Dynamics of Altocumulus Clouds

高积云的动力学

• 批准号: 0239982
• 负责人: Vincent Larson
• 金额: $ 24.03万
• 依托单位: University of Wisconsin-Milwaukee
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-02-01 至 2007-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0239982&HistoricalAwards=false
• 关键词: Dynamics; Altocumulus; Clouds

Though less studied than high-level cirrus or low-level stratocumulus clouds, mid-level altocumulus clouds are estimated to cover 22% of the earth's surface and to be important for understanding the planetary radiation balance. They are characterized by distinctive physical processes, which include (1) entrainment into both cloud base and cloud top; (2) maintenance by large-scale vertical motions; (3) the frequent presence of both ice and liquid phases. This project is aimed at studying two aspects of altocumulus clouds: the mechanisms responsible for their dissipation and the factors affecting the horizontal variability of their structure. Modes of inquiry include large-eddy simulation (LES), theory, and data analysis. Observations used for validating the simulations are from the Complex Layered-Cloud Experiment (CLEX) of 1999. The aim of the simulations is to evaluate the relative importance of four processes that lead to cloud dissipation: large-scale subsidence, radiative heating, entrainment drying, and precipitation fallout. The LES is carried out using a Beowulf cluster of 22 personal computers running the Regional Atmospheric Modeling System (RAMS) model with an advanced treatment of microphysics. Findings of the research bear on both climate modeling and remote sensing of cloud properties.

虽然比高层卷云或低层积云研究得少，但据估计，中层高积云覆盖了地球表面的22%，对于理解行星的辐射平衡很重要。它们的特点是独特的物理过程，包括(1)夹带进入云底和云顶；(2)通过大范围垂直运动维持；(3)经常存在冰和液体。本项目旨在研究高积云的两个方面：造成高积云消散的机制和影响其结构水平变化的因素。研究模式包括大涡模拟(LES)、理论和数据分析。用于验证模拟的观测数据来自1999年复杂的分层云实验(CLEX)。模拟的目的是评估导致云消散的四个过程的相对重要性：大范围下沉、辐射加热、夹带干燥和降水散落。LES是使用由22台个人计算机组成的Beowulf集群进行的，该集群运行具有先进微物理处理的区域大气建模系统(RAMS)模型。这项研究的结果涉及气候建模和云层特性的遥感。