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Top1. Introduction
Australia may face a likely 3.8°C increase in surface temperature by 2090 (the worst scenario: A1F1) (CSIRO, 2007). Such an increase in temperature will have a severe impact on regional and local climate systems, natural ecosystems, and human life in cities. Heat stress can reach up to 10°C in urban settings compared to their peri-urban surroundings (Erell et al., 2011). Natural landscapes in and around cities are increasingly replaced by hard and impermeable surfaces during urban development projects (Girardet, 2008, Harden et al., 2014). Shortage of vegetation cover in cities, alongside urban structure and hard surfaces, cause an artificial temperature increase in urban environments (Gartland, 2008, Stone, 2012). The artificial heat stress in cities has a particular threat for usability and health-safety of outdoor living in public space (Nikolopoulou, 2004, Kovats and Hajat, 2008). In response to such substantial extra heat load in cities, people increasingly move into air-conditioned buildings to benefit from the indoor thermal comfort. However, anthropogenic heat – generated from indoor air-conditioning – causes an ever-increasing outdoor temperature.
In this context, this paper aims to determine the daily patterns of urban warmth in Adelaide metropolitan area via a mobile traverse method. A better understanding of daily urban warmth variations in cities assists urban policy making and public life management in the context of climate change.
1.1. Background
Large-scale changes in the natural landscape cause urban space inhabitants to suffer from the effect of an artificial heat stress in cities relative to their peri-urban vicinities, known as the urban heat island (UHI) effect. Background literature of the UHI effect indicates that such artificial increase of urban temperature occurs because of changes in energy and water budget in the built environment (Karatasou et al., 2006a, Oke, 2006b, Gartland, 2008, Erell et al., 2011 (Soltani, Mehraein, & Sharifi, 2012)). Howard’s study of urban warmth in London indicates that the mean annual temperature (20-years average) in London central area is 2.5°C higher than its countryside (1833). The peak temperature difference of 3°C is reported during February (mid-winter). Similar urban heat stress has been reported in Paris by the second half of the 19th century (Gartland, 2008, Stewart, 2011).
The UHI investigations are commonly document the UHI phenomenon and its behaviour. These large-scale urban climate studies contribute mainly to the understanding of the UHI effect mechanism via comparing city centres and their rural surroundings (Oke, 1987, Oke, 1988, Paterson and Apelt, 1989, Tapper, 1990). Numerous case studies strongly support the relatively higher temperature in highly developed urban areas including city centres (see Figure 1). However, the accuracy and applicability of many of these case studies are under criticism in more advanced urban climate research by highlighting instrumental and measurement variations (Oke, 2006b, Stewart, 2011).
Figure 1. Reported magnitude of the UHI effect in 12 cities since the 1980s