ABSTRACT
Urban areas create distinct local and micro-scale climates. Commonly cited effects are presented in Table 10.1. What this summary does not make clear, however, is that urban climates vary significantly both within and between cities. Urban climates result from changes in the nature of the urban surface (the materials, its morphology, the fraction of built and vegetated cover, etc.) and the activities of the cities’ inhabitants (generating heat, greenhouse gases, aerosols, etc.) as they move around, work and live in the city. Ultimately urban climates are due to the surface-atmosphere exchanges of energy, mass and momentum (represented conceptually in Figure 10.1). Understanding these exchanges, and the effects of a particular urban setting on their spatial and temporal dynamics, are key to understanding urban climates at the scale of the city, neighbourhood or individual street or property level, and to predicting and mitigating negative effects. This chapter describes these energy and mass exchanges and highlights key urban controls with data and examples of studies that document effects.
