Large infrequent rain events dominate the hydroclimate of Rapa Nui (Easter Island)
Large infrequent rain events dominate the hydroclimate of Rapa Nui (Easter Island)
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DOI：
10.1007/s00382-022-06143-1
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发表时间：
2022-01
期刊：
影响因子：
4.6
通讯作者：
N. Steiger;W. D'Andrea;J. Smerdon;R. Bradley
中科院分区：
文献类型：
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作者：
N. Steiger;W. D'Andrea;J. Smerdon;R. Bradley
拉帕努伊岛（复活节岛）上波利尼西亚文明的历史在共同时代已经证明了人类与环境之间脆弱的关系。社会动态，森林砍伐，土地退化和气候变化都被认为是拉帕努伊定居历史和社会变革的重要组成部分。此外，东南太平洋的气候动态具有重大的全球影响。虽然拉帕努伊的湿地包含了重要的沉积学档案，可用于重建岛上过去的水文变化，但人们对岛上水文气候与区域气候学基本方面之间的联系知之甚少。在这里，我们提出了一个水文气候学的拉帕努伊岛显示，有一个明确的季节性周期的降水，与潮湿的几个月收到几乎两倍的降水量为干燥的几个月。这种季节性循环可以用南太平洋副热带高压位置和强度的季节性变化来解释。对于年际降水变化，我们发现，发生罕见的，大的降雨事件解释了92%的观测到的年平均降水量时间序列的方差。这些事件中约有三分之一（33%）与大气河流有关，21%与典型冷锋天气系统有关，其余的则以截止低压和其他天气尺度风暴系统为特征。这些大暴雨事件作为一个整体，受南太平洋副热带高压的纵向位置控制最强。这个反气旋的纵向位置解释了大雨事件频率的21%的变化，而其余的变化则无法由任何其他主要的大气-海洋动力学来解释。我们发现，在观测时代，似乎没有大的降雨事件的数量和任何其他主要的气候现象之间的线性关系。随着全球变暖，南太平洋副热带高压预计将加强和向西扩展，我们的结果意味着拉帕努伊将在未来的干旱年数增加。
The history of the Polynesian civilization on Rapa Nui (Easter Island) over the Common Era has come to exemplify the fragile relationship humans have with their environment. Social dynamics, deforestation, land degradation, and climatic shifts have all been proposed as important parts of the settlement history and societal transformations on Rapa Nui. Furthermore, climate dynamics of the Southeast Pacific have major global implications. While the wetlands of Rapa Nui contain critical sedimentological archives for reconstructing past hydrological change on the island, connections between the island’s hydroclimate and fundamental aspects of regional climatology are poorly understood. Here we present a hydroclimatology of Rapa Nui showing that there is a clear seasonal cycle of precipitation, with wet months receiving almost twice as much precipitation as dry months. This seasonal cycle can be explained by the seasonal shifts in the location and strength of the climatological south Pacific subtropical anticyclone. For interannual precipitation variability, we find that the occurrence of infrequent, large rain events explains 92% of the variance of the observed annual mean precipitation time series. Approximately one third (33%) of these events are associated with atmospheric rivers, 21% are associated with classic cold-front synoptic systems, and the remainder are characterized by cut-off lows and other synoptic-scale storm systems. As a group, these large rain events are most strongly controlled by the longitudinal position of the south Pacific subtropical anticyclone. The longitudinal location of this anticyclone explains 21% of the variance in the frequency of large rain events, while the remaining variance is left unexplained by any other major atmosphere-ocean dynamics. We find that over the observational era there appears to be no linear relationship between the number of large rain events and any other major climate phenomena. With the south Pacific subtropical anticyclone projected to strengthen and expand westward under global warming, our results imply that Rapa Nui will experience an increase in the number of dry years in the future.