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2001年华西秋雨时空分布特点及其成因分析
SPACE-TIME DISTRIBUTION AND PHYSICAL MECHANISMS OF AUTUMN RAINS IN WEST CHINA IN 2001
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摘要: 分析了2001年华西秋雨的时空分布特点和大尺度环流背景及天气系统的主要特征, 并对秋雨形成的主要物理机制进行了诊断和分析。结果显示, 2001年秋季, 华西地区阴雨日数多, 雨区集中, 强降水时段集中在9月份。该月, 巴尔喀什湖地区500 hPa呈准稳定的低压槽, 其上不断有短波分裂东移, 携带冷空气经高原东移, 与强大的副热带高压西南侧的东南暖湿气流和来自孟加拉湾的西南暖湿气流交汇于四川盆地、陇南、陕南一带, 致使该地区持续阴雨天气。诊断分析表明, 9月, 青藏高原地区对流旺盛, 水汽凝结释放潜热, 使其成为一个强大的热源中心; 而江淮、江南一带多受西北太平洋副热带高压控制, 盛行下沉气流, 为热源低值区; 四川盆地处于高原高能量带与盆地以东低能量带之间的能量锋区。此能量锋区的存在促使从巴尔喀什湖低压槽分裂东移的短波槽在该地区发展。同时, 东路冷空气的渗入进一步加大了能量锋区的强度, 激发不稳定能量释放, 造成了四川盆地部分地区出现大暴雨甚至特大暴雨。Abstract: The space-time distribution features of autumn rains in West China in 2001, the related large-scale atmospheric circulation, and the main features of the weather systems are analyzed to study the physical mechanisms of autumn rains.The results show that there were more rainy days than normal in 2001, and the strong raining processes were concent rated around Sichuan Basin in September.The circulation analyses show that there was a quasistationary t rough near the Oz.Balchas, from which short waves were split one by one, moved southeastw ard, passed Tibet Plateau and reached the area near Sichuan Basin.Here the cold ai rs taken by the short waves were combined constantly with the warm and humid southeastair in the southeast side of the strong subtropical high and with the wet-warm south west air from the Bay of Bengal.The physical analyses show that there was a strong energy frontal zone between the high energy center in Tibet Plateau and the lowenergy center to the east of Sichuan Basin.So the short waves were developed strongly in the Basin. The intensity of the energy frontal zone was streng thened because the cold air from the east area entered so that the instability energy burst out, which triggered the rainstorm in Sichuan Basin.
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Key words:
- Autumn rain;
- Circulation feature;
- Physical mechanism;
- Energy f rontal zone
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图 3 2001年9月850hPa平均水汽通量 (矢量线, 单位:g·s-1·m-1·hPa-1) 和水汽通量散度
(虚线, 单位:10-6g.·s-1·m-2·hPa-1, 阴影区为 < -5×10-6g·s-1·m-2.·hPa-1)
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[1] 刘富明.大气环流由夏到秋的转变及其与四川秋雨形成的关系.四川气象科技, 1981, (2):1-6. [2] 任炳潭.两千年华西秋雨的初步研究.气象, 1987, 13(9):21-24. http://www.cnki.com.cn/Article/CJFDTOTAL-QXXX198709003.htm [3] 何敏.我国主要秋雨区的分布及长期预报.气象, 1984, 10(9):10-13. http://www.cnki.com.cn/Article/CJFDTOTAL-QXXX198409002.htm [4] 徐欲华等.西南气候.北京:气象出版社, 1991.45-47. -
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