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基于1981~2012年长江上游128个中小洪水历史个例及NCEP/NCAR再分析资料,采用普查及天气学分型方法,建立了纬向型、经向型、偏东气流型以及两高之间型4种致洪降水天气学概念模型,研究了各天气型致洪降水发生机理及相应中小洪水特征。得到以下结论:纬向型中高纬环流相对平直多波动,伴有明显冷平流南下,地面锋面位置略偏北。该类型强降水过程多,强度大,持续时间长,对应中小洪水多为双峰或多峰型,平均洪峰流量、过程增幅最强,洪水过程时间也最长。经向型环流中高纬贝加尔湖和东北地区为深厚低槽,中低层常伴有暖式切变线或低涡发展,中上层急流出口处的辐散以及冷平流四类型中最强。该类型雨带多呈东北-西南走向,中小洪水一般以单峰为主,其洪峰流量及过程增幅均较大,造成的洪水涨水较快,过程时间最短。纬向和经向型均为全流域降水型,但在金沙江北部、岷沱江、嘉陵江以及宜宾-宜昌常出现较高频次的60 mm以上较强面雨量。偏东气流型副高与热带气旋外围环流汇合北进,其强降水前后冷暖平流变化不明显,受地形强迫抬升影响,最易产生准静止型、团状、突发性强降水。该类型中小洪水以单峰为主,涨水快,洪峰流量及过程增幅均最小,强降水主要分布在嘉陵江和岷沱江两大流域。两高之间型多为“鞍”型场的环流配置,青藏高压与副高在流域上空形成南北向切变线,其动力和水汽条件均较弱。该类型降水强度较弱,稳定少动,累积降水量较大,洪水以单峰为主,双峰偶有发生,其洪峰流量、过程增幅均较大,洪水过程时间较长,强降水多位于岷沱江、嘉陵江和宜宾-重庆中部流域。
Based on the historical records of 128 small and medium floods in the upper reaches of the Yangtze River from 1981 to 2012 and the NCEP / NCAR reanalysis data, a general survey and a weather classification method were used to establish the zonal, meridional, Four kinds of conceptual models of flood precipitation weather are studied, and the mechanism of flood precipitation caused by each weather type and the characteristics of corresponding small and medium floods are studied. The following conclusions are drawn: the latitudinal mid-high latitudes circulation is relatively straight and more fluctuating, accompanied by obviously cold advection southward, and the frontal surface location is slightly northward. This type of heavy precipitation process, strength, long duration, mostly corresponding to small and medium-sized flood peak or bimodal type, the average peak flow, the strongest process of increase, the longest flood process. The meridional circulation in the high latitude Baikal Lake and the northeastern region are deep and low troughs. The middle and lower layers are often accompanied by the development of the thermal shear line or vortex. The divergence at the middle and upper jet exits and the strongest in the four types of cold advection. This type of rain belt mostly northeast - southwest, small and medium-sized flood generally single-peak-based, its peak flow and process increases are larger, resulting in flood water faster, the shortest process time. Both latitudinal and meridional types are all rainfall patterns in the whole basin. However, in the northern part of Jinsha River, more frequent rainfalls of 60 mm and above occur frequently in the Minato Tuo River, Jialing River and Yibin-Yichang. The subtropical high and the peripheral circulation of the tropical cyclone converge northward, and there is no obvious change in the cool-warm advection before and after the heavy rainfall. Affected by the forcibly uplifting of the terrain, it is most likely to produce quasi-static type, slug-like and sudden heavy rainfall. This kind of small and medium-sized flood mainly takes the single peak as the main one, the flood rising fast, the flood peak flow and the process increasing are smallest, the heavy rainfall is mainly distributed in Jialing River and Min Tuojiang two rivers. Mostly between the two high-altitude “saddle” type of field circulation configuration, the Qinghai-Tibet high pressure and subtropical high over the watershed to form a north-south shear line, the power and water vapor conditions are weak. This type of precipitation intensity is weak, stable and less dynamic, the cumulative precipitation is larger, the flood is mainly single peak, double peaks occur occasionally, the flood peak flow, the process of amplification are larger, the flood process takes longer, Min Tuojiang River, Jialing River and Yibin - the central part of Chongqing.