Urban impacts on climate - The Global Climate System: Patterns, Processes, and Teleconnections - page 217

The first major urban climate experiment, the METROpolitan Meteorological
EXperiment (METROMEX), occurred in St Louis (USA) in the early 1970s.
Interest and the literature in urban climates were expanding rapidly. In 1972,
P. Rao introduced the use of remote sensing from satellites for urban heat island
analysis. In that year, the American Meteorological Society held its first con-
ference on the urban environment. In 1974 and 1975, the first detailed work on
urban canyons began. Further reviews on urban climate during the 1970s were
produced by T. Oke for the WMO. In 1981, Helmut Landsberg's landmark book,
The Urban Climate, was published by Academic Press, followed in 1985 by The
Urban Atmosphere by B. Atkinson.
Since then there have been major improvements to urban climate research and
understanding. This chapter explores our current understanding of the impacts of
urban areas on climate, most of which are broadly summarized in Table 7.2 .
Following literature trends, it provides a major focus on the urban heat island
(UHI). A description of the energy balance, urban heat island development, and
aspects of methodology occurs in an essay by Sue Grimmond. Sections on wind,
urban canyons, moisture and precipitation, air pollution, and remote sensing
follow. Examples from specific cities are used in support of the discussion,
especially Melbourne, Australia, Mexico City, and G¨ teborg, Sweden (see
Background Box 7.1 ). The chapter ends with some comments about ways to
mitigate urban impacts on climate.
Background Box 7.1
Cities used as major urban examples
Melbourne, Australia
Melbourne has a population of about 3.6 million people, and is located in southern
Victoria, Australia, at the head of Port Phillip Bay (37849 0 S, 144838 0 E). Melbourne
is under the influence of the mid-latitude westerlies in winter and subtropical
circulation in the summer. The city is surrounded on three sides by higher elevations,
but these are not consistent in altitude and there are gaps. To the south, the Bay exerts
some influence on the regional climate, but not enough to overcome the influence of the
city itself.
Mexico City, Mexico
Mexico City is located in a mountain environment at 10825 0 N, 99810 0 W. It is
considered to be a tropical city, but is located at an altitude of 2250 m. In a valley,
surrounded by mountains, and under the synoptic control of the semi-permanent
subtropical high in the eastern North Pacific, Mexico City provides the classic
environment for major air pollution episodes and urban climate impacts. With a
population of about 20 million people, and major emissions from traffic and industry,
Mexico City is rated by UNEP as one of the three most polluted cities in the world