Atmospheric circulation patterns related to heavy snowfall days in Andorra, Pyrenees
Atmospheric circulation patterns related to heavy snowfall days in Andorra, Pyrenees
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DOI：
10.1002/joc.1103
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发表时间：
2005-03-15
期刊：
影响因子：
--
通讯作者：
Mases, M
中科院分区：
文献类型：
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作者：
Esteban, P;Jones, PD;Mases, M
山区的大雪往往是引发雪崩的直接原因。特定的天气尺度大气状况是造成此类极端降雪事件的原因，安道尔（法国和西班牙之间的比利牛斯山脉小国）的情况确实如此。基于 24 小时内积雪强度至少为 30 厘米的日子，本研究使用主成分分析 (PCA) 和聚类技术来表征冬季这些日子的天气环流模式。分析区域涵盖北纬 30-60 度、西经 30 度-东经 15 度的区域，期间涵盖 1986-87 年至 2000-01 年的冬季。所提出的方法涉及一种预处理方法，包括用于 PCA 的数据的空间标准化、用于确定 K 均值聚类的质心和组数的替代近似，以及拒绝该算法的迭代。这种方法能够对每个大雪天进行天气分类，并构建了海平面气压、500 hPa 位势高度和 1000-500 m 厚度（5270 m、5400 m 和 5520 m 等高线）的合成图。结果显示了七种环流模式，其中大多数具有大西洋风的成分，其他则具有明显的地中海平流，可能与寒冷的大陆空气结合。结果作为天气图，可以成为辅助气象模型进行大雪预报的有用工具，并且所获得的当天的分类为未来对已建立的类型进行详细的气象和气候分析提供了可能性。版权所有 (c) 2005 英国皇家气象学会。
Heavy snowfalls over mountain regions are often a direct cause of avalanches. Specific synoptic-scale atmospheric situations are responsible for these kinds of extreme snowfall event, and this is indeed the case for Andorra, a small country located in the Pyrenees, between France and Spain. Based on days with an intensity of at least 30 cm of snow in a 24 h period, the present study uses principal component analysis (PCA) and clustering techniques to characterize the synoptic circulation patterns for these days during the winter season. The area of analysis encompasses the region 30-60 degrees N by 30 degrees W-15 degrees E and the period covers the winter seasons from 1986-87 to 2000-01. The methodology proposed involves a preprocessing approach consisting of a spatial standardization of the data used for the PCA, an alternative approximation to decide the centroids and the number of groups for the K-means clustering, and the rejection of the iterations for this algorithm. This approach enables the synoptic classification of every heavy snowfall day, and composite maps were constructed for sea-level pressure, 500 hPa geopotential height, and 1000-500 m thickness (the 5270 m, 5400 m and 5520 m contour lines). The results show seven circulation patterns, most of them with an Atlantic component of the wind, and others with a clear Mediterranean advection that could be combined with cold continental air. The results, as weather charts, could be a useful tool to assist meteorological models in heavy snowfall forecasting, and the day's classification obtained opens up future possibilities for detailed meteorological and climatological analysis of the established types. Copyright (c) 2005 Royal Meteorological Society.