Parameterization of urban characteristics for global climate modeling

To help understand potential effects of urbanization on climates of varying scales and effects of climate change on urban populations, urbanization must be included in global climate models (GCMs). To properly capture the spatial variability in urban areas, GCMs require global databases of urban extent and characteristics. This article describes methods and characteristics used to create a data set that can be utilized to simulate urban systems on a global scale within GCMs. The data set represents three main categories of urban properties: spatial extent, urban morphology, and thermal and radiative properties of building materials. Spatial extent of urban areas is derived from a population density data set and calibrated within thirty-three regions of similar physical and social characteristics. For each region, four classes of urbanization are identified and linked to a set of typical building morphology, thermal, and radiative characteristics. In addition, urban extent is simulated back in time to 1750 based on national historical population and urbanization trends. A sample set of simulations shows that the urban characteristics do change urban heat island outcomes. In general the simulations show greater urban heat islands with increasing latitude, in agreement with observations. [Supplemental material is available for this article. Go to the publisher's online edition of Annals of the Association of American Geographers for the following free supplemental resource: (1) a table of the Global Data Set of Urban and Building Properties © 2007-2009.]