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Effects of Synoptic Scale and Sub-synoptic Scale Systems on Formation of a Heavy Rainfall Process
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摘要: 采用中尺度数值模式MM5V2对1998年6月下旬发生在长江流域持续的暴雨过程进行分析研究。通过尺度分离与数值模拟对比试验，着重分析了暴雨过程中天气尺度与次天气尺度各物理量场的结构特征，提出本次暴雨过程形成的物理机制：天气尺度流场与水汽场为降水提供持续的远距离水汽输送通道，次天气尺度流场形成稳定的经向强辐合，为水汽的抬升与凝结提供动力条件；在有利的高、低空急流的配置下，暴雨区落在高空急流轴以南、低空急流轴以北；次天气尺度温度场下暖上冷的热力不稳定层结促进了热力不稳定的发展，促使暴雨增幅；特大暴雨发生地区上空的次天气尺度湿度的高值中心，有利于湿空气在上升运动中释放潜热，形成暴雨的反馈机制。数值试验分离模式初始场不同尺度系统信息，揭示了不同尺度系统在暴雨发生过程中的动力作用，没有中尺度系统的配合，仅有天气尺度系统信息，或只有次天气尺度系统信息，没有大尺度系统的配合，暴雨的强度及范围都将有所消减。分析及数值试验结果表明大暴雨是在天气尺度和次天气尺度系统的共同作用下才得以产生和维持的。Abstract: By means of the mesoscale numerical model MM5V2, the heavy rainfall process during the later June of 1998 in the middle and lower reaches of the Yangtze River is analyzed. By utilizing the scale-separating method and comparing the results of numerical experiments, the characteristics of physical elements of synoptic scale and sub-synoptic scale systems are investigated. The physical mechanisms of heavy rainfall formation are presented as follows: synoptic scale wind and water vapor fields provided long-distance water vapor transportation for the heavy rainfall while the sub-synoptic scale wind field results in strong meridional convergence which provided the steady dynamic condition for the lifting and condensation of water vapor; under the favorable disposition of upper and low level jets, the rainfall region was located to south of the upper level jet and north of the low level jet; the unstable thermal stratification, cooler at lower level and warmer at upper level, of the sub-synoptic scale temperature field facilitated the development of the thermal unstable condition and further strengthened the heavy rainfall; the sub-synoptic scale high-value center of the specific humidity field over the rainfall area was favorable to the emission of latent heat and further enhanced the feedback mechanism of the heavy rainfall. In numerical experiments, message separation was conducted on the systems with different scales in the model initial field to indicate their dynamic effects in the heavy rainfall process. The results show that both intensity and coverage of heavy rainfall will decrease to some extent while there is only a synoptic scale or sub-synoptic scale system during rainfall process. Analyses and results of numerical experiments suggest that heavy rainfall can form and sustain under the comprehensive effects of both synoptic scale and sub-synoptic scale systems.
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Key words:
- Heavy rain;
- Synoptic scale;
- Sub-synoptic scale
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图 9 6月23~26日12:00UTC平均700 hPa水汽通量q V（单位：m·s -1·g·kg-1）和比湿（单位：g·kg-1）
(a) 原场 (b) 天气尺度场（c）次天气尺度场
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[1] 陶诗言.有关暴雨分析预报的一些问题.大气科学, 1977, 1(1):64-72. http://www.cnki.com.cn/Article/CJFDTOTAL-DQXK197701009.htm [2] 丁一汇, 蔡则怡, 李吉顺. 1975年8月上旬河南特大暴雨的研究.大气科学, 1978, 2(3):276-289. http://www.cnki.com.cn/Article/CJFDTOTAL-DQXK197804001.htm [3] 夏大庆, 郑良杰.大尺度环境场中中尺度对流系统生成的数值摸拟试验.大气科学, 1987, 11(2):185-193. http://www.cnki.com.cn/Article/CJFDTOTAL-DQXK198702009.htm [4] 何齐强, 陈永胜, 崔志强.两次局地短生命的强对流天气过程的分析.空军气象学院学报, 1994, 15(4):332-339. [5] 徐祥德.天气尺度系统稳定性结构、相路特征的分岔及热源时间振荡影响问题的探讨.气象学报, 1987, 45(2):141-149. http://www.cnki.com.cn/Article/CJFDTOTAL-QXXB198702002.htm [6] 徐祥德.暴雨过程汇合流场不同尺度系统相互影响效应的初步研究.南京气象学院学报, 1987, 10(2):226-234. http://www.cnki.com.cn/Article/CJFDTOTAL-NJQX198702012.htm [7] 国家气象中心、国家卫星气象中心. '98中国大洪水与天气预报.北京:气象出版社, 1998. [8] 中国气象局国家气候中心. '98中国大洪水与气候异常.北京:气象出版社, 1998. [9] Shapiro R. Smoothing filtering and boundary effects. Review of Geophysics and Space Physics, 1970, 8: 359-387. doi: 10.1029/RG008i002p00359 [10] 张玉玲, 吴辉碇, 王晓林.数值天气预报.北京:科学出版社, 1987. [11] 陈受钧, 谢安.次天气尺度与天气尺度系统间动能交换的诊断分析.气象学报, 1981, 39(4):408-415. http://www.cnki.com.cn/Article/CJFDTOTAL-QXXB198104002.htm [12] 魏凤英, 朱福康.一种分离暴雨过程天气尺度和次天气尺度特征的方法.大气科学, 2003, 27(2):191-202. http://www.cnki.com.cn/Article/CJFDTOTAL-DQXK200302005.htm [13] 寿绍文.中尺度天气动力学.北京:气象出版社, 1993. -
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