Dry season circulation‐type classification applied to precipitation and temperature in the Peruvian Andes
Dry season circulation‐type classification applied to precipitation and temperature in the Peruvian Andes
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DOI：
10.1002/joc.6593
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发表时间：
2020-04
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影响因子：
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通讯作者：
Martí Bonshoms;F. Álvarez-García;J. Úbeda;W. Cabos;Kelita Quispe;G. Liguori
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文献类型：
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作者：
Martí Bonshoms;F. Álvarez-García;J. Úbeda;W. Cabos;Kelita Quispe;G. Liguori
我们首次对热带安第斯山脉旱季（五月至八月）的环流状况进行了系统分类。我们将分层 k 均值聚类方法应用于 1981 年至 2015 年期间 500 和 200 hPa 水平的日平均位势高度的 ERA 中期再分析数据。具体来说，通过结合位势异常的强度和位置的变化，我们确定了 12 种环流类型 (CT)。然后，我们通过分析日平均气温和降雨量的高分辨率网格数据集，建立了 CT 与秘鲁安第斯山脉 (PA) 地表条件之间的关系。我们的研究结果表明，强烈的降水和较低的最低气温通常与以副热带纬度（~30°S）和西经80°至70°之间为中心的上对流层槽（UTT）有关。此外，整个宾夕法尼亚州地区更加干燥和温暖的天气状况很大程度上与三个反气旋 CT 相关。每日最高（最低）气温的强烈负异常可能与日间（夜间）云量对辐射平衡的影响有关，也与UTT青睐的副热带冷空气平流有关。虽然在过去几十年的记录中，以较温暖（较冷）条件为特点的气候变化变得越来越频繁（越来越少），但气候变化发生的积极或消极趋势与气候变化的湿润和干燥特征之间没有系统性的联系。每年10个CT的频率与厄尔尼诺南方涛动显着相关，在前一个雨季，温暖和干燥（凉爽和湿润）的CT通常会在厄尔尼诺（拉尼娜）之前发生。
We present the first systematic classification of circulation regimes that characterize the Tropical Andes during the dry season (May–August). We apply the hierarchical k‐means clustering method to ERA‐Interim reanalysis data of daily mean geopotential height at 500‐ and 200‐hPa levels for the period 1981–2015. Specifically, by combining the variability in intensity and location of geopotential anomalies we identify 12 circulation types (CTs). We then establish the relationship between the CTs and surface conditions in the Peruvian Andes (PA) analysing high‐resolution gridded datasets of daily mean temperature and rainfall. Our results indicate that intense precipitations and low minimum temperatures are often associated with an Upper Tropospheric Trough (UTT) centred at subtropical latitudes (~30°S) and between 80° and 70°W of longitude. Moreover, drier and warmer conditions across the entire PA region are largely associated with three anticyclonic CTs. Strong negative anomalies in daily maximum (minimum) temperatures can be related to the effect of day (night) cloudiness in the radiative balance, but also to subtropical cold air advections favoured by the UTT. While CTs featuring warmer (colder) conditions have become more (less) frequent in the last decades of the record, there is no systematic link between positive or negative trends in occurrence and the wetter and drier character of the CTs. The annual frequencies of 10 CTs are significantly correlated with El Niño‐Southern Oscillation, with warmer and drier (cooler and wetter) CTs generally preceded by an El Niño (La Niña) in the previous wet season.