Role of storm track activity in the interannual seesaw of summer precipitation over northern Eurasia
Role of storm track activity in the interannual seesaw of summer precipitation over northern Eurasia
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DOI：
10.1029/2003jd003912
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发表时间：
2004-01
影响因子：
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通讯作者：
Y. Fukutomi;K. Masuda;T. Yasunari
中科院分区：
文献类型：
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作者：
Y. Fukutomi;K. Masuda;T. Yasunari
[1]在相对干湿极端之间的振荡是西伯利亚夏季降水年际变化的一个显著特征。最近，我们发现东西伯利亚和西西伯利亚（ES和WS）流域尺度降水的时间特征存在非相位关系。这种东西向的跷跷板在过去30年里表现得尤为明显。与这种东西跷跷板相关的大尺度降水和环流异常的空间结构以横跨欧亚大陆北部的东西偶极子为特征。研究了1972-2001年6 - 8月北方夏季降水偶极子型和大尺度环流异常的重要大气过程。特别地，本工作侧重于与天气尺度（<10天）涡旋相关的风暴路径活动在产生与降水异常偶极子对应的静止波中的作用。对西伯利亚夏季降水跷跷板的两个极端进行了线性回归和各种涡统计的综合分析。这两个极端阶段分别表示为ES-wet-WS-dry和WS-wet-ES-dry。与降水跷跷板相关的夏季平均大气异常与降水偶极子异常同时呈现平稳波列型。冷槽/暖脊偶极子对应相对干湿区。对风暴路径活动的分析揭示了类似的东西对比结构，这意味着与异常风暴路径相关的位移伴随着两个极端阶段之间的相位反转。一个异常静止槽（脊）对应于ES和WS的异常高（低）天气尺度涡旋活动区。研究了天气尺度涡旋的强迫，以证实欧亚驻波上的风暴路径反馈。结果表明，天气尺度涡度通量诱导的正压反馈与欧亚波场是同相的。气旋（反气旋）环流强迫与异常静止槽（脊）同时存在。这些空间相干关系表明，涡旋通量引起的风暴路径反馈有助于加强和维持欧亚波结构以及各相降水偶极子型。因此，欧亚风暴路径强度和位置的年际变化是影响两个极端阶段之间平均降水和环流模式的关键因素。
[1] Oscillation between relatively dry and wet extremes is a noteworthy characteristic of the interannual variability in summer precipitation over Siberia. Recently, we identified an out-of-phase relationship in the temporal signature of basin-scale precipitation between eastern and western Siberia (ES and WS). This east-west seesaw has been especially pronounced during the past 30 years. The spatial structure of large-scale precipitation and circulation anomalies associated with this east-west seesaw is characterized by an east-west dipole across northern Eurasia. We extended our work to investigate the important atmospheric processes involved in the dipole patterns of precipitation and large-scale circulation anomalies for the northern summers (June–August) of 1972–2001. In particular, this work focuses on the role of storm track activities associated with synoptic-scale (<10 days) eddies in producing the stationary waves that correspond to the precipitation anomaly dipoles. Linear regression and composite analyses of various eddy statistics are performed for two contrasting extremes in the Siberian summer precipitation seesaw. These two extreme phases are denoted ES-wet-WS-dry and WS-wet-ES-dry. The summer mean atmospheric anomalies related to the precipitation seesaw show stationary wavetrain patterns in conjunction with the precipitation dipole anomalies. The cold trough/warm ridge dipole corresponds to the relative wet and dry region. Analysis of storm track activity reveals similar east-west contrasting structures, meaning that the displacements associated with the anomalous storm tracks are accompanied by a phase reversal between the two extreme phases. An anomalous stationary trough (ridge) corresponds to the anomalous high-(low-)synoptic-scale-eddy-activity region in both ES and WS. The forcing by synoptic-scale eddies is examined to confirm the storm track feedback on the Eurasian stationary waves. The results show that barotropic feedback induced by synoptic-scale eddy vorticity fluxes is in phase with the Eurasian wave field. Cyclonic (anticyclonic) circulation forcing is collocated with the anomalous stationary trough (ridge). These spatially coherent relationships suggest that storm track feedback due to eddy vorticity fluxes helps to reinforce and maintain the Eurasian wave structure coupled with the precipitation dipole pattern of each phase. Consequently, the interannual variability of the Eurasian storm track intensity and location is a crucial factor in forcing the mean precipitation and circulation patterns between the two extreme phases.