typically much rougher and drier than rural surfaces. In addition, the three-dimensional nature of urban environments affects a number of parameters such as evaporation rates, absorption and reflection of solar radiation, and storage of heat, as well as wind and turbulence fields (Figure 3.2). Gaseous and particulate matter emissions (Figure 3.3) also may contribute to land-atmosphere interactions. Classifications for urban land cover zones have been developed (Stewart and Oke, 2009 a, b) that are useful for documenting metadata of urban monitoring sites and for characterizing surface features in urban modeling tools.


FIGURE 3.2 Variability of land cover zones in New York City characterized by: differences in surface morphology, percentage of surface cover, and sources of heat, water, other gases, and particulates. SOURCE: Sue Grimmond and Bing Maps.



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