Field observations and physical models may be used to investigate pollutant transportation and dispersion within urban canyons and validate numerical models . on the other hand , validated numerical models are often applied to simulate in detail atmospheric dispersion within the urban canopy . the numerical results in combination with physical model and or field data may be used to assess urban air quality and support decision ? ? making for pollution control strategies and traffic planning 外场观测和物理模拟可以考察街谷内污染物的传输扩散规律并对数值模式进行检验，另外，复杂的数值模式则可对城市冠层内大气扩散问题进行详细模拟，数值模拟和外场观测及物理模拟相配合，可用于环境质量评价污染控制决策及交通规划。
