Dynamical Processes of Orographic Cumuli

地形积云的动力学过程

• 批准号: 0444254
• 负责人: Bart Geerts
• 金额: --
• 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: 2005
• 资助国家: 美国
• 起止时间: 2005-11-15 至 2009-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0444254&HistoricalAwards=false
• 关键词: Dynamical; Processes; Orographic; Cumuli

This research is part of the CuPIDO (Cumulus Photographic Investigation and Doppler Observations) project. This campaign, to be conducted in the summer of 2006, intends to describe early cumulus development over the Santa Catalina Mountains in Arizona at the meso-gamma and cloud scales, with an emphasis on boundary-layer evolution and the effects of entrainment, detrainment, and glaciation on individual convective towers that may develop in succession and culminate in the cumulonimbus stage. This research will utilize an advanced airborne cloud radar (Wyoming Cloud Radar; WCR) and in situ aircraft thermodynamic measurements. The project will be collaborative with a University of Arizona scientist who will apply newly developed techniques in digital stereo-photogrammetry. The geo-located cloud-edge maps, inferred from the digital stereo-images, will complement the WCR observations since the cloud base and the earliest stages of cumulus development cannot be detected by the radar. The primary objective is to describe the radar echo and kinematic structure and evolution of cumuli at an entrainment-resolving scale, and to merge this description with in situ cloud and thermodynamic data, in order to gain new insights into the fundamental dynamical processes controlling the growth and decay of cumulus congestus. In this context, the mountains provide a natural laboratory, given the regular, repetitive, and geographically fixed development of cumuli. The secondary objective specifically deals with the orographic forcing of cumulus clouds. The spatial and temporal changes in the environment in which orographic cumuli develop and decay will be studied in order to gain insights into the synergy between deep cumulus convection and orographically-induced mesoscale circulations. In the past half-century several field studies of cumulus dynamics have been conducted by means of aircraft making in situ measurements, and by means of ground-based precipitation radars. These studies form the basis of current conceptual representations of entrainment; however, entrainment remains the least understood factor in cumulus development. Newly developed technology provides the ability to place flight level observations, collected while penetrating a cumulus, in the context of radar-derived echo and velocity field at a resolution of 40 m or better. This combination constitutes a powerful tool for the study of fundamental cumulus dynamics. In particular, the WCR reveals entrainment events at various scales in the airflow and echo fields. Close proximity aircraft data allow assessment of the thermodynamic and cloud microphysical characteristics of these events. Cumulus convection operates at a range of horizontal and vertical scales and these scales are not resolved by operational numerical weather prediction (NWP) models. Thus the simulation of its impact is challenging, and cumulus parameterization remains one of the greatest uncertainties in NWP models and general circulation models (GCMs). New generation operational NWP models may resolve mesoscale orographic circulations, but the effect of cumulus convection will remain in need of parameterization. Observations of the fine-scale structure and evolution of cumuli, and the resulting new insights into the fundamental dynamical processes of cumuli interacting with their environment, should lead to a more accurate parameterization of the overall effect of cumulus convection on the resolved scales of NWP models and GCMs.

这项研究是 CuPIDO（积云摄影调查和多普勒观测）项目的一部分。 这项活动将于 2006 年夏天进行，旨在描述亚利桑那州圣卡塔利娜山脉上空的中伽玛和云尺度的早期积云发展，重点是边界层演化以及夹带、滞留、个别对流塔上的冰川作用可能会连续发展并在积雨云阶段达到顶峰。 这项研究将利用先进的机载云雷达（怀俄明云雷达；WCR）和现场飞机热力学测量。 该项目将与亚利桑那大学的一位科学家合作，该科学家将在数字立体摄影测量中应用新开发的技术。 由于雷达无法探测到云底和积云发展的最早阶段，从数字立体图像推断出的地理定位云边缘图将补充 WCR 观测结果。 主要目标是在夹带分辨尺度上描述积云的雷达回波和运动学结构和演化，并将这种描述与原位云和热力学数据合并，以便获得对控制积云生长的基本动力学过程的新见解和浓积云的衰变。 在这种背景下，考虑到积云的规律性、重复性和地理固定发展，山脉提供了一个天然的实验室。第二个目标专门涉及积云的地形强迫。 将研究地形积云发展和衰变环境的时空变化，以深入了解深积云对流与地形引起的中尺度环流之间的协同作用。在过去的半个世纪中，通过飞机现场测量和地面降水雷达进行了多项积云动力学现场研究。 这些研究构成了当前夹带概念表征的基础；然而，夹带仍然是积云发展中最不为人所知的因素。 新开发的技术能够将穿透积云时收集的飞行高度观测结果置于雷达回波和速度场的背景下，分辨率为 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，WCR 揭示了气流和回声场中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。积云对流在一系列水平和垂直尺度上运行，而这些尺度无法通过数值天气预报 (NWP) 模型来解析。 因此，对其影响的模拟具有挑战性，积云参数化仍然是 NWP 模型和大气环流模型 (GCM) 中最大的不确定性之一。 新一代数值天气预报业务模型可能会解决中尺度地形环流问题，但积云对流的影响仍需要参数化。 对积云精细尺度结构和演化的观测，以及由此产生的对积云与其环境相互作用的基本动力学过程的新见解，应该能够更准确地参数化积云对流对 NWP 模型解析尺度的总体影响和 GCM。