新疆地区一次对流性降水的三维中尺度风场研究

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庄薇, 刘黎平, 王楠. 新疆地区一次对流性降水的三维中尺度风场研究[J]. 应用气象学报, 2006, 17(4): 444-451. 复制到剪切板

Zhuang Wei, Liu Liping, Wang Nan. Study on Three-dimensional Wind Fields of Mesoscale Convective Systems in Xinjiang[J]. Journal of Applied Meteorological Science, 2006, 17(4): 444-451 复制到剪切板

新疆地区一次对流性降水的三维中尺度风场研究

庄薇¹, 刘黎平¹, 王楠²

1. 中国气象科学研究院灾害天气国家重点实验室, 北京 100081;
2. 陕西省气象台, 西安 710015

2005-07-15 收到, 2006-02-16 收到修改稿.

资助项目: 国家自然科学基金项目 (40375008) 资助

摘要: 利用2004年外场试验获得的乌鲁木齐和五家渠C波段双多普勒雷达资料, 分析了双多普勒雷达风场反演方法和资料的可靠性, 研究了2004年8月8日发生在乌鲁木齐和五家渠的一次强对流性降水的回波和风场中尺度结构及演变过程。结果表明:这两部雷达观测的回波强度相关很好, 雷达基线上的径向速度基本一致, 资料可靠, 适合进行双多普勒雷达观测; Cressman插值的影响半径的变化对风场的中尺度结构基本没有影响, 径向速度误差引起的风场反演误差与该点所处的位置有关, 1 m/s径向速度误差也不会改变风场的中尺度结构。该过程为对流单体发展为对流带状回波的过程, 在对流单体的左侧生成新的对流单体, 逐步发展为长度约90 km范围的带状对流系统, 该系统恰与较强的东北风和较弱的西风形成的辐合相对应, 上升气流与强对流回波相对应, 不同对流单体有各自相独立的风场结构。用双多普勒雷达观测得到对流系统的内部风场有利于了解对流系统的内部动力过程, 从而探讨降水的形成和演变机理。

关键词: 双多普勒雷达风场结构中尺度对流系统

Study on Three-dimensional Wind Fields of Mesoscale Convective Systems in Xinjiang

Zhuang Wei¹, Liu Liping¹, Wang Nan²

1. State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081;
2. Shaanxi Meteorological Observatory, Xi'an 710015

Abstract: The dual Doppler radar system constructed by two C-band Doppler radars in Urumqi and Wujiaqu is used to detect convective systems in Xinjiang Uighur Autonomous Region in 2004, it is supported by the project of National Natural Science Foundation of China (NSFC) "Study on Meso-scale Kinetic and Thermodynamic Feature of Precipitation System with Dual Doppler Radar in Xinjiang". It focuses on the three-dimensional wind field retrieved with dual Doppler radar technique in the strong mesoscale convective systems that produces relatively heavy rainfall within the observational network from 22:30 (BT) 7 August to 02:30 8 August 2004, and the three-dimensional wind structure of these systems as well as their evolution processes are analyzed. Moreover, the radar data quality and reliability of the wind retrieval algorithm with dual Doppler radar are also examined. The positions and structures of radar echoes captured by the two radars are well matched, the radial velocities observed by the radars above the radar baseline are mostly the same, the dual Doppler radar technique is reliable and suitable for the observations of mesoscale convective systems. The sensitivity analysis of the interpolation algorithm on wind retrieval framework demonstrates that the influence radius of Cressman interpolation does not play a significant role in determining the wind structures of mesoscale convections. Even though the wind retrieval errors resulted from the radial velocity measurement errors are associated with their relative positions to the radars, however, such type of errors within 1 m/s on redial velocity would not change the major shapes of the mesoscale wind structures. According to the evolutions of these mesoscale systems, the several convective cells develop into convective precipitation band. Some new cells are generated along the left side of the old ones, whose reflectivity vary from 50 to 55 dBz with the maximum 8 km top height, and finally develop as a band-shaped convective cluster (with 90 km length) after 4 hours. The convective band is corresponding with a strong convergence produced by a branch of strong northeasterly wind and a weak westerly wind, and the updraft is just located at the maximum reflectivity center. The different convective cells actually have their independent wind structures respectively, but they would subsequently interact with each other to engender heavy rainfall weathers. Besides, there are limits to the measurements on this type of mesoscale convective systems in the conventional observations, such as radio sounding, whose spatial and temporal resolutions are limited at hundreds kilometers and 12 hours respectively. Consequently, it is not sufficient to determine their dynamic structures, which develop quickly and have relatively short lifecycle. Fortunately, due to the retrieved wind fields of these mesoscale convections with dual Doppler radar observations, it would be easier to analyze their kinetic features and therefore study the initiation and development mechanism of the mesoscale rainfall systems.

