利于强对流天气的发生,强对流均发生在风垂直切变(有时仅表现为风向切变)增强阶段。强对流天气发生在台风外围螺旋雨带中,但强对流回波走向与螺旋雨带明显不同,多个个例表现出由东南-西北逐步转为西南-东北走向,与中上层引导气流的变化一致。出现强对流的台风个例,宁波地区低层存在较明显的温度梯度,其他热力不稳定因素表现不明显,倒槽、中尺度涡旋等为需要密切关注的动力触发因子。最后归纳出此类台风强对流天气典型的高、中、低层大气环流配置模型,为预报提供参考。
The article analyzes the characteristics of severe convections in Ningbo caused by five typhoons from 2015 to 2016 that landed at the middle to southern coast of Fujian province and all headed northwest later. Research data inclucle the typhoon location and intensity data from the Central Meteorological Observatory, a variety of conventional observation data, the automatic weather station data in Zhejiang Province, the Doppler radar data from Ningbo and East China, and NCEP/FNL(1 °×1 °) reanalysis data.These five typhoons had similar tracks and all resulted in heavy rainfalls in Ningbo. Although affected only by the outer rain bands of these typhoons, four of them led to severe convective weather. Results showed that strong divergences at high levels and convergences at low levels over Zhejiang coastal areas provided suitable circulation background for the severe convections. Convective weather occurred when the typhoon centers were located near the border of Fujian and Jiangxi provinces, while typhoon intensities were decreasing rapidly. At lower to middle levels, the coastal areas of northern Zhejiang province were encircled by typhoon cyclonic circulations, subtropical high circulations, and mid-latitude westerly circulations. Over Ningbo, wind directions showed few changes with time at lower levels(below 1.5 km), with some counter clockwise rotations though; at higher levels, they displayed more obvious clockwise rotations with time. The winds were veering with height and the wind shears were increasing. At the same time, the wind speeds at the middle and upper levels were strengthened, leading to more vertical wind shears. All these were favorable for the initiation of severe convections. Strong convections all took place during the enhancement periods of vertical wind shears within the outer spiral rain bands of these typhoons. On the other hand, the movement orientations of the strong convection echoes were quite different from those of the typhoon outer rain bands, and tended to change from southeast-to-northwest to southwest-to-northeast eventually, in consistent with the steering flows at middle and high levels. In the strong convection cases, noticeable low level temperature gradients were observed, but other thermal instabilities were not obvious. Inverted typhoon troughs and mesoscale vortices deserve close attention as triggering factors for convections. To help improve local operational forecast a conceptual model has been summarized to describe the typical circulation patterns at high, middle and low levels for convection initiations in Ningbo caused by typhoon with landfalls in Fujian province.
The article analyzes the characteristics of severe convections in Ningbo caused by five typhoons from 2015 to 2016 that landed at the middle to southern coast of Fujian province and all headed northwest later. Research data inclucle the typhoon location and intensity data from the Central Meteorological Observatory, a variety of conventional observation data, the automatic weather station data in Zhejiang Province, the Doppler radar data from Ningbo and East China, and NCEP/FNL(1 °×1 °) reanalysis data.These five typhoons had similar tracks and all resulted in heavy rainfalls in Ningbo. Although affected only by the outer rain bands of these typhoons, four of them led to severe convective weather. Results showed that strong divergences at high levels and convergences at low levels over Zhejiang coastal areas provided suitable circulation background for the severe convections. Convective weather occurred when the typhoon centers were located near the border of Fujian and Jiangxi provinces, while typhoon intensities were decreasing rapidly. At lower to middle levels, the coastal areas of northern Zhejiang province were encircled by typhoon cyclonic circulations, subtropical high circulations, and mid-latitude westerly circulations. Over Ningbo, wind directions showed few changes with time at lower levels(below 1.5 km), with some counter clockwise rotations though; at higher levels, they displayed more obvious clockwise rotations with time. The winds were veering with height and the wind shears were increasing. At the same time, the wind speeds at the middle and upper levels were strengthened, leading to more vertical wind shears. All these were favorable for the initiation of severe convections. Strong convections all took place during the enhancement periods of vertical wind shears within the outer spiral rain bands of these typhoons. On the other hand, the movement orientations of the strong convection echoes were quite different from those of the typhoon outer rain bands, and tended to change from southeast-to-northwest to southwest-to-northeast eventually, in consistent with the steering flows at middle and high levels. In the strong convection cases, noticeable low level temperature gradients were observed, but other thermal instabilities were not obvious. Inverted typhoon troughs and mesoscale vortices deserve close attention as triggering factors for convections. To help improve local operational forecast a conceptual model has been summarized to describe the typical circulation patterns at high, middle and low levels for convection initiations in Ningbo caused by typhoon with landfalls in Fujian province.
引文
[1]曾明剑,吴海英,郑媛媛. 0808号台风“凤凰”登陆衰减后空间结构与再生对流云团演变特征分析[J].热带气象学报, 2015, 31(6):782-795.
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[9]郑峰,钟建锋,张灵杰.超强台风“圣帕”引发温州类龙卷的特征分析[J].高原气象, 2012, 31(1):231-238.
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[11]郑媛媛,张备,王啸华,等.台风龙卷的环境背景和雷达回波结构分析[J].气象, 2015, 41(8):942-952.
