The Statistical Analysis of Low Vortex During Meiyu Season in the Lower Reaches of the Yangtze

Yang Yinming; Gu Wenlong; Zhao Ruilei3; Liu Jie

Vol.21, NO.1, 2010

Article Contents

Article Navigation > Journal of Applied Meteorological Science > 2010 > 21(1): 11-18

Yang Yinming, Gu Wenlong, Zhao Ruilei3, et al. The statistical analysis of low vortex during Meiyu season in the lower reaches of the Yangtze. J Appl Meteor Sci, 2010, 21(1): 11-18.

Citation:

Yang Yinming, Gu Wenlong, Zhao Ruilei3, et al. The statistical analysis of low vortex during Meiyu season in the lower reaches of the Yangtze. J Appl Meteor Sci, 2010, 21(1): 11-18.

Yang Yinming, Gu Wenlong, Zhao Ruilei3, et al. The statistical analysis of low vortex during Meiyu season in the lower reaches of the Yangtze. J Appl Meteor Sci, 2010, 21(1): 11-18.

Citation:

Yang Yinming, Gu Wenlong, Zhao Ruilei3, et al. The statistical analysis of low vortex during Meiyu season in the lower reaches of the Yangtze. J Appl Meteor Sci, 2010, 21(1): 11-18.

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The Statistical Analysis of Low Vortex During Meiyu Season in the Lower Reaches of the Yangtze

1.
Shanghai Center of Satellite Remote Sensing and App lication, Shanghai 201100
2.
Zhongnan Meteoroloy Center of CA AC, Guangzhou 510405
3.
H uadong Meteoroloy Center of CAAC, Shanghai 200335

Received Date: 2009-02-25
Rev Recd Date: 2009-11-27
Publish Date: 2010-02-28

Abstract

Abstract

Local generated mesoscale vortexes (LMVs) in the lower reaches of the Yangtze is one key factor to improve rainstorm forecast accuracy since they can efficiently trigger and organize mesoscale convective systems (MCSs). There are many case studies focusing on the MCSs caused by LMVs, but in order to improve operational weather forecast ability during Meiyu season, the study about LMVs activities, structures and formative environment are necessary. Based on conventional weather data, satellite cloud images and numerical weather predictive outputs during Meiyu season of 1998—2005, the activities and structures of LMVs related to rainstorms in the lower reaches of the Yangtze are statistically analyzed, including the vortex generation, movement, life cycle, spatial range and related convective activities etc. Large scale environments and physical conditions are also synthetically analyzed. The result shows that LMVs in the lower reaches of Yangtze mainly generated around the Dabie Mountain area in Anhui Province. Typically, their horizontal scale changes from 100 km to 400 km, and most of them vary from 200 km to 300 km. Their vertical developing height usually changes from 1000 hPa to 700 hPa. LMVs moves mainly in two directions, one is northeast to as far as the Yellow Sea through north of Shandong Province, ant the other is southeastward towards the East China Sea through south of Jiangsu Province or north of Zhejiang Province. The life cycle of LMVs is less than 48 hours and it has no clear relations with their spatial scales. About 70% LMVs trigger single MCS or series MCSs and can lead to rainstorms. Rainstorms mainly happen to the south or southeast of LMVs, where there are enough warm and moisture flow. LMVs generated at the bottom of upper level trough of 500 hPa are especially possible to cause rainstorms. Analysis of large scale environments and physical conditions show more than 90% of LMVs develops at the bottom or in front of upper level trough at 500 hPa. The positive vorticity advection in front of upper level trough is necessary to LMVs generation and development. While the other conditions such as low level and upper level jet, middle level turbulence, low level moisture transfer and topographic conditions are all important to LMVs generation and development. Further studies such as mechanisms about LMV generation, development and the mechanisms about LMV trigger and organize MCSs are necessary.
- mesoscale low vortex;
- Meiyu front;
- rain storm;
- synthetically analysis

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References(16)

Figures and Tables

图 1 长江下游LM V移动路径

Fig. 1 Moving path of the LMV in the lower reaches of the Yangtze

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图 2 长江下游LMV的尺度特征 (a) 水平尺度，(b) 垂直发展高度

Fig. 2 Scale features of the LMV in the lower reaches of the Yangtze (a) horizontal scale, (b) vertical deve loping height

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图 3 长江下游LMV生命期

Fig. 3 The life cycle features of the LM Vin the lowerr eaches of the Yangtze

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图 4 暴雨区中心相对于LMV中心位置 (矩形框数字代表多次MCS，三角框数字代表强MCS，无框数字代表弱MCS)

Fig. 4 The rainso trm position relative to the center of low vortex (the number with rectangular box represents as serial MCSs, the number with triangle box represents as severe MCSs, and the number without box represent sas weak MCSs)

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图 5 LMV生成时500 hPa位势高度场 (单位:dagpm) 和风场

(a)2004年6月12日, (b)1998年7月21日, (c)1999年6月29日 (图中粗短线为槽线，“D”表示LMV位置)

Fig. 5 The observed 500 hPa geo potential height fields (unit :dagpm) and wind at the initial time of LMV

(a)12 June 2004, (b)21 July 1998, (c)29 June 1999 (the thick solid line represents the trough, "D" rep resents the center of LMV)

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图 6 MV生成阶段天气形势合成分析

(a)200 hPa流场 (浅色阴影区代表风速大于20 m/ s区域, 深色阴影区代表大于32m/ s急流, 圆圈代表LMV源地), (b)500 hPa高度场 (单位:gpm, 黑色实箭头代表 500 hPa急流, 黑色虚线箭头代表 850 hPa急流, 虚线代表 500 hPa槽线, 圆圈代表LMV源地), (c)850 hPa风矢量场和等风速线 (单位:m/ s, 圆圈代表LMV源地), (d) 地面气压场 (实线, 单位:hPa) 和温度场 (单位:K, 浅色阴影区为大于297 K暖区, 深色阴影区为大于298 K暖区)

Fig. 6 Compo sites of synoptic charts at the initial time of LMV

(a) stream fields at 200 hPa (wind speed greater than 20 m/s is shaded with light grey, wind speed greater than 32 m/s is shaded with dark grey; the dark circle indicat es the initial location of LMV), (b) geopo tential height fields at 500 hPa (unit :gpm, dark solid arrow represent sas jet location at 500 hPa, dark dashed arrow rep resent sas jet at 850 hPa, and dashed line indicatest rough at 500 hPa; the dark circle indicates the initial location of LM V), (c) wind vector and isotach ana lysis at 850 hPa (unit :m/s; the dark circle indicates the initiall ocation of LMV), (d) surface pressure analysis (unit:hPa) and temperature (unit:K, temperatu regreater than 297 Kis denoted by light shaded, and temperatu regreater than 298 Kis denoted by darks haded)

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表 1 1998-2005年长江下游LMV过程

Table 1 L ist of LMV in the lower reaches of the Yangtze during 1998-2005

表 2 LMV新生阶段物理量指数特征值

Table 2 Typical values of physical factors at initial stage of LMV

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