Compound Drought and Heatwaves at a Global Scale: The Role of Natural Climate Variability‐Associated Synoptic Patterns and Land‐Surface Energy Budget Anomalies
Compound Drought and Heatwaves at a Global Scale: The Role of Natural Climate Variability‐Associated Synoptic Patterns and Land‐Surface Energy Budget Anomalies
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DOI：
10.1029/2019jd031943
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发表时间：
2020-06
期刊：
影响因子：
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通讯作者：
S. Mukherjee;M. Ashfaq;A. Mishra
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文献类型：
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作者：
S. Mukherjee;M. Ashfaq;A. Mishra
复合干旱和热浪（CDHW）事件在最近的研究中获得了广泛的关注。然而，到目前为止，这些事件的识别过于简单，它们与自然气候变异的关系没有得到充分探讨。在这里，我们获得了每周自校准的帕尔默干旱严重程度指数（sc_PDSI）和每日最高温度的异常，以确定1982年至2016年地球仪26个气候区域的CDHW事件。利用Poisson广义线性模型（GLM）分析了季节性CDHW事件的年发生率及其与厄尔尼诺-南方涛动（ENSO）、太平洋年代际涛动（PDO）和北大西洋涛动（NAO）的冷暖位相的关系。ENSO与南半球夏季和秋季的CDHW事件有较强的相关性，而PDO在北半球夏季影响北方半球的北美西部地区的CDHW事件，这一点得到了大气环流异常和地表能量收支异常的综合支持。然而，NAO与CDHW事件的关联相对较弱。其他地区的CDHW发生是由这些大尺度自然强迫的组合驱动的。我们的分析还强调，在观测到的温度和降水的周至次月尺度异常的同现可能并不总是一致的观测和再分析。因此，在根据基于再分析的环流和地表能量收支解释这些观测到的异常时必须谨慎。总的来说，我们的分析提供了一个新的见解并发极端，并应有助于促进在这一领域的研究工作。
Compound drought and heatwave (CDHW) events have garnered much attention in recent studies. However, thus far, the identification of such events is oversimplified, and their association with natural climate variability is not fully explored. Here, we derive anomalies in the weekly self‐calibrated Palmer Drought Severity Index (sc_PDSI) and daily maximum temperatures to identify CDHW events from 1982 to 2016 over 26 climate regions across the globe. Using a Poisson Generalized Linear Model (GLM), we analyze yearly occurrences of seasonal CDHW events and their association with the warm and cold phases of El Nino Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and North Atlantic Oscillation (NAO). ENSO exhibits robust association with CDHW events over the Southern Hemisphere during the austral summer and fall, while PDO influences their occurrences over the Western North America in the Northern Hemisphere during the boreal summer, which is supported by the composites of anomalies in the atmospheric circulations and surface energy budget. However, NAO association with CDHW events is relatively weak. The CDHW occurrence over other regions is driven by a combination of these large‐scale natural forcing. Our analyses also highlight that the cooccurrence of weekly to submonthly scale anomalies in the observed temperature and precipitation may not be always aligned between the observations and the reanalysis. Therefore, caution must be exercised while explaining such observed anomalies on the basis of reanalysis‐based circulations and surface energy budget. Overall, our analyses provide a new insight towards concurrent extremes and should help foster research efforts in this area.