洋面暖云微物理结构及暖云降水过程的卫星观测研究

Oceanic warm clouds pose predominant contribution to the overall shortwave albedo of the system of earth and atmosphere. They are also closely correlated with aerosols within the atmospheric boundary layer and actively interact with each other. Given these distinctive features, oceanic warm clouds are among the important factors in the climate feedback system, and form a main source of the uncertainties in the climate projection. However, so far the understanding on microphysical structures of warm clouds, which fundamentally determine their radiative effects, are still very limited. It is also not very clear about the characteristics of warm rain that are mostly modified by the microphysical processes. Cloud-resolving numerical simulations are an important way for exploring the microphysical features of warm clouds. But such methods generally suffer from the extremely limited paths that are used to acquire initial and boundary conditions. Thus the representativeness of those simulation results are actually restricted. Focusing on the abovementioned issues, the present study would devote to get new insights into the microphysical features of oceanic warm clouds on the global scale by using the advanced measurements from multiple spaceborne sensors that are currently in orbit. The high-quality data of cloud and precipitation parameters that are jointly retrieved from active and passive measurements would be employed to resolve the warm cloud microphysics and the associated warm rain processes. The typical differences of vertical structures of microphysical parameters between non-raining and raining warm clouds would be revealed. Special attentions would be paid to the onset of rain event, and the microphysical structures in this critical stage would be explored. Also the varying characteristics of microphysical structures during the entire cycle of warm rain that contains both development and dissipation phases would be specifically clarified. The results would help to construct the systematic knowledge about the microphysical features of oceanic warm clouds as well as the regime of associated warm rain, and are probably beneficial to relevant studies like cloud radiative effects and cloud-climate feedback.

洋面暖云在全球短波反照率中占据主导贡献，同边界层气溶胶存在密切的相互作用，是气候反馈系统中最重要的因子之一，也是当前气候模拟不确定性的最主要来源。然而至今对于从根本上决定暖云辐射效应的微物理结构，以及对于由微物理过程主导的暖云降水还缺乏充分了解。云分辨数值模拟作为目前开展暖云微物理研究的主要方式，其初始及边界条件的获取途径非常受限，模拟结果的代表性明显不足。本项目拟利用当前最先进的星载传感器所提供的多源同步观测资料，凭借结合主被动探测的高质量云参数及降水反演数据，从观测角度在全球范围认识洋面暖云的微物理特性。明确降水暖云与非降水暖云在微物理参数垂直结构上的典型差异，揭示洋面暖云降水生成阶段的微物理结构特征，以及降水发展过程中所伴随的暖云微物理结构演化规律。研究结果有助于建立对洋面暖云微物理特性的系统认识，为深入理解暖云降水机制提供事实依据，也将为云辐射效应以及云气候反馈等相关研究提供参考。

洋面暖云在行星反照率中占据主导贡献，同边界层气溶胶存在密切的相互作用，是气候反馈系统中最重要的因子之一，也是当前气候模拟不确定性的最主要来源。然而由于观测资料的缺乏，至今对于从根本上决定暖云辐射效应的微物理结构，以及对于由微物理过程主导的暖云降水还缺乏充分了解。.本项目使用A-Train卫星系列多平台合成资料，以积云、层积云、层云、高积云等四类典型洋面低空暖云为对象，关注其微物理结构及降水特征，主要取得了以下几方面的成果。1）系统分析了洋面暖云发生频率的全球分布规律以及暖云降水的频率和强度特征，揭示了洋面降水暖云与非降水暖云在水平尺度、云顶高度、云层厚度、光学厚度、云水路径等宏观物理参数上的典型差异。2）结合星载雷达廓线及辐射成像仪反演资料，揭示了降水暖云与非降水暖云的云滴数密度、云滴有效半径及云水含量等微物理参数的垂直结构特征，明确了两类暖云在微物理结构上的静态统计差异。3）分析了暖云中雨滴形成关键期所对应的云滴数密度、云滴有效半径、云水含量的垂直结构特征，考察了暖云微物理参数在降水发展阶段的变化特征及其相互间的动态相关。这些结果促进了对洋面低云系生消机制及其降水过程的理解，可为改善暖云降水卫星反演算法以及改进数值模式中低云气候反馈机制提供参考。.项目在执行期内基本完成了既定目标，研究成果发表期刊论文5篇、国际会议论文2篇，依托本项目培养博士2人、硕士2人，其中3人即将于今年毕业。