[12] CRAVEN J P, BROOKS H E. Baseline climatology of sounding derived parameters associated with deep moist convection[J]. Nat Wea Dig,2004, 28(1):13-24.
[13] GRAMS J S, THOMPSON R L, SNIVELY D V, et al. A climatology and comparison of parameters for significant tornado events in the United States[J]. Wea Forecasting, 2012, 27(1):106-123.
[14] MENG Z Y, ZHANG Y J. On the squall lines preceding landfalling tropical cyclones in China[J]. Mon Wea Rev, 2012, 140(2):445-470.
[15]李兆慧,王东海. 2015年10月4日佛山龙卷过程的观测分析[J].气象学报, 2017, 75(2):288-313.
[16]唐民,梅珏.上海浦东机场一次连续出现的强对流天气对比分析[J].气象, 2009, 35(10):25-31.
[17]何彩芬,姚秀萍,胡春蕾,等.一次台风前部龙卷的多普勒天气雷达分析[J].应用气象学报, 2006, 17(3):370-375.
[18]程正泉,陈联寿,李英.登陆台风降水的大尺度环流诊断分析[J].气象学报, 2009, 67(5):840-850.
[19]孙继松,陶祖钰.强对流天气分析与预报中的若干基本问题[J].气象, 2012, 38(2):164-173.
[20]梁俊平,张一平. 2013年8月河南三次西南气流型强对流天气分析[J].气象, 2015, 41(11):1 328-1 340.
[21]郑永光,陶祖钰,俞小鼎.强对流天气预报的一些基本问题[J].气象, 2017, 43(6):641-652.
[22]刘健文,郭虎,李耀东,等.天气分析预报物理量计算基础[M].北京:气象出版社, 2005:117-119.
[23]朱乾根,林锦瑞,寿绍文,等.天气学原理和方法(第三版)[M].北京:气象出版社, 2000:435.
[2]姚日升,涂小萍,俞芳芳,等. 1614号超强台风“莫兰蒂”在浙江沿海降水预报偏小的原因[J].热带气象学报, 2018, 34(5):637-644.
[3]钮学新,董加斌,杜惠良.华东地区台风降水及影响降水因素的气候分析[J].应用气象学报, 2005, 16(3):402-407.
[4]董美莹,陈锋,许娈,等.浙江热带气旋倒槽暴雨气候特征研究[J].热带气象学报, 2017, 33(1):84-92.
[5] MENG Z Y, YAN D C, ZHANG Y J. General features of squall lines in East China[J]. Mon Wea Rev, 2013, 141(5):1 629-1 647.
[6]周海波,白爱娟,蔡亲波,等.对强台风“纳沙”(1117)登陆海南岛前后降水非对称性的分析[J].热带气象学报, 2017, 33(3):386-398.
[7]李彩玲,炎利军,李兆慧,等. 1522号台风“彩虹”外围佛山强龙卷特征分析[J].热带气象学报, 2016, 32(3):416-424.
[8]郑峰,钟建锋,娄伟平.圣帕(0709)台风外围温州强龙卷风特征分析[J].高原气象, 2010, 29(2):506-513.
[9]郑峰,钟建锋,张灵杰.超强台风“圣帕”引发温州类龙卷的特征分析[J].高原气象, 2012, 31(1):231-238.
[10] MCCAUL E W. Buoyancy and shear characteristics of hurricane-tornado environments[J]. Mon Wea Rev, 1991, 119(8):1 954-1 978.
[11]郑媛媛,张备,王啸华,等.台风龙卷的环境背景和雷达回波结构分析[J].气象, 2015, 41(8):942-952.
[12] CRAVEN J P, BROOKS H E. Baseline climatology of sounding derived parameters associated with deep moist convection[J]. Nat Wea Dig,2004, 28(1):13-24.
[13] GRAMS J S, THOMPSON R L, SNIVELY D V, et al. A climatology and comparison of parameters for significant tornado events in the United States[J]. Wea Forecasting, 2012, 27(1):106-123.
[14] MENG Z Y, ZHANG Y J. On the squall lines preceding landfalling tropical cyclones in China[J]. Mon Wea Rev, 2012, 140(2):445-470.
[15]李兆慧,王东海. 2015年10月4日佛山龙卷过程的观测分析[J].气象学报, 2017, 75(2):288-313.
[16]唐民,梅珏.上海浦东机场一次连续出现的强对流天气对比分析[J].气象, 2009, 35(10):25-31.
[17]何彩芬,姚秀萍,胡春蕾,等.一次台风前部龙卷的多普勒天气雷达分析[J].应用气象学报, 2006, 17(3):370-375.
[18]程正泉,陈联寿,李英.登陆台风降水的大尺度环流诊断分析[J].气象学报, 2009, 67(5):840-850.
[19]孙继松,陶祖钰.强对流天气分析与预报中的若干基本问题[J].气象, 2012, 38(2):164-173.
[20]梁俊平,张一平. 2013年8月河南三次西南气流型强对流天气分析[J].气象, 2015, 41(11):1 328-1 340.
[21]郑永光,陶祖钰,俞小鼎.强对流天气预报的一些基本问题[J].气象, 2017, 43(6):641-652.
[22]刘健文,郭虎,李耀东,等.天气分析预报物理量计算基础[M].北京:气象出版社, 2005:117-119.
[23]朱乾根,林锦瑞,寿绍文,等.天气学原理和方法(第三版)[M].北京:气象出版社, 2000:435.