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，旨在描述早期积云的发展，在中伽马和云尺度的亚利桑那州的圣卡塔利纳山脉，重点是边界层的演变和夹带的影响，疏散，和冰川对个别对流塔，可能会发展在连续和最终的积雨云阶段。 这项研究将利用先进的机载云雷达（怀俄明州云雷达; 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，他将在数字立体摄影测量中应用新开发的技术。 从数字立体图像推断的地理定位云边缘图将补充WCR观测，因为雷达无法探测到云底和积云发展的最早阶段。 主要目标是描述雷达回波和运动学结构和积云的演变在一个清晰的尺度，并合并这种描述与现场云和热力学数据，以获得新的见解的基本动力学过程控制的积云congestus的增长和衰减。 在这种情况下，山脉提供了一个天然的实验室，因为积云的发展是有规律的，重复的和地理上固定的。第二个目标专门处理积云的地形强迫。 地形积云的发展和衰减的环境中的空间和时间的变化进行了研究，以深入了解深积云对流和地形引起的中尺度环流之间的协同作用。在过去的半个世纪里，已经通过飞机现场测量和地面降水雷达进行了几次积云动力学的实地研究。 这些研究形成了当前卷吸概念表述的基础;然而，卷吸仍然是积云发展中最不了解的因素。 新开发的技术提供了将穿透积云时收集的飞行高度观测值置于分辨率为40米或更高的雷达回波和速度场范围内的能力。 这种组合构成了一个强有力的工具，为基础积云动力学的研究。 特别是，WCR揭示夹带事件在不同尺度的气流和回波场。 近距离的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，这些尺度不能通过业务数值天气预报（NWP）模式来解决。 因此，其影响的模拟是具有挑战性的，积云参数化仍然是NWP模式和大气环流模式（GCM）中最大的不确定性之一。 新一代业务数值预报模式可以解决中尺度地形环流，但积云对流的影响将仍然需要参数化。 积云的细尺度结构和演变的观测，以及由此产生的积云与环境相互作用的基本动力学过程的新见解，应该导致一个更准确的参数化的积云对流的整体效果上解决尺度的数值预报模式和GCM。