The impact of urban areas on weather

• Published in: Quarterly journal of the Royal Meteorological Society Vol. 132; no. 614; pp. 1 - 25
• Main Author: Collier, C. G.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2006; Wiley
• Subjects: Boundary layer; Convection, turbulence, diffusion. Boundary layer structure and dynamics; Doppler lidar; Earth, ocean, space; Exact sciences and technology; External geophysics; Heat island; Meteorology; Turbulence Urban meteorology; Urban precipitation; Thermal island; aerosols; Ground based measurement; Space remote sensing; energy transfer; turbulent flow; Satellite observation; urban areas; Measurement in situ; Radar remote sensing; Air flow; Micrometeorology; Complex terrain; Atmospheric boundary layer; Boundary layer Doppler lidar Heat island Turbulence Urban meteorology Urban precipitation; Lidar; Effect on climate; Doppler radar; Microclimatology
• ISSN: 0035-9009; 1477-870X
• DOI: 10.1256/qj.05.199

The industrial revolution led to a rapid development of urban areas. This has continued unremittingly over the last 200 years or so. In most urban areas the surface properties are heterogeneous, which has significant implications for energy budgets, water budgets and weather phenomena within the part of the earth's atmosphere that humans live. In this paper I discuss the structure of the planetary boundary layer, confining our analysis to the region above the rooftops (canopy layer) up to around the level where clouds form. It is in this part of the atmosphere that most of the weather impacting our lives occurs, and where the buildings of our cities impact the weather. In this review, observations of the structure of the urban atmospheric boundary layer are discussed. In particular the use of Doppler lidar provides measurements above the canopy layer. The impact of high‐rise buildings is considered. Urban morphology impacts energy fluxes and airflow leading to phenomena such as the urban heat island and convective rainfall initiation. I discuss in situ surface‐based remote sensing and satellite measurements of these effects. Measurements have been used with simple and complex numerical models to understand the complexity and balance of the interactions involved. Cities have been found to be sometimes up to 10 degC warmer than the surrounding rural areas, and to cause large increases in rainfall amounts. However, there are situations in which urban aerosol may suppress precipitation. Although much progress has been made in understanding these impacts, our knowledge remains incomplete. These limitations are identified. As city living becomes even more the norm for large numbers of people, it is imperative that we ensure that urban effects on the weather are included in development plans for the built environment of the future. Copyright © 2006 Royal Meteorological Society