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ensure accuracy. Understanding the Changing Planet: Strategic
Directions for the Geographical Sciences FIGURE 4.3 Annual
precipitation anomalies, 1900–1988. Regions in blue show an
increase in precipitation over the mean during the 1900–1988
period. Regions in red have become relatively drier during the
same period. Areas without data are shown in white. SOURCE: Dai
et al. (1997). that urban land uses and urban expansion through
land-cover change can affect local, regional, and global climate
at diurnal, seasonal, and long-term scales (Stohlgren et al.,
1998; Zhou et al., 2004). A clearer picture is emerging that
urban areas can affect climate at different scales. However, we
lack a comprehensive understanding of the dynamics by which
urban expansion will affect climate; nor do we understand the
interactions between local-scale d