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.

在2006年夏天，进行了一场野外运动，重点是集市对流和边界循环。现场运动称为丘比特（Cumulus摄影测量，原位和多普勒观测值）。这项运动部署了独特的乐器组合，包括空气中的云雷达，大气响起，表面介质和立体声图。 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 horizo​​ntal 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循环围绕着成长的库利的浮力核心。由于在上升气流界面处的细尺度不稳定性而发生了重大夹带，并且混合空气通过环形循环有效地转移到了积云核心上，而2）在较旧云的碎屑中成长的地方，其生长增长，尤其是在环境干燥的水平（湿度为干燥反应反馈反馈）的水平上。第二个目标是使用高分辨率的云解析模型在统计上比较观察到的与建模的积云和夹带和损坏的模式，并使用连续且动态的模型输出来帮助解释观测值，特别是关于积木环境的相互作用。该模型还将以更理想的方式使用，以评估环境条件（风，风剪，稳定或干层）对地形（锁定源）对流的演变的影响。在过去的半个世纪中，积云动力学的几项现场研究是通过基于地面的沉淀雷达和飞机进行原位测量进行的。丘比特实验将飞行水平的观测值放置在雷达衍生的回声和速度场的背景下，在垂直和水平平面中以40 m或更好的分辨率进行了渗透积云。这种组合构成了研究基本积云动力学的强大工具。特别是，云雷达数据揭示了各种尺度的夹带事件，近距离飞机数据允许评估这些事件的热力学和云微物理特征。在与云雷达相匹配的决议上，丰富的丘比特数据集与地形对流的数值建模的组合将提高我们对特征性积云特性和演变的理解，夹带的模式和尺度以及库卢斯 - 环境相互作用的机制。更广泛的影响。大多数温暖的降水是由深对流引起的。积云对流在山和其他地方的一系列水平和垂直尺度上运行。并非所有量表都可以通过现在或可预见的将来通过操作数值天气预测模型来解决。这些未解决的云循环对大规模解析循环的效果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Cumuli的精细结构和演变以及Cumuli与环境的相互作用的分析和数值模拟应导致Cumulus对流对这些模型分辨率尺度的影响的更准确的参数化。