Abstract
The urban climatology consists not only of the urban canopy temperature but also of wind regime and boundary layer evolution among other secondary variables. The energetic input and response of urbanized areas is rather different to rural or forest areas. In this paper, we outline the physical characteristics of the urban canopy that make its energy balance depart from that of vegetated areas and change local climatology. Among the several canopy characteristics, we focus on the aspect ratio h/d and its effects. The literature and methods of retrieving meteorological quantities in urban areas are reviewed and a number of physical analyzes from conceptual or numerical models are presented. In particular, the existence of a maximum value for the urban heat island intensity is discussed comprehensively. Changes in the local flow and boundary layer evolution due to urbanization are also discussed. The presence of vegetation and water bodies in urban areas are reviewed. The main conclusions are as follows: for increasing h/d, the urban heat island intensity is likely to attain a peak around h/d≈4 and decrease for h/d>4; the temperature at the pedestrian level follows similar behavior; the urban boundary layer grows slowly, which in combination with low wind, can worsen pollution dispersion.
Highlights
Oke [1] describes the development of scientific inquiry into natural phenomena, in particular the urban meteorology, in four stages: (i) recognition and description of the phenomenon, (ii) linkage of the feature to other factors, (iii) study of processes causing the phenomenon, and (iv) construction of process–response models to predict the behavior of the phenomenon.Much has been done about stages (i) and (ii) in past decades
We are in a privileged moment in which many good urban meteorological databases have become available from field experiments, such as BUBBLE, DAPPLE, ESCOMPTE, JU2003
The so-called urban heat island effect directly affects the thermal comfort, whereas changes in the urban–rural or urban–suburban differential heating may cause an increasing of pollution and even changing the rain regime over large urban areas
Summary
Oke [1] describes the development of scientific inquiry into natural phenomena, in particular the urban meteorology, in four stages: (i) recognition and description of the phenomenon, (ii) linkage of the feature to other factors, (iii) study of processes causing the phenomenon, and (iv) construction of process–response models to predict the behavior of the phenomenon. Along with the growth of available data, many urban models, especially those aiming to simulate energy/momentum/mass balance, are from that period. These databases have made possible the approach of stages (iii) and (iv). We review how key features of urban canopies distinguishes them from rural or forest areas and how they impact the local climate. Building-street aspect ratio (Section 4); Presence of vegetation (Section 5.1); Presence of water bodies (Section 5.2) All of these factors can impact the energetics of an urban area. Understanding their mechanisms of action can aid city planners to design more sustainable and enjoyable cities. The so-called urban heat island effect directly affects the thermal comfort, whereas changes in the urban–rural or urban–suburban differential heating may cause an increasing of pollution and even changing the rain regime over large urban areas
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