RELATIONS BETWEEN SCALE, MODEL APPROACH

摘要: Many scientific problems and environmental issues are posed or occur at temporal and spatial scales that cannot be covered by direct measurements or experiments. Relevant spatial scales may vary from micrometers for microbial processes to the global scale for atmospheric processes (ie almost 14 orders). Similarly, the dynamics of reactive gases occur within much shorter time scales than that of a relative non-reactive gas, such as carbon dioxide. Moreover, components may show variability at various time and spatial scales. For instance, carbon dioxide exhibits not only diel (light/dark) and seasonal variability, but also interannual (eg ENSO events) and longer-term variations. There is also a relation between the temporal and spatial scales of interest, but it is not necessarily linear. The various scales may overlap, but often there are significant gaps. Mathematical modelling is one way of attempting to bridge between scales.A model can be defined as a simplified representation of nature or a system that can be used, inter alia, to improve our understanding of processes or to simulate and evaluate the response to an imposed forcing. Depending on the accuracy and precision wanted and the level of detail required, models can be formulated to operate at various scales. As an example, a geographical map for an aircraft pilot contains much less detail of the landscape than that for a car driver, whereas that for a hiker contains even more detail. Nevertheless they serve the same function (navigation) and are just made to cover the appropriate scale. Models can be classified in various ways, ie according to discipline (physics, biology, chemistry …