Modeling of Contaminant Dispersion in Complex-Terrain Flows

本研究已提交至环境地球化学和生物化学（EGB）征求NSF 96-152。本研究计划的目的是利用实验室实验人员、湍流建模人员、数值分析人员和实地观测人员的互补专业知识，在崎岖（复杂）地形中开展空气流动和污染物扩散的跨学科研究，包括化学和物理转化。由于有限的垂直混合、夜间降温时的空气汇集以及缺乏背景中尺度风流冲刷盆地，复杂地形下的城市发展容易出现严重的空气污染问题。影响当地风流的重要地表特征通常在100米量级，而山谷的日空气运动则由100公里以上的尺度控制。这些尺度差异给数值模型带来了难题。此外，在早晨和晚上从地面的冷却到加热的过渡期间，反之亦然（周转或过渡时期），风的运动是间歇性的，风速约为每秒一米，因此给现场测量带来了问题。已知用于预测这些地区的流量和分散的现有模型的结果不能令人满意，特别是在周转期间。拟议的工作将主要针对开发一个强大的、通用的、复杂地形流动的地球化学物理数值模型及其验证。将进行实验室和理论研究，以提高对复杂地形，非平衡湍流的基本理解和发展新的参数化。在选定地点每隔10分钟采集的粒子样本的详细分析将用于湍流参数化的验证和气溶胶模型的发展。现有的气象模式将被显著修改，以纳入这些新的参数化，包括非定常垂直混合、气溶胶输送和化学。这种新的复杂地形模型将根据现有的和新的现场数据进行测试和校准。采用适当比例的室内复杂地形模型，推导出过渡性低风期的风场；为此，将使用亚利桑那州凤凰城的物理模型。数值模型将在特定区域运行——具有现实的初始和边界条件以及源分布——用于风场、污染物水平、对土壤的影响、室内和室外空气之间的相互作用以及对人类暴露的评估。

ABSTRACT CTS-9708452 FERNANDO This proposal was submitted to the environmental Geochemistry and Biochemistry (EGB) solicitation NSF 96-152. The aim of this research program is to utilize the complementary expertise of laboratory experimentalists, turbulence modelers, numerical analysts and field observationalists to carry out an interdisciplinary study of air flow and pollutant dispersion, including chemical and physical transformations, in rugged (complex) terrain. As a result of restricted vertical mixing, pooling of air during nocturnal cooling and absence of background meso-scale wind flow to flush the basins, urban developments in complex terrain are prone to severe air pollution problems. Often the important surface features which influence the local wind flows are of the order of 100 meters while the valley diurnal air motions are governed by scales of more than 100 km. These scale disparities pose a difficult problem for numerical models. In addition, during morning and evening transitions from cooling to heating of the ground and vice-versa (turnover or transitional periods), wind motions are intermittent with wind speeds of the order of one meter per second, thus posing problems for field measurements. The existing models for the prediction of flow and dispersion in these areas are known to yield unsatisfactory results, especially during turnover periods. The proposed work will be directed primarily toward the development of a robust, general-purpose, geo-chemo-physical numerical model for complex-terrain flows and its validation. Laboratory and theoretical studies will be conducted to improve the fundamental understanding of and develop new parameterizations for complex-terrain, non-equilibrium turbulent flows. Detailed analyses of particle samples taken in selected field sites at 10 minute intervals will be used for the validation of turbulence parameterizations and the development of an aerosol model. An available meteorological model will be significantly m odified to incorporate these new parameterizations, including unsteady vertical mixing and aerosol transport and chemistry. This new complex-terrain model will be tested and calibrated against available and new field data. The wind fields during transitional low-wind periods will be deduced by using properly scaled laboratory complex-terrain models; a physical model of the Phoenix, Arizona area will be used for this purpose. The numerical model will be run for specific areas -- with realistic initial and boundary conditions and source distribution -- for operational forecasting of wind fields, pollutant levels, impacts on soil, interaction between indoor and outdoor air and assessment of human exposure.