Dynamical Processes of Orographic Cumuli II

地形积云 II 的动力学过程

• 批准号: 0849225
• 负责人: Bart Geerts
• 金额: $ 47.6万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0849225&HistoricalAwards=false
• 关键词: Dynamical; Processes; Orographic; Cumuli; II

In the summer of 2006 a field campaign focused on orographic cumulus convection and boundary-layer circulations was conducted. The field campaign was called CuPIDO (Cumulus Photogrammetric, In-situ and Doppler Observations). This campaign deployed a unique combination of instruments, including an airborne cloud radar, atmospheric soundings, a surface mesonet, and stereo-photogrammetry. The present project involves further analysis of the CuPIDO dataset and builds on research completed in the initial two years following the field campaign.The main objective of the new research is to describe the observed fine-scale vertical and horizontal structure of the radar-observed cloud circulations and reflectivity fields within orographic cumuli congesti, and to use this in combination with flight-level measurements and other CuPIDO data to test the following key hypotheses: 1) Toroidal circulations surround the buoyant cores of growing cumuli. Significant entrainment occurs due to fine-scale instabilities at the updraft interface, and the mixed air is efficiently transferred to the cumulus core by the toroidal circulation, and 2) In places where a cumulus grows in the detritus of older clouds, its growth is enhanced, in particular at levels where the environment is dry (moisture-convection feedback hypothesis). The second objective is to use a high-resolution cloud-resolving model to statistically compare observed vs. modeled cumulus properties and patterns of entrainment and detrainment, and to use the continuous and dynamically consistent model output to assist in the interpretation of the observations, in particular regarding cumulus-environment interactions. The model will be used also in a more idealized way to assess the impact of ambient conditions (wind, wind shear, stable or dry layers) on the evolution of orographic (locked-source) convection.Intellectual Merit. In the past half-century several field studies of cumulus dynamics have been conducted by means of ground-based precipitation radars and aircraft making in situ measurements. The CuPIDO experiment places flight-level observations, collected while penetrating a cumulus, in the context of the radar-derived echo and velocity field, at a resolution of 40 m or better, in both vertical and horizontal planes. This combination constitutes a powerful tool for the study of fundamental cumulus dynamics. In particular, cloud radar data reveal entrainment events at various scales, and close-proximity aircraft data allow assessment of the thermodynamic and cloud microphysical characteristics of these events. The combination of the rich CuPIDO dataset with numerical modeling of orographic convection at resolutions matching that of the cloud radar will improve our understanding of characteristic cumulus properties and evolutions, the patterns and scales of entrainment, and mechanisms of cumulus-environment interaction. Broader impacts. Most warm-season precipitation results from deep convection. Cumulus convection operates over a range of horizontal and vertical scales, both over mountains and elsewhere. Not all scales can be resolved by operational numerical weather prediction models, now or in the foreseeable future. Parameterization of the effect of these unresolved cloud circulations on the larger-scale resolved circulations remains one of the greatest uncertainties in these models and also in climate models. Our analyses and numerical simulations of the fine-scale structure and evolution of cumuli, and of the interaction of cumuli with their environment, should lead to more accurate parameterization of the effects of cumulus convection on the resolved scales of these models.

2006 年夏天，开展了一次重点关注地形积云对流和边界层环流的实地活动。该实地活动被称为 CuPIDO（积云摄影测量、原位和多普勒观测）。这次活动部署了独特的仪器组合，包括机载云雷达、大气探测、表面介电网和立体摄影测量。目前的项目涉及对 CuPIDO 数据集的进一步分析，并建立在实地活动后最初两年完成的研究的基础上。新研究的主要目标是描述雷达观测云的观测到的精细尺度垂直和水平结构地形积云内的环流和反射率场，并将其与飞行高度测量和其他 CuPIDO 数据结合使用，以测试以下关键假设： 1) 环形环流围绕生长的浮力核心积云。由于上升气流界面处的细尺度不稳定性而发生显着的夹带，并且混合空气通过环形环流有效地转移到积云核心，并且 2) 在积云在较旧云的碎屑中生长的地方，其生长得到增强，特别是在环境干燥的水平上（水分对流反馈假设）。第二个目标是使用高分辨率云解析模型来统计比较观察到的与建模的积云特性以及夹带和脱出的模式，并使用连续且动态一致的模型输出来协助解释观测结果，特别是关于积云与环境的相互作用。该模型还将以更理想的方式用于评估环境条件（风、风切变、稳定层或干燥层）对地形（锁源）对流演化的影响。智力价值。在过去的半个世纪中，通过地面降水雷达和飞机现场测量进行了多项积云动力学现场研究。 CuPIDO 实验将在穿透积云时收集的飞行高度观测数据置于雷达产生的回波和速度场的背景下，在垂直和水平面上的分辨率均为 40 m 或更高。这种组合构成了研究基本积云动力学的强大工具。特别是，云雷达数据揭示了不同尺度的夹带事件，近距离飞机数据可以评估这些事件的热力学和云微物理特征。丰富的 CuPIDO 数据集与分辨率与云雷达相匹配的地形对流数值模拟相结合，将提高我们对特征积云特性和演化、夹带模式和规模以及积云与环境相互作用机制的理解。更广泛的影响。大多数暖季降水来自深层对流。积云对流在山脉和其他地方的一系列水平和垂直尺度上运行。现在或在可预见的将来，并不是所有尺度都可以通过可操作的数值天气预报模型来解决。这些未解析的云环流对更大规模解析环流的影响的参数化仍然是这些模型以及气候模型中最大的不确定性之一。我们对积云的精细尺度结构和演化以及积云与其环境相互作用的分析和数值模拟应该能够更准确地参数化积云对流对这些模型解析尺度的影响。