Droughts and heatwaves are natural phenomena that can cause severe damage to the economy, infrastructure, human health, and agriculture, among others. However, in recent years, it has been noted that their combined effect, known as compound drought and heatwave events (CDHE), often results in even greater harm. The main aim of this study was to identify CDHEs in this region during summers from 1950 to 2022 and assess the frequency and intensity of these events. To this end, the periods of droughts and heatwaves that occurred between 1950 and 2022 were determined, and the recurrence, extent, and intensity of these phenomena were evaluated. In this study, 1-month Standard Precipitation Index (SPI) values calculated for each summer day were used to identify droughts, while heatwaves were defined as a period of five or more consecutive days when the daily maximum air temperature (T) was higher than the 90 percentile of T. Precipitation and T data (with a spatial resolution 0.25° x 0.25°) were obtained from the European Centre of Medium-Range Weather Forecast ERA-5 reanalysis dataset. The study showed that in most of the eastern part of the Baltic Sea region, the number of drought days had decreased from 1950 to 2022, while the number of heatwave days had increased significantly. In total, ten CDHEs were identified during the summers of 1950–2022. Eight of these events were recorded in 1994 or later. However, a statistically significant increase of CDHEs was found only in a small part of the study area.

中文翻译：

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波罗的海东部地区复合干旱热浪事件

干旱和热浪是自然现象，可能对经济、基础设施、人类健康和农业等造成严重损害。然而，近年来，人们注意到它们的综合效应，即所谓的复合干旱和热浪事件（CDHE），往往会造成更大的危害。本研究的主要目的是确定 1950 年至 2022 年夏季该地区的 CDHE，并评估这些事件的频率和强度。为此，确定了 1950 年至 2022 年间发生的干旱和热浪的时期，并评估了这些现象的重现、范围和强度。在这项研究中，每个夏季每天计算的 1 个月标准降水指数 (SPI) 值用于识别干旱，而热浪被定义为连续 5 天或以上每日最高气温 (T) 高于90% 的 T 值。降水和 T 数据（空间分辨率为 0.25° x 0.25°）取自欧洲中期天气预报中心 ERA-5 再分析数据集。研究显示，在波罗的海地区东部大部分地区，1950年至2022年期间，干旱日数有所减少，而热浪日数则大幅增加。 1950 年至 2022 年夏季期间，总共发现了 10 个 CDHE。其中 8 起事件是在 1994 年或之后记录的。然而，仅在研究区域的一小部分区域发现了 CDHE 的统计显着增加。