湍流微气象观测的印痕分析方法及其应用拓展

Footprint Analysis in Micrometeorology and Its Extended Applications

在地面与大气间湍流相互作用的研究工作中,印痕(footprint)与印痕分析发挥着越来越重要的作用。文中介绍微气象学意义下印痕与印痕分析的理论、方法、历史和最新研究进展。着重介绍了具有理论和实用意义的数学解析印痕模型和拉格朗日数值印痕模型。对印痕分析在实际工作中的应用与问题进行了评述。文中明确指出了印痕概念的三维空间性质,探讨了将印痕分析从微气象学范畴拓展到中尺度范围的可能性,及其在大气环境问题研究中的意义。

Footprint analysis plays a more and more important role in research of turbulent exchange between land surface and the atmosphere. A review is given to introduce the theory, method, history and recent development on footprint in the micrometeorological view. The mathematically analytical footprint models and Lagrangian numerical footprint models are emphasized since their theoretical and applicable significance. Application and problems of the footprint method in practical usage of research are addressed. Analytical footprint models are still widely used in practice since their simplicity. However their presumption on horizontal homogeneous surface is worthy of notice, since the presumption could be a limitation when applying the method to non-homogeneous condition. Lagrangian footprint models are more flexible in applying to non-homogeneous surfaces, though detailed turbulence and flow field as inputs may be required. Technical advances of backward Lagrangian footprint modeling are noticed, as well the differences and comparison of the backward method to its forward counterpart. Three aspects of application of footprint analysis are pointed out, i. e. , （1） interpretation of experimental data, particularly the turbulent flux data; （2） quality control of the experiment data; （3） instruction on field experiment design. Additional aspects relevant to footprint and its application are also addressed. Those are, the plume invert assumption usually used with a forward dispersion method in footprint analysis; the urgent need for validation of footprint models; the identification of the meaning of footprint as ＂potential source area＂ rather than ＂source area＂; the difference between units of a flux footprint and a concentration footprint. Extension of the footprint concept into three-dimensional in space is discussed. Traditionally the footprint is presumed merely two-dimensional over ground surface. At last, it is discussed the possibility of extending the application of footprint from micrometeorological view into meso-scale view. In research of atrnospheric environment or air quality issues, it is significant to analyze the representative of monitoring data at local or even regional scales. Footprint, particularly the concentration footprint, may be utilized as a useful tool in those problems.Examples of preliminary results on applying footprint analysis to meso-scale situations are presented.