Abstract
Surface urban heat islands (SUHIs) are influenced by the spatial distribution of green space, which in turn can be influenced by urban planning. When studying the relationship between structure and function it is critical that the scale of observation reflects the scale of the phenomenon being measured. To investigate the relationship between green space pattern and the SUHI in the Kansas City metropolitan area, we conducted a multi-resolution wavelet analysis of land surface temperature (LST) to determine the dominant length scales of LST production. We used these scales as extents for calculating landscape metrics on a high-resolution land cover map. We built regression models to investigate whether–controlling for the percent vegetated area–patch size, fragmentation, shape, complexity, and/or proximity can mitigate SUHIs. We found that while some of the relationships between landscape metrics and LST are significant, their explanatory power would be of little use in planning for green infrastructure. We also found that the relationships often reported between landscape metrics and LST are artifacts of the relationship between the percent of vegetation and LST. By using the dominant length scales of LST we provide a methodology for robust biophysically-based analysis of urban landscape pattern and demonstrate that the contributions of green space configuration to the SUHI are negligible. The simple result that increasing green space can lower LST regardless of configuration allows the prioritization of resources towards benefiting neighborhoods most vulnerable to the negative impacts of urban heat.
Highlights
Urban areas occupy only a small fraction of the earth’s surface, they are home to more than half of the world’s population, a figure that is expected to increase to more than two-thirds by 2050 [1]
A widely recognized characteristic of urban areas is an increase in temperature relative to surrounding rural areas known as the urban heat island (UHI) effect, a consequence of anthropogenic heat, decreased albedo, increased thermal capacity, and decreased evapotranspiration [5,6]
These studies have analyzed pattern within extents that are not defined by the biophysical interactions that produce land surface temperature (LST) [17,22,24,27,28,29,31]
Summary
Urban areas occupy only a small fraction of the earth’s surface, they are home to more than half of the world’s population, a figure that is expected to increase to more than two-thirds by 2050 [1]. A widely recognized characteristic of urban areas is an increase in temperature relative to surrounding rural areas known as the urban heat island (UHI) effect, a consequence of anthropogenic heat, decreased albedo, increased thermal capacity, and decreased evapotranspiration [5,6]. The surface UHI (SUHI) is defined for the urban land surface, and is measured by remote sensing instruments as upwelling thermal radiance [3]. The spatial distribution of SUHIs is a manifestation of the surface energy balance and is strongly dependent on the presence or absence of vegetation [6,8,10], with vegetated areas being potentially 2–8 ◦C cooler than surrounding areas [9]
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