Working group report Relations between scale, model approach and model parameters

Abstract

This chapter presents a report on relations among scale, model approach, and model parameters. A model can be defined as a simplified representation of nature or a system that can be used, inter alia , to improve the understanding of processes or to simulate and evaluate the response to an imposed forcing. Models can be classified in various ways—that is, according to discipline (physics, biology, chemistry, or economy), to scale (molecular, micro-scale, measurement scale, field scale, regional, or global), or according to their mathematical nature. The chapter focuses on scaling trace gas exchanges between terrestrial and aquatic systems and the atmosphere. It presents a number of examples that are instructive for the problems encountered in dealing with the scaling issue. These examples illustrate the intimate relationship between scale and the model approach chosen. The chapter discusses the rationale of adopting a certain scale and evaluates the use of models in up- and down-scaling, emphasizing the balance between required detail and feasibility of validation and computation. A comparison of scaling problems inherent to marine and terrestrial ecosystems is also provided.