Key words: dual Doppler radar wind structure mesoscale convective system

[1]	Armijo L. A theory for the determination of wind and precipitation velocities with Doppler radar. J Atmos Sci, 1969, 26, (3): 570–573. DOI:10.1175/1520-0469(1969)026<0570:ATFTDO>2.0.CO;2
[2]	Lhermitte R M, Miller L J. Doppler Radar Methodology for the Observation of Convection Storms. 14^th Radar Meteorology Conference. American, Tucson:American Meteor Society, 1970:133-138.
[3]	Ray P S, Zieler C L, Bumgarner W. Single and multipler Doppler radar observations of tornadic storms. Mon Wea Rev, 1980, 108, (10): 1607–1625. DOI:10.1175/1520-0493(1980)108<1607:SAMDRO>2.0.CO;2
[4]	Chong M, Campos C. Extended overdetermined dual-Doppler formalism in synthesizing air-born Doppler radar data. J Atmos Oceanic Tech, 1996, 13, (3): 581–597. DOI:10.1175/1520-0426(1996)013<0581:EODDFI>2.0.CO;2
[5]	Bousquet O, Chong M. A multiple-Doppler synthesis and continuity adjustment technique to recover wind components from Doppler radar measurement. J Atmos Oceanic Tech, 1998, 15, (13): 343–359.
[6]	张沛源, 周海光, 胡绍萍. 双多普勒天气雷达风场探测的可靠性研究. 应用气象学报, 2002, 13, (4): 485–495.
[7]	刘黎平, 张沛源, 梁海河, 等. 双多普勒雷达风场误差和资料的质量控制. 应用气象学报, 2003, 14, (1): 17–29.
[8]	Ge Wenzhong, Zhang Weiping, Dang Renqing. A Study on the Non-uniform Structure of Meiyu Front Precipitation by Use of Radar Field Data, The Third GAME-HUBEX Workshop on Meso-scale Systems in Meiyu/Baiyu Front and Its Hydrological Cycle, Kunming, 2001:50-53.
[9]	周海光, 王玉彬. 双多普勒雷达对淮河流域特大暴雨的风场反演. 气象, 2002, 30, (2): 17–20.
[10]	刘黎平, 邵爱梅, 葛润生, 等. 一次混合云暴雨过程风场中尺度结构的双多普勒雷达观测研究. 大气科学, 2004, 28, (2): 278–283.
[11]	刘黎平. 用双多普勒雷达反演降水系统三维风场试验研究. 应用气象学报, 2003, 14, (4): 502–504.
[12]	Shao Aimei, Qiu Chongjian, Liu Liping. Kinematic structure of a heavy rain event from dual-Doppler radar observations. Adv Atmos Sci, 2004, 21, (4): 609–616. DOI:10.1007/BF02915728
[13]	刘黎平, 钱永甫, 王致君. 平凉地区云的雷达回波和降水的气候特征. 高原气象, 1997, 16, (3): 265–273.
[14]	伍志方, 张沛源, 张春良. 714CD多普勒天气雷达和711测雨雷达探测雷云的对比分析. 高原气象, 2000, 19, (1): 1–8.
[15]	冯建民, 徐阳春, 李凤霞, 等. 宁夏川区强对流天气雷达判别及预报指标检验. 高原气象, 2001, 20, (4): 447–452.
[16]	伍志方, 张春良, 张沛源. 一次强对流天气的多普勒特征分析. 高原气象, 2001, 20, (4): 202–207.
[17]	刘勇, 张科翔, 周丽峰, 等. 2002年陕西冰雹特点及雷达回波特征. 陕西气象, 2003, (1): 14–16.
[18]	冯锦明, 刘黎平, 王致军, 等. 青藏高原那曲地区雨季雷达回波、降水和部分热力参量的统计特征. 高原气象, 2002, 21, (4): 368–374.
[19]	梁海河, 张沛源, 葛润生. 多普勒天气雷达风场退模糊方法的研究. 应用气象学报, 2002, 13, (5): 591–601.
[20]	张沛源, 陈荣林. 多普勒速度图上的暴雨判据研究. 应用气象学报, 1995, 6, (3): 373–378.


图 1. 2004年8月8日01:50乌鲁木齐雷达在1.5 km等高面上反演的风场 (a) 影响半径为2 km, (b) 影响半径为5 km (坐标原点表示乌鲁木齐雷达的位置, 格点分辨率为1 km×1 km)


图 2. 2004年8月8日05:02在2 km等高面上乌鲁木齐与五家渠两雷达径向速度误差都为随机误差 (a) 和系统误差 (b) 时的水平风场大小的反演误差 (五家渠雷达坐标为 (13.25), 其他说明同图 1)


图 3. 2004年8月7—8日不同时刻乌鲁木齐雷达回波强度的演变过程 (仰角0.5°, 探测范围150 km, 坐标原点表示乌鲁木齐雷达的位置, 格点分辨率为1 km×1 km)


图 4. 2004年8月7—8日不同时刻乌鲁木齐雷达径向速度的演变过程 (说明同图 3)


图 5. 2004年8月8日01:50乌鲁木齐雷达在2 km等高面上水平风场 (a) 和在y=70东西剖面风场 (b) (坐标原点表示乌鲁木齐雷达的位置, (a) 和 (b) 格点分辨率分别为1 km×l km和1 km×0.5 km)