Hydrological extremes in the Aksu-Tarim River Basin: Mid-latitude dynamics
Hydrological extremes in the Aksu-Tarim River Basin: Mid-latitude dynamics
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阿克苏-塔里木河流域极端水文：中纬度动态
DOI：
10.1007/s00382-015-2650-x
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发表时间：
2016-04
期刊：
影响因子：
4.6
通讯作者：
H. Borth;H. Tao;K. Fraedrich;A. Schneidereit;Xiuhua Zhu
中科院分区：
文献类型：
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作者：
H. Borth;H. Tao;K. Fraedrich;A. Schneidereit;Xiuhua Zhu
对塔里木河流域39个气象站1961-2010年降水资料的分析表明，塔里木河流域极端湿事件的增多，使塔里木河流域的降水呈现出由干向湿的变化趋势。第一阶段（1961-1986年）和第二阶段（1987-2010年）是对变化中的干旱和潮湿极端情况进行动力学分析的基础，这些极端情况与欧洲大陆上空的气旋活动和北方中纬度地区的环流异常密切相关。对丰水月和枯水月的波列、气旋路径、水汽通量和位涡锋分析表明：（1）塔里木河流域上游冬、夏季极端丰水和枯水的波列型特征明显;所有波列起源于南极洲-欧洲部门，指向波列动力学作为观察到的连接模式的一种可能机制。(2)所选的极端个例表明，即使气旋路径从未穿过塔里木盆地，异常降水事件也可能与对流层上部的特征气旋路径和PV锋有关。极端潮湿的冬季的特点是气旋路径靠近塔里木盆地的西部和北方边界，而在极端干燥的冬季，这样的气旋路径是不存在的。多雨的夏季以塔里木河流域西北角的长期气旋异常为特征[另见（3）]。在干燥的夏季，这种异常现象是不存在的。(3)在更局部的水平上，水文极端事件与对流层上部PV锋的特殊动力结构有关。在冬季，强降水（极端）与塔里木河流域的强非线性波发展或破波事件有关。随着非线性波的发展，水汽和降水区向塔里木河流域平流输送。在干燥的冬季，对流层上层PV锋更加纬向，波浪破碎的频率较低。在极其潮湿的夏季，强降水事件与强破坏事件以及塔里木河流域上空或以北长寿命几乎静止的气旋的形成有关。
Analyses of precipitation (1961–2010) from 39 meteorological stations in the Tarim River Basin revealed a trend from dryer towards wetter conditions induced by an increase of the number of wet extremes. A first (1961–1986) and second (1987–2010) period are the basis for a dynamical analysis of changing drought and wetness extremes which are closely related to cyclonic activity over the European continent and circulation anomalies in the Northern Hemisphere mid-latitudes. Wave train, cyclone tracks, water flux and potential vorticity (PV) front analysis of the wet and dry months show the following result: (1) The extreme wet and dry cases in winter and summer are characterized by distinguished wave train patterns upstream of the Tarim River Basin. All wave trains originate in the Atlantic–European sector pointing towards wave train dynamics as one possible mechanism underlying the connection patterns observed. (2) The selected extreme cases show that exceptional precipitation events can be connected to characteristic cyclone tracks and a PV front in the upper troposphere even if cyclone tracks never cross the Tarim Basin. Extremely wet winters are characterized by cyclone tracks close to the western and northern boundary of the Tarim Basin whereas, during extremely dry winters, such cyclone tracks are absent. Wet summers are characterized by long-lived cyclonic anomalies at the north western corner of the Tarim River Basin [see also (3)]. During dry summers such anomalies are absent. (3) On a more local level the hydrological extreme events are linked to special dynamical structures of the upper tropospheric PV front. In winter strong (extreme) precipitation is connected to a strong non-linear wave development or a wave-breaking event over the Tarim River Basin. Together with non-linear wave development moisture and precipitation areas are advected towards the Tarim River Basin. In dry winters the upper tropospheric PV front is much more zonally oriented and wave-breaking is less frequent. Strong precipitation events are connected to strong breaking events and to the formation of long-lived nearly stationary cyclones over or north of the Tarim River Basin during extremely wet summer months.