Contrasting Mechanisms of Summer Blocking Over Western Eurasia
Contrasting Mechanisms of Summer Blocking Over Western Eurasia
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DOI：
10.1029/2018gl079894
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发表时间：
2018-11-16
影响因子：
5.2
通讯作者：
Woollings, Tim
中科院分区：
文献类型：
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作者：
Drouard, Marie;Woollings, Tim
夏季阻塞事件的形成似乎主要是研究了几个单独的事件往往与热浪。在这里，我们调查夏季阻塞事件的动力学在欧亚大陆西部的三个地区，以得出一些更一般的结论，主要是在高频和低频过程。二维阻塞事件检测算法应用于1958-2017年期间ERA-40和ERA中期再分析的500 hPa位势场。结果表明，高，低频率的过程是重要的启动阻塞事件在欧洲中南部。在俄罗斯西部的阻塞事件之前，一个显着的低频大规模波列，其形成和维持的低频过程只占主导地位。最后，它表明，极端季节，如2010年夏季的风险不能准确地估计从泊松统计过去events.Plain语言摘要大气阻塞事件对应于一个大规模的逆转的纬向压力梯度，阻止向东传播的急流。在大气压图中，它们的特点是大规模的高压系统。阻塞事件强烈影响天气，主要是因为它们的持续性（长达4-5周），这使得温度异常放大。由于它们的长期持续性，它们在夏季可能与热浪有关，这会产生重大的社会影响（如1976年6月在英国，2003年8月在法国，或2010年7月至8月在东欧和俄罗斯）。阻塞事件的动力学研究在夏季比在冬季少，部分原因是在夏季阻塞事件的发生较少。在这里，我们解决的动力学过程中涉及的欧洲-俄罗斯西部地区（1976年，2003年和2010年阻塞事件发生），以更好地了解他们的形成和动力学的关键成分是什么。为了做到这一点，我们在欧洲-俄罗斯西部地区的三个关键地区观察了夏季的阻塞事件。我们表明，俄罗斯西部是特别容易非常长，高影响块由于大气流体动力学的性质，影响该地区。
The formation of summer blocking events appears to have been mostly studied for a few individual events often associated with heat waves. Here we investigate summer blocking event dynamics in three areas over western Eurasia in order to draw some more general conclusions, mostly in terms of high- and low-frequency processes. A 2-D blocking event detection algorithm is applied to the 500-hPa-geopotential field from the ERA-40 and ERA-Interim reanalyses over the 1958-2017 period. It is shown that both high- and low-frequency processes are important to initiate blocking events over southern central Europe. Blocking events over western Russia are preceded by a significant low-frequency large-scale wave train, and their formation and maintenance are dominated by low-frequency processes only. Finally, it is shown that the risk of extreme seasons such as summer 2010 cannot be accurately estimated from the Poisson statistics of past events.Plain Language Summary Atmospheric blocking events correspond to a large-scale reversal of the meridional pressure gradients that blocks the eastward propagating jet stream. In an atmospheric pressure chart, they are characterized by a large-scale high-pressure system. Blocking events strongly impact the weather mainly because of their persistence (up to 4-5 weeks), which allows anomalies in temperature to amplify. Because of their long persistence, they can be associated in summer with heat waves, which have major societal impacts (as in June 1976 in the UK, August 2003 in France, or July-August 2010 over eastern Europe and Russia). Blocking events dynamics has been less studied in summer than in winter, partly because of the smaller occurrence of blocking events in summer. Here we address the dynamical processes involved in summer blocking events over the European-western Russia region (where the 1976,2003, and 2010 blocking events occurred) to better understand what the key ingredients for their formation and dynamics are. To do that, we looked at blocking events in observations in summer over three key areas in the European-western Russia area. We show that western Russia is particularly prone to very long, high-impact blocks due to the nature of the atmospheric fluid dynamics that influences that region.