复合高温干旱事件会导致作物减产，对粮食安全构成威胁。由于两个极端事件的复合效应，影响会高于单一的极端事件。在全球变暖的背景下，复合高温干旱事件的频率增加带来了艰巨而紧迫的挑战，对包括水资源、生态系统功能和公共卫生在内的各个部门的影响越来越大。在全球升温背景下，中国干旱和极端高温的频率和强度都有所增加，预计未来还可能进一步增加，对中国的多个部门造成破坏性影响，给包括农业在内的多个部门带来巨大风险。因此，了解中国复合高温干旱事件的农业风险，对于应对全球变暖下的极端天气气候事件并制定适应性措施是非常重要的。本文的主要研究内容及结果如下：
（1）以作物产量为参考数据，通过计算标准化降水指数（SPI）、标准化降水蒸散指数（SPEI）、自校准Palmer干旱指数（scPDSI）构建不同类型的标准化复合高温干旱指数（SCEI（SPI）、SCEI（SPEI）、SCEI（scPDSI）），评估了中国1980-2018年基于作物产量的多个指标的监测表现。研究发现SCEI与广泛使用的单一SPI、SPEI和scPDSI指标均具有较强的相关性，证明了SCEI指标在中国区域进行复合高温干旱事件监测的适用性。在中国大部分区域作物产量与这些指标之间均存在显著的相关性，且干旱/半干旱区的相关性高于湿润地区。不同指标在不同地区的相关性有差异，基于产量的监测效果表明SCEI表现相对优于SPI、SPEI和scPDSI等干旱指标，因此SCEI在中国干旱以及复合高温干旱监测、预警以及评估等方面具有重要应用价值。
（2）基于CN05.1历史观测数据以及中国区域CMIP6降尺度未来预估数据，结合3个干旱指标（SPI、SPEI和scPDSI）与日最高温度提取复合高温干旱事件的不同特征（频率、持续时间、强度和开始时间），分析中国历史时期（1961-2014）和未来时期（2015-2100）多特征复合高温干旱事件分布与变化。结果表明在历史时期，中国复合高温干旱事件的频率、持续时间和强度主要增加的区域在东北到西南一带，降低的区域主要在中部以及西北部分地区。复合高温干旱事件在未来近期（2021-2040年）、中期（2041-2060年）和远期（2081-2100年）的频率、持续时间和强度上均显著增加，其中东南和西北地区的增加幅度尤为显著，同时发生时间提前，表明未来复合高温干旱事件将更频繁、持续时间更长、强度更大、发生时间更早。
（3）探究未来农业风险分布以及其随时间的动态变化。根据复合高温干旱事件的自然灾害特征构建了综合危险性指标，同时考虑暴露度指标和脆弱性指标等社会经济因素，评估了未来复合高温干旱事件农业风险的动态变化。结果表明，在未来近中远三个时期，农业风险较高的区域主要有中国中部、东部，西南地区以及东北地区。随着复合高温干旱事件危险性增加和脆弱性的异质性变化，从2030年到2100年，全国大部分区域的复合高温干旱事件的农业风险将持续增加，不同指标的动态风险具有差异，例如，基于SPI指标的复合高温干旱事件的未来农业动态风险在2080年达到峰值，基于SPEI和scPDSI指标的未来农业动态风险一直增加直到2100年。这些结果反映了通过考虑不同特征和不同指标对于理解和管理复合高温干旱事件的复杂农业风险是必要的。本研究为气候变化背景下中国未来复合高温干旱事件的农业风险评估提供了有价值的信息。

Compound hot-dry events lead to crop yield reduction and pose a threat to food security. The combined effects of these two extreme events result in greater impacts than a single extreme event alone. Against the backdrop of global warming, the increasing frequency of compound hot-dry events presents significant and urgent challenges, affecting various sectors including water resources, ecosystem functions, and public health. In China, the frequency and intensity of droughts and extreme heat have increased under global warming and are expected to further intensify in the future, causing destructive impacts across multiple sectors, including agriculture, and posing significant risks. Therefore, understanding the agricultural risks associated with compound hot-dry events in China is crucial for addressing extreme weather and climate events under global warming and for developing adaptive measures. The main research contents and findings of this paper are as follows：
(1) Using crop yield as reference data, this study evaluated the performance of multiple indices based on crop yield from 1980 to 2018 in China, including the Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), self-calibrated Palmer Drought Severity Index (scPDSI), and the construction of different types of Standardized Compound Event Indices (SCEI(SPI), SCEI(SPEI), SCEI(scPDSI)). The research found that SCEI is strongly correlated with widely used SPI, SPEI, and scPDSI indices, demonstrating the applicability of SCEI indices for monitoring compound hot-dry events in China. Significant correlations were found between crop yield and these indices in most regions of China, with higher correlations observed in arid/semi-arid regions compared to humid areas. There were differences in the correlations of different indices in different regions. The monitoring effectiveness of SCEI based on yield was relatively better than SPI, SPEI, and scPDSI drought indices, indicating the significant practical value of SCEI in monitoring, warning, and assessing droughts and compound hot-dry events in China.
(2) Utilizing historical observational data from CN05.1 and regional CMIP6 downscaled future projection data for China, this study constructed different characteristics of compound hot-dry events (frequency, duration, magnitude, and timing) based on three drought indices (SPI, SPEI, and scPDSI) and relative thresholds of daily maximum temperature. The distribution and changes of multi-characteristic compound hot-dry events during the historical span (1961-2014) and future span (2015-2100) were analyzed. The results indicate that during the historical period, the regions experiencing increases in frequency, duration, and magnitude of compound hot-dry events were predominantly situated from the northeast to the southwest, while decreases were observed in central and northwest regions. In the short term (2021-2040), mid-term (2041-2060), and long term (2081-2100) future periods, significant increases in the frequency, duration, and magnitude of compound hot-dry events were observed, with larger increases in the southeast and northwest regions. Additionally, the timing of these events was advanced, indicating that future compound hot-dry events will be more frequent, longer-lasting, more severe, and occur earlier. This underscores the need to monitor the changes in different characteristics of compound events in the future to mitigate the adverse impacts of climate change.
(3) This paper explores the distribution of agricultural (and demographic) risks associated with future compound hot-dry events and their dynamic changes over time. Based on the characteristics of compound heatwave-drought events as natural disasters, a comprehensive risk index was constructed, taking into account socioeconomic factors such as exposure and vulnerability, to assess the dynamic changes in the agricultural risk of compound hot-dry events. The results indicate that in the short term, mid-term, and long term future periods, regions with higher agricultural risks are mainly located in central and eastern China, southwestern regions, and northeastern China. As the hazard of compound hot-dry events increases and vulnerability exhibits heterogeneous changes, from 2030 to 2100, agricultural risks associated with compound hot-dry events continue to increase in most regions nationwide. The dynamic risks based on different indices exhibit variations; for example, agricultural dynamic risks based on SCEI (SPI) peak in 2080, while those based on SCEI (SPEI) and SCEI (scPDSI) continue to increase until 2100. This reflects the necessity of considering different characteristics and indices (from a multivariate perspective) for understanding and managing the complex risks of compound hot-dry events. This study provides valuable information for assessing agricultural risks associated with future compound hot-drought events in China under the backdrop of global warming and formulating adaptation measures.