气候变暖背景下土壤湿度异常对我国干旱半干旱地区高温热浪影响的定量化研究

Heat wave is one of the most severe extreme meteorological disasters. The global warming and soil moisture decrease have significant effects on the increase of heat waves. The arid and semi-arid areas in China experience the most prominent warming and drying. However, the characteristics of heat waves change and response to soil moisture anomaly, especially for the quantitative impact in the areas, haven’t been paid too much attention. This program will investigate the characteristics of heat waves change in the arid and semi-arid areas over China under global warming, and compare with other climatic regions based on multiple definitions of heat waves. By the dynamical adjustment methodology, we divide the heat waves into dynamically induced change and local feedback forced change, and investigate the mechanism of heat waves change from the two aspects. On this basis we will build the statistical model between soil moisture and heat waves so as to reveal the quantitative impact of previous soil moisture anomaly on the later heat waves combining with the numerical simulation. This program will further the understanding of extreme climate changes in arid and semi-arid regions and provide theoretical basis for the improvement of climate risk assessment and predicting future heat waves in China.

高温热浪是全球最为严重的极端气象灾害之一，气候变暖和土壤湿度减小是造成高温热浪增强增多的重要原因。然而，作为暖干化最明显的区域，我国干旱半干旱区高温热浪的变化特征及其对土壤湿度异常的响应机制，特别是定量化影响还缺乏研究。本项目立足于我国干旱半干旱地区，以土壤湿度气温反馈作用为切入点，主要开展以下研究：基于多种热浪指数，研究在全球变暖背景下该地区高温热浪的变化特征以及与其他地区的差异性；利用动力调整方法，将高温热浪变化分解为大尺度动力影响和局地反馈作用，从两个方面探讨高温热浪的影响机制；在此基础上，构建土壤湿度高温热浪的统计模型，结合数值模式，揭示前期土壤湿度异常对后期高温热浪的定量贡献。本项目的实施不仅能加深对干旱半干旱地区极端气候变化的理解，同时也能够为提高我国气候风险评估和极端高温的预测能力提供理论依据。

高温热浪是全球最为严重的极端气象灾害之一，研究高温热浪变化的区域差异性及其影响机制对提高我国气候风险评估和极端高温的预测能力具有重要意义。本项目基于多种干湿变化和热浪指数，研究了在全球变暖背景下不同气候区干湿变化和高温热浪的时空分布和变化特征，并分析了年代际振荡调制和海陆热力差异等大尺度系统对北半球夏季高温热浪的影响。通过研究，发现了干湿指数的准20年周期特征及其影响机制，并从气候区角度分析了高温热浪变化的敏感区，突出了干旱半干旱区的特殊性，揭示了海气相互作用对热浪影响的关键区。在此基础上，基于CMIP5多模式的历史试验结果，通过与再分析数据对比分析，评估了其对不同气候区气温的模拟能力，并利用相似动力误差订正方法对历史和未来情景的模拟结果进行了订正，提高了模拟技巧。本项目的实施不仅为我国高温热浪的影响机制和季节预测提供大尺度背景和研究基础，研究的误差订正方法也应用在天津市和海河流域汛期降水预测中，取得较好效果。