Drought and heat events, such as the 2018 European drought, interact with the exchange of energy between the land surface and the atmosphere, potentially affecting albedo, sensible and latent heat fluxes, as well as CO₂ exchange. Each of these quantities may aggravate or mitigate the drought, heat, their side effects on productivity, water scarcity and global warming. We used measurements of 56 eddy covariance sites across Europe to examine the response of fluxes to extreme drought prevailing most of the year 2018 and how the response differed across various ecosystem types (forests, grasslands, croplands and peatlands). Each component of the surface radiation and energy balance observed in 2018 was compared to available data per site during a reference period 2004–2017. Based on anomalies in precipitation and reference evapotranspiration, we classified 46 sites as drought affected. These received on average 9% more solar radiation and released 32% more sensible heat to the atmosphere compared to the mean of the reference period. In general, drought decreased net CO₂ uptake by 17.8%, but did not significantly change net evapotranspiration. The response of these fluxes differed characteristically between ecosystems; in particular, the general increase in the evaporative index was strongest in peatlands and weakest in croplands.

This article is part of the theme issue ‘Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale’.

干旱和高温事件，例如 2018 年欧洲干旱，与地表和大气之间的能量交换相互作用，可能影响反照率、感热和潜热通量以及 CO ₂交换。这些数量中的每一个都可能加剧或减轻干旱、高温及其对生产力、水资源短缺和全球变暖的副作用。我们使用了欧洲 56 个涡旋协方差点的测量值来检查通量对 2018 年大部分时间盛行的极端干旱的响应，以及不同生态系统类型（森林、草原、农田和泥炭地）的响应有何不同。将 2018 年观测到的地表辐射和能量平衡的每个组成部分与 2004-2017 年参考期间每个站点的可用数据进行了比较。根据降水和参考蒸发量的异常，我们将 46 个地点归类为受干旱影响的地点。与参考时期的平均值相比，这些地区平均多接收了 9% 的太阳辐射，并向大气释放了 32% 的显热。一般来说，₂吸收增加了 17.8%，但没有显着改变净蒸发量。这些通量的响应因生态系统而异；尤其是，泥炭地蒸发指数的总体增长最强，农田最弱。

本文是主题问题“2018 年欧洲严重干旱和热浪的影响：从场地到大陆尺度”的一部分。