赣江流域骤发干旱精准识别及其演变规律与驱动机制研究

As a newly recognized phenomenon of natural disasters, flash droughts have the characteristics of suddenness and tremendous influence on society and economy. In recent years, due to the intensification of climate warming, flash droughts have occurred more frequently in many parts of the world, and have caused serious impacts on agricultural production and social economy. However, it is unclear how to accurately identify flash droughts and their evolution and driving mechanisms. The Gan River Basin is an important area of ecological agriculture in the humid basins of southern China, and is threatened by flash droughts. Based on the VIC model, the rate of intensification (the degree of rapidity) and short time scale method, this study defines the quantitative monitoring indicators of flash droughts. It will improve the identification accuracy of flash droughts. The spatial and temporal characteristics of flash droughts with different intensity levels are investigated based on the flash drought magnitude index (FDMI), flash drought severity and coverage index (FDSCI). From the land surface process and atmospheric circulations, this study explores the driving mechanisms of flash drought events at different intensity levels. With this project, it will provide a scientific basis for improving the detection and prediction of flash drought, mitigating their associated potential losses, and ensuring food security.

骤发干旱作为一种新认识到的自然灾害现象，具有突发性、影响与危害的严重性等特征。近年来由于气候变暖加剧，世界上许多地区骤发干旱事件发生越来越频繁，对农业生产和社会经济造成严重影响。但关于骤发干旱事件如何精准识别及其演变规律和驱动机制等问题尚不清楚。赣江流域是我国南方湿润流域生态农业重要区域，深受骤发干旱事件威胁。本项目拟通过VIC陆面水文模型及强度变化率（迅速程度指标）和短时间尺度方法，科学定义骤发干旱定量监测指标，提高赣江流域骤发干旱事件的识别准确度；利用单站点骤发干旱量级指数和单位时间骤发干旱严重性与覆盖范围指数，揭示不同强度等级赣江流域骤发干旱事件的时空特征与演变规律；从地表过程和大气环流形势两方面，探明不同强度等级赣江流域骤发干旱事件演变特征的驱动机制。旨在为赣江流域提高骤发干旱事件的监测能力、规避骤发干旱风险、保障粮食安全等提供科学参考依据。

骤发干旱是一种在短期内迅速发生发展，并伴随着高温和土壤含水量短缺为主要特征的干旱事件，这对自然环境和社会经济造成重大影响。目前，对于不同强度等级的骤发干旱演变规律研究较为鲜见，在模式中的模拟能力有待进一步探究。本项目以赣江流域为例，基于骤发干旱严重程度指数探究了不同强度等级骤发干旱事件的时空变化特征。结果表明：总云量、降水和相对湿度的减少，以及500 hPa位势高度、对流抑制能、气温、水汽压饱和差和风速的增加，为骤发干旱的发生提供了有利条件。尽管流域中部和南部的骤发干旱发生频次较高，但流域北部的严重程度相对较高。极端和超级极端骤发干旱事件呈显著下降趋势，而中度和重度骤发干旱事件呈轻微上升趋势。随着骤发干旱等级的增加，骤发干旱持续时间和单位强度（非线性项）之间的交互作用增加，进而加大骤发干旱的严重程度。7–10月期间骤发干旱发生的频次较多、持续时间较长。赣江流域南部发生中度和重度骤发干旱事件的概率相对较高，而流域北部容易发生极端和超级极端骤发干旱事件。赣江流域中度、重度、极端和超级极端骤发干旱事件的重现期约为3–6、5–15、10–50和30–200年。此外，本项目从水量平衡角度，基于观测数据和模式模拟资料评估了我国骤发干旱时空变化特征及其与复合极端气象事件的联系。结果表明：我国骤发干旱事件总体上呈增加趋势，尤其是在SSP585情景下。复合高温、大气干燥和大风事件为骤发干旱事件的发生和维持提供了有利条件。未来复合极端气象事件和骤发干旱事件的相互作用将加强。本项目成果为丰富骤发干旱定义，提高骤发干旱监测和预测能力，深入理解骤发干旱基本特征以及为减轻骤发干旱造成的损失提供了科学参考依据。