Hotspots for warm and dry summers in Romania

The combined effect of hot and dry extremes can have disastrous consequences for society, the economy, and the environment. While a significant number of studies have been conducted regarding the variability of the individual hot or dry extremes in Romania, the evaluation of the combined effect of these extremes (e.g., compound effect) is still lacking for this region. Thus, in this study, we have assessed the spatiotemporal variability and trends of hot and dry summers in Romania, between 1950 and 2020, and we have analyzed the relationship between the frequency of hot summers and the prevailing large-scale atmospheric circulation. The length, spatial extent, and frequency of heat waves (HWs) in Romania present decadal variations, with the rate of increase being accelerated after the 1990s. The smallest number of HWs was observed between 1970 and 1985, while the highest number of HWs has been recorded over the last 2 decades (i.e., 2001-2020). The hottest years, in terms of heat wave duration and frequency, were 2007, 2012, 2015, and 2019. One of the key drivers of hot summers, over our analyzed region, is the prevailing large-scale circulation, featuring an anticyclonic circulation over the central and eastern parts of Europe and enhanced atmospheric blocking activity associated with positive temperature anomalies underneath. The results from this study can help improve our understanding of the spatiotemporal variability of hot and dry summers over Romania, as well as their driving mechanisms, which might lead to a better predictability of these extreme events in the region.

Automated summary

This study assesses the spatiotemporal variability of hot and dry summers in Romania between 1950 and 2020, and analyzes the relationship with the prevailing large-scale atmospheric circulation. The length, spatial extent, and frequency of heat waves show decadal variations, with an accelerated increase after the 1990s. The prevailing large-scale circulation and enhanced atmospheric blocking activity are key drivers of hot summers in Romania.