Impacts upon vulnerable areas such as mountain ranges may become greater under a future scenario of adverse climatic conditions. In this sense, the concurrence of long dry spells and extremely hot temperatures can induce environmental risks such as wildfires, crop yield losses or other problems, the consequences of which could be much more serious than if these events were to occur separately in time (e.g. only long dry spells). The present study attempts to address recent and future changes in the following dimensions: duration (D), magnitude (M) and extreme magnitude (EM) of compound dry–hot events in the Pyrenees. The analysis focuses upon changes in the extremely long dry spells and extremely high temperatures that occur within these dry periods in order to estimate whether the internal structure of the compound event underwent a change in the observed period (1981–2015) and whether it will change in the future (2006–2100) under intermediate (RCP4.5, where RCP is representative concentration pathway) and high (RCP8.5) emission scenarios. To this end, we quantified the changes in the temporal trends of such events, as well as changes in the bivariate probability density functions for the main Pyrenean regions. The results showed that to date the risk of the compound event has increased by only one dimension – magnitude (including extreme magnitude) – during the last few decades. In relation to the future, increase in risk was found to be associated with an increase in both the magnitude and the duration (extremely long dry spells) of the compound event throughout the Pyrenees during the spring under RCP8.5 and in the northernmost part of this mountain range during summer under this same scenario.

中文翻译：

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评估未来干热复合事件结构的内部变化：以比利牛斯山脉为例

在未来气候条件不利的情况下，对山脉等脆弱地区的影响可能会更大。从这个意义上说，长期干旱和极端高温的同时发生会导致环境风险，例如野火、作物产量损失或其他问题，其后果可能比这些事件在时间上分别发生（例如只有长时间的干旱）。本研究试图在以下维度解决近期和未来的变化：持续时间 ( D )、幅度 ( M) 和比利牛斯山脉复合干热事件的极端震级 (EM)。分析集中在这些干旱期发生的极长干旱期和极高温度的变化，以估计复合事件的内部结构是否在观察期（1981-2015）发生了变化，是否会发生变化。未来（2006-2100 年）在中等（RCP4.5，其中 RCP 是代表性浓度路径）和高（RCP8.5）排放情景下。为此，我们量化了此类事件的时间趋势变化，以及主要比利牛斯山脉地区的双变量概率密度函数的变化。结果表明，迄今为止，复合事件的风险在过去几十年中仅增加了一个维度——震级（包括极端震级）。