The 2018 drought was one of the worst European droughts of the twenty-first century in terms of its severity, extent and duration. The effects of the drought could be seen in a reduction in harvest yields in parts of Europe, as well as an unprecedented browning of vegetation in summer. Here, we quantify the effect of the drought on net ecosystem exchange (NEE) using five independent regional atmospheric inversion frameworks. Using a network of atmospheric CO₂ mole fraction observations, we estimate NEE with at least monthly and 0.5° × 0.5° resolution for 2009–2018. We find that the annual NEE in 2018 was likely more positive (less CO₂ uptake) in the temperate region of Europe by 0.09 ± 0.06 Pg C yr⁻¹ (mean ± s.d.) compared to the mean of the last 10 years of −0.08 ± 0.17 Pg C yr⁻¹, making the region close to carbon neutral in 2018. Similarly, we find a positive annual NEE anomaly for the northern region of Europe of 0.02 ± 0.02 Pg C yr⁻¹ compared the 10-year mean of −0.04 ± 0.05 Pg C yr⁻¹. In both regions, this was largely owing to a reduction in the summer CO₂ uptake. The positive NEE anomalies coincided spatially and temporally with negative anomalies in soil water. These anomalies were exceptional for the 10-year period of our study.

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

从严重程度，程度和持续时间来看，2018年的干旱是二十一世纪欧洲最严重的干旱之一。干旱的影响可见于欧洲部分地区收成减产，以及夏季前所未有的植被褐变。在这里，我们使用五个独立的区域大气反转框架来量化干旱对净生态系统交换（NEE）的影响。使用大气CO ₂摩尔分数观测网络，我们估计2009-2018年的NEE至少具有每月一次和0.5°×0.5°的分辨率。我们发现，在欧洲温带地区，2018年的年度NEE可能更积极（减少CO ₂吸收）0.09±0.06 Pg C yr ^-1（平均值±sd）与最近十年的平均值-0.08±0.17 Pg C yr ^-1相比，使该地区在2018年接近碳中和。类似地，我们发现欧洲北部地区的年度NEE异常为正0.02±0.02 Pg C yr ^-1的十年平均值为-0.04±0.05 Pg C yr ^-1的十年平均值。在这两个地区，这主要是由于夏季CO ₂吸收量减少。NEE的正异常在空间和时间上与土壤水中的负异常重合。这些异常在我们的研究的10年期间是异常的。

本文是主题问题``欧洲2018年严重干旱和热浪的影响：从站点到大陆范围的影响''的一部分。