Collaborative Research: Physics of Stratocumulus Top (POST)

合作研究：层积云顶部物理学（POST）

• 批准号: 0736072
• 负责人: Qing Wang
• 金额: $ 5.01万
• 依托单位: Naval Postgraduate School
• 依托单位国家: 美国
• 项目类别: Interagency Agreement
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0736072&HistoricalAwards=false
• 关键词: Collaborative; Research; Physics; Stratocumulus; Top

Stratocumulus clouds (Sc) off the west coast of California will be studied using a combination of aircraft measurements and modeling. The objective is to improve the understanding of the physical processes that occur near Sc top, and that influence the cloud-top entrainment process and overall boundary-layer evolution. These processes include wind shear, entrainment rate, CTEI (cloud-top entrainment instability), solar and infrared radiation, hydrometeor and CCN (cloud condensation nuclei) effects, and the formation and role played by the EIL (entrainment interface layer). The study is a combination of field measurements and modeling. For the former, the CIRPAS Twin Otter research aircraft will be deployed out of Monterey for ~20 flights in Sc. It will carry a full complement of sensors to produce measurements related to these physical processes. Sensors include the UFT (ultra-fast temperature probe), PVM (fast particulate volume monitor), fast Lyman-Alpha hygrometer, PDI (phased Doppler interferometry probe), other droplet probes, gust probe, solar and infrared radiometers, and the standard set of Twin-Otter probes recording meteorology and aircraft operating properties. The aircraft will be deployed primarily in fields of unbroken Sc with an emphasis on porpoising maneuvers vertically above, through, and below the Sc top level to detect fine-scale changes in conditions. Boundary layer profiles and near-surface horizontal legs will be flown to deduce flux profiles through the sub-cloud boundary layer. NexSat and CloudSat products will be compared to aircraft measurements in real-time and used to help vector the aircraft to fields of Sc. The analysis phase of the field study includes comparisons between the measured physical processes and the calculated cloud-top entrainment velocities with the purpose of clarifying the influence of various processes on the entrainment velocities. The modeling phase of the study will cover a wide range of scales associated with these physical processes. The LEM (linear eddy model) looks at the finest scales associated with droplet size changes. New fine-scale LES (large-eddy simulation) will be applied with grid resolution comparable to the several-meters scale associated the expected typical entrained parcel size. A mesoscale model (COAMPS) will be used to study the larger-scale behavior of the Sc and the boundary layer, and also will be used in real-time to provide predictions for deploying the aircraft. Parameterizations of the cloud top entrainment velocity will be evaluated and improved. The intellectual merit of the project will be improved prediction of the behavior and evolution of Sc found over large areas of the sub-tropical oceans. This has proved to be difficult because of the imperfect understanding of the physical processes involved and the inability to measure them accurately. High on the priority list for better understanding is the entrainment process. The literature shows a lack of measurement success and predictive capability for this important process that affects Sc lifetime. This study uses a unique combination of aircraft measurements and modeling to focus on this deficiency. For the first time co-located high-rate microphysical, thermodynamic, and turbulence probes are used on a fixed-wing aircraft deployed for unraveling the physical interactions near Sc top. Broader impacts derive from this improved understanding of Sc behavior and evolution will be the ability to predict the behavior of low-level stratocumulus found over large ocean areas. This is needed given their major contribution to the planetary albedo that affects the planetary radiation balance and thus global warming.

将结合飞机测量和建模来研究加利福尼亚州西海岸的层积云 (Sc)。目的是提高对 Sc 顶部附近发生的物理过程的理解，这些过程影响云顶夹带过程和整体边界层演化。这些过程包括风切变、夹带速率、CTEI（云顶夹带不稳定性）、太阳和红外辐射、水凝结和CCN（云凝结核）效应以及EIL（夹带界面层）的形成和所起的作用。该研究结合了现场测量和建模。对于前者，CIRPAS 双水獭研究飞机将部署在蒙特利以外的地方，在 SC 进行约 20 次飞行。它将携带全套传感器来产生与这些物理过程相关的测量结果。传感器包括 UFT（超快速温度探头）、PVM（快速颗粒物体积监测仪）、快速 Lyman-Alpha 湿度计、PDI（相控多普勒干涉测量探头）、其他液滴探头、阵风探头、太阳和红外辐射计以及标准套件双水獭探测器记录气象和飞机运行特性。该飞机将主要部署在未破坏的 SC 区域，重点是在 SC 顶层垂直上方、穿过和下方进行海豚式机动，以检测条件的精细变化。将飞行边界层剖面和近地表水平腿，以推断通过云下边界层的通量剖面。 NexSat 和 CloudSat 产品将与飞机测量进行实时比较，并用于帮助将飞机引导到 Sc 区域。现场研究的分析阶段包括将测量的物理过程与计算的云顶夹带速度进行比较，以明确各种过程对夹带速度的影响。研究的建模阶段将涵盖与这些物理过程相关的广泛范围。 LEM（线性涡流模型）着眼于与液滴尺寸变化相关的最精细尺度。新的精细尺度 LES（大涡流模拟）将采用与预期典型夹带地块尺寸相关的几米尺度的网格分辨率。中尺度模型（COAMPS）将用于研究 Sc 和边界层的更大规模行为，并将用于实时提供飞机部署的预测。将评估和改进云顶夹带速度的参数化。该项目的智力价值将改进对副热带海洋大片地区发现的钪行为和演化的预测。事实证明，这是很困难的，因为对所涉及的物理过程的理解不完善，并且无法准确地测量它们。为了更好地理解，优先考虑的是夹带过程。文献表明，对于影响 Sc 寿命的这一重要过程，缺乏成功的测量和预测能力。 这项研究采用了飞机测量和建模的独特组合来关注这一缺陷。首次在固定翼飞机上使用并置的高速微物理、热力学和湍流探测器，用于解开 Sc 顶部附近的物理相互作用。对 Sc 行为和演化的进一步了解将带来更广泛的影响，即预测大片海洋区域低层层积云行为的能力。鉴于它们对影响行星辐射平衡并进而影响全球变暖的行星反照率的重大贡献，这是必要的。