Microscale and Mesoscale Structures in Convective Marine Boundary Layers

对流海洋边界层中的微尺度和中尺度结构

• 批准号: 9419927
• 负责人: Ernest Agee
• 金额: $ 34.57万
• 依托单位: Purdue Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-01-15 至 1998-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9419927&HistoricalAwards=false
• 关键词: Microscale; Mesoscale; Structures; Convective; Marine

9419927 Agee This grant will address the dynamic and thermodynamic properties and characteristics of convective marine boundary layers, through both observational study of special field data and theoretical model simulations. These cloud-topped boundary layers form in response to cold continental air masses that advect out over relatively warmer water, resulting in convective mixing and the formation of large polygonal arrays of mesoscale cellular convection that reside within the first one of two kilometers of the atmosphere. This convective pattern may exist as two- dimensional bands or streets, but often (downstream) resolves itself into three dimensional cells. During the past three decades a wealth of observational data for atmospheric convection studies has been accumulated from measurements by various means, including radar, aircraft, and satellites in special field observation programs. From the data, statistical parameters were obtained describing the structure and dynamics of the planetary boundary layers (PBL). These parameters are commonly computed in the form of temporal or spatial averages from a few (often from one) records of limited length, while theoretical studies operate with ensemble averages which assume averaging over an infinite number of realizations of random functions. Ensemble averages can be approximated by the averages taken over sufficiently large time or space segments only if the underlying random function is stationary (homogeneous). Current meteorological studies often result in statistically unreliable inference because of nonstationarity or inhomogeneity of data and inadequate averaging distances. For these reasons, under this project, data sets collected during several field programs will be revisited by employing a recently developed comprehensive statistical method that provides estimates of both statistical parameters and their statistical reliability. Large eddy simulation (LES) modeling is anoth er powerful tool that helps provide a theoretical understanding of the intricate fluid mechanics of atmospheric convection. Once again there is a problem of obtaining statistically reliable results, which will be addressed in this project by extending the above statistical method from random processes to random fields, and by approximating ensemble averages using Monte Carlo techniques. New LES model development of mesoscale convection in PBLs and proper statistical analysis of the LES model data will also be performed. The focus will be on the physical properties of convective PBLs with ice particles and snow precipitation. Model results will be compared with statistically reliable findings from field programs.

小行星9419927 该基金将通过对特殊领域数据的观测研究和理论模型模拟，解决对流海洋边界层的动力学和热力学性质和特征。 这些云顶边界层的形成是对大陆冷空气团的反应，这些冷空气团在相对温暖的水面上平流，导致对流混合和形成大的多边形阵列的中尺度细胞对流，这些细胞对流位于大气层的第一个两公里内。 这种对流模式可能以二维带状或街道形式存在，但通常（下游）将其自身分解为三维单元。 在过去的30年里，通过各种手段，包括雷达、飞机和特殊领域观测计划中的卫星，积累了丰富的大气对流研究观测数据。 从这些数据中，获得了描述行星边界层（PBL）的结构和动力学的统计参数。 这些参数通常以时间或空间平均的形式从有限长度的几个（通常是一个）记录中计算出来，而理论研究则采用系综平均，假设对随机函数的无限多个实现进行平均。 只有当潜在的随机函数是平稳的（齐次的）时，包络平均值才能近似于在足够大的时间或空间段上取的平均值。 目前的气象研究往往导致统计上不可靠的推断，因为非平稳或不均匀的数据和不适当的平均距离。 由于这些原因，在本项目下，将采用最近开发的综合统计方法重新审查在几个实地方案期间收集的数据集，该方法提供统计参数及其统计可靠性的估计数。 大涡模拟（LES）是另一个强有力的工具，有助于提供一个理论上的理解，复杂的流体力学的大气对流。 再次有一个问题，获得统计上可靠的结果，这将是解决在这个项目中，通过扩展上述统计方法从随机过程到随机场，并通过近似合奏平均使用蒙特卡洛技术。 还将对边界层中的中尺度对流进行新的LES模型开发，并对LES模型数据进行适当的统计分析。 重点将放在有冰粒和降雪的对流边界层的物理特性上。 模型结果将与实地方案的统计可靠结果进行比较。