在全球气候变暖和快速城市化的背景下，极端高温事件频发已成为威胁人类健康和社会可持续发展的重要问题，尤其是在人口稠密、经济发达的长江三角洲（简称“长三角”）地区。本研究基于1961-2020年长三角地区气象观测数据，系统分析了日最高气温、日平均气温及高温热浪指数的变化趋势。同时，结合WRF（Weather Research and Forecasting）模式开展敏感性试验，评估城市下垫面对极端高温的影响。结果表明：（1）长三角地区的日最高气温和日平均气温在过去几十年间均呈显著上升趋势，其中日最高气温的增幅［0. 194 ℃·（10a）-1］高于日平均气温［0. 187 ℃·（10a）-1］。通过 Pettitt检验，研究发现两类气温序列在1993年发生显著突变，突变前气温呈下降趋势，而突变后则转为上升趋势。（2）高温热浪发生频次、持续时间和强度分别以 0. 190 time·（10a）-1、0. 475 d·（10a）-1和 0. 772 ℃·time-1·（10a）-1的速率显著上升。通过分析热浪指数的突变情况，发现热浪指数的突变点出现在 2000年，滞后于气温的突变点。突变前，热浪指数呈现下降趋势，而突变后则转为上升趋势，且热浪强度的增幅远超频次和持续时间。（3）进一步分析表明，城市化对气温和高温热浪的影响显著。城市站点的日最高气温［0. 243 ℃·（10a）-1］和日平均气温［0. 261 ℃·（10a）-1］上升速率均显著高于农村站点［0. 171 ℃·（10a）-1、0. 167 ℃·（10a）-1］，表明城市化对增温具有放大作用。同时，城市站点的高温热浪指数上升趋势明显强于农村站点，表明城市化可能增强了高温热浪的发生。（4）数值模拟表明，WRF模式能够较好地再现模拟区域的气温变化特征。城市下垫面的存在显著影响了城市站点的气温，尤其在高温日时期，在夜间表现更明显。城市下垫面通过改变地表能量收支（如感热通量、潜热通量和地表储热），增强了城市站点在高温日时期的地表能量变化，加剧了在高温日时期的气温，而农村站点受城市化影响较小，表明城市化过程对城市区域的高温影响更加明显。综上所述，长三角地区的极端高温事件频次、强度和持续时间在过去几十年间呈现显著上升趋势，且城市化在其中发挥了重要的放大作用。随着城市化的进一步发展，极端高温事件的频率和强度可能持续增加，因此，制定有效的适应策略和缓解措施至关重要。

Under the background of global climate warming and rapid urbanization，extreme heat events have be‐ come a significant threat to human health and social sustainable development，particularly in Yangtze River Delta （YRD），a densely populated and economically developed region. Based on meteorological observations from 1961 to 2020，this study systematically analyzes the trends of daily maximum temperature，daily mean tempera‐ ture，and heat wave indices in the YRD. Additionally，sensitivity experiments using the WRF model are conduct‐ ed to assess the impact of urban land use on extreme high temperature events. The results show that：（1）Both daily maximum temperature and daily mean temperature in the YRD have exhibited significant upward trends over the past few decades，with the increase in daily maximum temperature［0. 194 ℃·（10a）-1］being more pro‐ nounced than that in daily mean temperature［0. 187 ℃·（10a）-1］. Pettitt test results indicate a significant change point in 1993，with temperatures showing a downward trend before the change point and shifting to an upward trend after the change point.（2）The frequency，duration，and intensity of heat waves have significantly in‐ creased at rates of 0. 190 time·（10a）-1，0. 475 d·（10a）-1，and 0. 772 ℃·time-1·（10a）-1，respectively，indicating that the frequency，duration and intensity of heat waves increased significantly. The change point for heat wave indices lags behind that of temperature change point and occurring in 2000. It showed an insignificant downward trend before the change point，and turning into a significant upward trend after the change. Intensity of heat wave increasing at a much higher rate than frequency and duration.（3）Urbanization has a significant impact on tem‐ perature and heat waves. The daily maximum temperature［0. 243 ℃·（10a）-1］and daily mean temperature ［0. 261 ℃·（10a）-1］of urban stations being significantly higher than those of rural stations［0. 171 ℃·（10a）-1、 0. 167 ℃·（10a）-1］，suggesting that urbanization has an amplifying effect on warming. The increasing trends of heat wave indices at urban stations are also significantly stronger than those at rural stations，indicating that ur‐ banization may enhance the occurrence of heat waves.（4）The WRF model can effectively simulate the hourly variation of temperature，and urban land use significantly affect urban station temperatures，especially during hot days，with a more pronounced effect at night. Urban underlying surfaces enhance the surface energy changes of urban stations during hot days by changing the surface energy budget（such as sensible heat flux，latent heat flux and surface heat storage），which intensifies the temperature during hot days，while rural stations are less affect‐ ed by urbanization. This indicates that the urbanization process has a more obvious impact on extreme high tem‐ perature events in urban areas. The frequency，intensity and duration of heat waves in the Yangtze River Delta re‐ gion have shown a significant upward trend in the past few decades，and urbanization has played an important amplifying role in this. With the further development of urbanization，the frequency and intensity of extreme high temperature events are likely to increase further，highlighting the necessity of developing effective adapta‐ tion strategies and mitigation measures.