1. Analysis for the Structure of Meso-scale Convective Systems on Squall Line Process on July 12 2004 at Shanghai Liu shuyuan Sun Jian ( CAMS, Beijing, China ) Yang yinming (Shanhai Meteorological Center )

2. Objective Many good work about SL and bow echo have been done by Meteorological scientist. The sketch map has been put forward by the COMET program. Most of the cases which have been analyzed were occurred outside of China. The meso-scale structure hadn’t been analyzed in china before the Doppler radar network was established. The structure of the squall line and bow echo occurred at different area maybe not same because of the different climate and terrain.

3. Outline Synoptic view of the weather at July 12 th 2004 Analysis based on the infrared image Retrieved, verified and analysis of the horizontal wind field and reflectivity Conclusion

4. Synoptic overview of the weather at JULY 12 th 2004

5. Precipitation 28.4mm ; temperature went down 10 0 ; the biggest instantaneous Wind gust up to 29m/s. during this process (local time) Make severe disaster instantaneous temperature the squall line process was happened during 1700 to 1900 July 12th 2004, moved rapidly across Shanghai

6. potential height, temperarure and wind vector: (a)500hPa and (b) 850hPa at 2000 June 12 th Shanghai was located in the front of a cold front, the Low-level southwest jet above shanghai. shandong-anhui-henan-hubei-hunan low eddy This situation is favorable to the squall line ‘ s occurring

7. instantaneous wind( automatic-observing station)

8. instantaneous wind

13. Analysis based on the infrared image

14. B C A A 7 月 12 日 16:25 17:01 July 12th 7 月 12 日 16:25 16:25 July 12th Cloud band of cold front Some MCSs in the front the cloud band The time interval of the infrared image is about half an hour

15. A B C 17:25 July 12th developed very quickly. A and B moved toward east, C moved toward northwest.

16. C A D 18:13 July 12th B these three MCSs did not form a line, one of them was located the place opposites the others. The strong wind shear line was located in the interspaces of three MCSs 。 D-----new

17. Retrieved, tested and analysis of the horizontal wind field

18. The data Shanghai Doppler radar ： altitude 0.58 km ； A volume scan per 6,9 elevation ， azimuth resolution 1 0 ， radial resolution 0.25 km,range 233 km Because of the data at high elevation is bad, the low elevation data be used only(100*sin0.48 =83.77m ).

19. Retrieved method VAP （ Velocity Azimuth Processing ） (put forward by Tao Zuyu 1992) Vr >0 toward radar ， Vr <0 away from radar ， α is the angle between the radial velocity and wind vector ， θ is azimuth. Horizontal wind speed Horizontal wind direction

20. Tangent radius （ km ） θ（0）θ（0）（ km ） <10 10~20 >20 125 7 6 6~2 2 2.4(10) 4.1(20) 6 8.7 radial resolution is 0.25km resolution of the retrieved wind field

21. Verifying

22. （a）（a） upright Character : zero line---Upright, positive—toward Negative—away from corresponding with cyclone

23. （a）（a） compared with the instantaneous wind

24. radar

25. Analysis

26. Analysis based on the reflectivity observed by Doppler radar

27. Three strong reflectivity region Two weak narrow echo band 17:31 July 12th Elevation 0.48

28. BOW The weak echo line at the front of the squall line disappeared The moving speed about 60km/hour during 1731 to 1800 18:00 July 12th Elevation 0.48

29. The moving speed about 45km/hour during 1800 to 1829 Squall line began to weaken 18 ： 29 July 12 2004

30. A B C A B C According to the location The strong reflectivity range correspond with three MCSs 31.001  N ， 121.885  E ） infrared nephogram at 1725 July 12 2004

31. Analysis on horizontal wind field

32. Three cyclones Southeast----northwest and southwest and northeast--- southwest and The wind convergence about line1 line2

33. Here were Northwest wind and Southwest at rear of squall line front Southeast wind at the front of squall line front. cyclone and anticyclone

34. Two Dimensional Sketch map of series multiple squall line maturedeveloping

35. Conclusion 1)This squall line process was mainly caused by three MCSs located in the front of cold front. But these three MCSs did not form a line, one of them was located the place opposites the others. The strong wind shear line was located in the interspaces of three MCSs 。 2)The analysis on reflectivity show that the appearance of weak narrow-echo-band indicates the squall line system will strengthen, it’s disappearance indicates squall line system will weaken. 3) two wind shear lines were found according to two reflectivity lines. The convergence wind field about line1and line2 was manifest. The convergence about line1 was formed by Southeast wind and Southwest wind,and the line2 was squall line front. Here were Northwest wind at rear of squall line front and Southeast and Southwest wind at the front of squall line front. There were cyclone and anticyclone apparent on the northern and southern ends of this line and meso-lows in the front of bow echoes. 4)Include two independent structure-----two bow echo,

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