Drought conditions are experiencing substantial changes due to global warming, but the contributions of changes in temperature, precipitation, and associated extremes to drought severity at the regional scale remain an important topic for climate change research. Northern East Asia (NEA) has experienced frequent climate extremes and is very sensitive and vulnerable to climate change. We analyze the spatiotemporal variations of the Standardized Precipitation-Evapotranspiration Index (SPEI) and 7 ETCCDI extreme climate indices (ECIs), the relationship between SPEI and ECIs, and the mechanism for SPEI changes during 1979–2018. Observations indicate a significant increasing trend in drought severity in NEA. Warm-related ECIs show a similar increasing trend, while precipitation-related ECIs (heavy precipitation days and extreme precipitation intensity) display no significant trend. Correlation analysis indicates that the intensification of drought in NEA is strongly related to the changes in average temperature and related ECIs, while the correlation with precipitation and related ECIs is weak and insignificant. A coupled model (CSIRO-MK3.6.0) simulation driven by realistic external forcing reasonably reproduced the observed NEA SPEI changes and the relationships with temperature, precipitation, and the related-ECIs. Attribution analysis is further conducted using the model simulations. The increased severity of NEA drought is attributed to remarkable increases in potential evapotranspiration (PET), caused by increases in surface net radiation and the vapor pressure deficit (VPD), and the VPD makes a more significant contribution to the decrease in SPEI. Increased PET intensifies the drought condition in NEA even though the moisture supply (precipitation) experiences no decrease trends during 1979–2018. The strong warming and increase in warm-related ECIs drive increases in the VPD, intensifying the evaporative demand and amplifying the drought conditions in NEA. Our findings highlight the connections between drought risks and intense warm extremes at regional scales and the potential role of external radiative forcing in causing these changes.

由于全球变暖，干旱条件正在经历重大变化，但温度、降水和相关极端事件对区域尺度干旱严重程度的影响仍然是气候变化研究的重要课题。东北亚 (NEA) 经历了频繁的极端气候事件，对气候变化非常敏感和脆弱。我们分析了 1979-2018 年标准化降水-蒸发蒸腾指数 (SPEI) 和 7 个 ETCCDI 极端气候指数 (ECI) 的时空变化、SPEI 和 ECI 之间的关系以及 SPEI 变化的机制。观测表明，NEA 的干旱严重程度有显着增加的趋势。与暖相关的 ECI 显示出类似的增加趋势，而与降水相关的ECI（强降水日数和极端降水强度）没有显示出明显的趋势。相关性分析表明，东北亚地区干旱加剧与平均气温及相关ECI变化密切相关，而与降水及相关ECI的相关性较弱且不显着。由真实外强迫驱动的耦合模型（CSIRO-MK3.6.0）模拟合理地再现了观测到的 NEA SPEI 变化以及与温度、降水和相关 ECI 的关系。使用模型模拟进一步进行归因分析。NEA 干旱的严重程度增加归因于潜在蒸散量 (PET) 的显着增加，这是由于地表净辐射和蒸气压亏缺 (VPD) 增加引起的，VPD对SPEI下降的贡献更为显着。尽管水分供应（降水）在 1979-2018 年期间没有减少趋势，但增加的 PET 加剧了 NEA 的干旱状况。强烈的变暖和与温暖相关的 ECI 的增加驱动了 VPD 的增加，加剧了蒸发需求并加剧了 NEA 的干旱条件。我们的研究结果强调了区域尺度上干旱风险与强烈温暖极端事件之间的联系，以及外部辐射强迫在导致这些变化中的潜在作用。强烈的变暖和与温暖相关的 ECI 的增加驱动了 VPD 的增加，加剧了蒸发需求并加剧了 NEA 的干旱条件。我们的研究结果强调了区域尺度上干旱风险与强烈温暖极端事件之间的联系，以及外部辐射强迫在导致这些变化中的潜在作用。强烈的变暖和与温暖相关的 ECI 的增加驱动了 VPD 的增加，加剧了蒸发需求并加剧了 NEA 的干旱条件。我们的研究结果强调了区域尺度上干旱风险与强烈温暖极端事件之间的联系，以及外部辐射强迫在导致这些变化中的潜在作用。