Microclimatic Variations Attributable to Urban-Canyon Asymmetry and Orientation

The energetic response of urban canyons to variable urban geometry is investigated using the URBAN3 numerical model. The energy budgets of six typical urban geometry scenarios encompassing a combination of symmetrical and asymmetrical north-south and east-west aligned urban canyons are examined for a warm summer day under which maximum inter-urban system energetic variations would be expected. Significant inter-urban canyon energy total differences are found which are closely linked to patterns of net solar radiation. The net solar radiation, net radiation and turbulent sensible heat flux totals are particularly sensitive to urban geometry. Implications of the study with respect to the magnitude of synoptic vs. geometric sources of urban energetic variation, and microscale and mesoscale urban modelling applications are discussed. [Key words: urban climatology, urban canyon energy budgets, urban geometry.]