Weather regimes and their connection to the winter rainfall in Portugal
Weather regimes and their connection to the winter rainfall in Portugal
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天气状况及其与葡萄牙冬季降雨的关系
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
S. Leite
中科院分区：
文献类型：
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作者：
J. Santos;J. Corte;S. Leite
葡萄牙的冬季降雨与欧洲-大西洋区域的大尺度大气流动密切相关。对日平均海平面压力场的经验正交函数子集所跨越的空间进行K均值聚类分析，旨在分离导致冬季降水年际变化的天气状况。每个日环流型态都与五种天气型态（C、W、NAO−、NAO+和E）有关。每个区域的动态结构证实了各自降雨分布的统计特性，并验证了聚类技术。C型与北大西洋上空的低压系统有关，该系统在该国上空诱发了西南风和西风湿风。W区以西风扰动天气为特征，并伴有主要位于北欧的低压系统。NAO -状态表现为葡萄牙附近的弱低压系统。NAO+状态对应于一个发育良好的亚速尔高原，气候条件普遍沉降和干燥。最后，E状态与异常的强东风和相当干燥的条件有关。尽管C和NAO -模式发生频率的变化在整个葡萄牙冬季降雨的年际变化中占主导地位，但C模式在葡萄牙北部特别有意义，而NAO -模式在葡萄牙南部具有更高的相关性。W型体系的加入改善了对葡萄牙北部和中部变异性的描述。干燥的天气条件在NAO+和E模式中普遍存在，几乎没有任何例外。NAO+和NAO -状态的发生也与北大西洋涛动密切相关。版权所有©2005英国皇家气象学会
Wintertime rainfall over Portugal is strongly coupled with the large‐scale atmospheric flow in the Euro‐Atlantic sector. A K‐means cluster analysis, on the space spanned by a subset of the empirical orthogonal functions of the daily mean sea‐level pressure fields, is performed aiming to isolate the weather regimes responsible for the interannual variability of the winter precipitation. Each daily circulation pattern is keyed to a set of five weather regimes (C, W, NAO−, NAO+ and E). The dynamical structure of each regime substantiates the statistical properties of the respective rainfall distribution and validates the clustering technique. The C regime is related to low‐pressure systems over the North Atlantic that induce southwesterly and westerly moist winds over the country. The W regime is characterized by westerly disturbed weather associated with low‐pressure systems mainly located over northern Europe. The NAO− regime is manifested by weak low‐pressure systems near Portugal. The NAO+ regime corresponds to a well‐developed Azores high with generally settled and dry weather conditions. Finally, the E regime is related to anomalous strong easterly winds and rather dry conditions. Although the variability in the frequencies of occurrence of the C and NAO− regimes is largely dominant in the interannual variability of the winter rainfall throughout Portugal, the C regime is particularly meaningful over northern Portugal and the NAO− regime acquires higher relevance over southern Portugal. The inclusion of the W regime improves the description of the variability over northern and central Portugal. Dry weather conditions prevail in both the NAO+ and E regimes, with hardly any exceptions. The occurrence of the NAO+ and the NAO− regimes is also strongly coupled with the North Atlantic oscillation. Copyright © 2005 Royal Meteorological Society