全球海岸降水日变化的传播特征及其与重力波和密度流的联系

降水日变化是天气和气候的重要组成部分，地形下游或海岸附近的降水在夜间最大，呈现显著的相位传播特征，具有其复杂性。相比地形下游，由于观测条件限制，海岸降水日变化传播的特征和机制仍具有较大争议。前人针对特定海岸的研究发现重力波和密度流具有重要作用，但其具体关系和不同区域的相对贡献差异仍不十分清楚。本研究将从全球视野出发，理清全球各个主要海岸降水日变化传播特征的异同，及其对风场、湿度等环境因子的响应差异，结合对典型海岸的分析，阐明海岸日变化传播与重力波和密度流的联系。主要内容包括：1）从统计角度，利用卫星等观测研究全球海岸降水日变化传播特征的异同；2）基于观测和数值模拟，研究重力波和密度流等机制对日变化离岸传播的贡献；3）基于理想模拟和理论模型，研究不同主导机制下影响传播的关键因子及其相互作用。本研究将有助于提高对全球海陆气多尺度过程的认识和天气气候模式的模拟能力，具有重要的科学意义和社会价值。

The diurnal variation of rainfall is an important aspect of weather and climate. Precipitation near the coasts or mountains often reaches its peak at night, and is characterized by significant complex diurnal propagation. Compared to the leeside of mountains, diurnal variation of rainfall near the coasts are not well understood due to the limitation of observations. Previous studies on specific coasts have proposed that gravity waves and density currents play important roles, but their detailed relationships and differences in relative contributions in various coasts remain unclear. From a global perspective, we propose to clarify the similarities and differences in the characteristics of the diurnal rainfall propagation on all major coasts around the world, and distinguish responses of environmental factors in different areas such as background wind and moisture. With the further analysis of typical coasts, we elucidate the relationship between the coastal diurnal rainfall propagation and gravity waves or density currents. The main contents include: 1) from the perspective of statistical analysis, studying the similarities and differences in the propagation characteristics of global coastal diurnal rainfall propagation using satellites and other observations; 2) based on observations and numerical simulations, exploring the roles of gravity waves and density currents in offshore propagation of rainfall; 3) based on idealized simulations and theoretical models, examine the key factors that affect the coastal diurnal rainfall propagation and their interactions. This study will help improve the global understanding of multi-scale processes of land, sea, and air, and the capability of weather and climate models, which has important scientific significance and social value.