Seasonality of the Urban Heat Island Effect in Madison, Wisconsin

Abstract

Spatial and temporal variation in the urban heat island (UHI) effect from March 2012 through October 2013 was characterized using continuous temperature measurements from an array of up to 151 fixed sensors in and around Madison, Wisconsin, an urban area of population 407 000 surrounded by lakes and a rural landscape of agriculture, forests, wetlands, and grasslands. Spatially, the density of the built environment was the primary driver of temperature patterns, with local modifying effects of lake proximity and topographic relief. Temporally, wind speed, cloud cover, relative humidity, soil moisture, and snow all influenced UHI intensity, although the magnitude and significance of their effects varied by season and time of day. Seasonally, UHI intensities tended to be higher during the warmer summer months and lower during the colder months. Seasonal trends in monthly average wind speed and cloud cover tracked annual trends in UHI intensity, with clearer, calmer conditions that are conducive to the stronger UHIs being more common during the summer. However, clear, calm summer nights still had higher UHI intensities than clear, calm winter nights, indicating that some background factor, such as vegetation, shifted baseline UHI intensities throughout the year. The authors propose that regional vegetation and snow-cover conditions set seasonal baselines for UHI intensity and that factors like wind and clouds modified daily UHI intensity around that baseline.

Evaluating the Role of Snow Cover in Urban Canopy Layer on the Urban Heat Island in Sapporo, Japan with a Regional Climate Model

“…These experimental results show that road snow clearing has a stronger effect on T min than on T max (not shown), which is consistent with the results of Schatz and Kucharik (2014). This result also indicates that the decrease in T max is attributable mainly to snow cover on roofs.…”

“…Therefore, snow cover in urban areas is of comparable importance to anthropogenic heat release when simulating the spatial air temperature contrast between urban and surrounding areas. Schatz and Kucharik (2014) reported snow depth effects on nocturnal surface air temperature through ground heat transfer change. To confirm the effect of snow depth and road snow clearing on urban surface air temperature, we conducted sensitivity experiments as the CL0, CL20, and NO_CL runs (Table 1).…”

“…Relationships between snow and urban heat islands have been explored in previous studies (Malevich and Klink 2011;Schatz and Kucharik 2014), and the following key results have been reported. 1) The effect of snow is smaller in rural areas than in urban areas because of dirty snow and relatively large snowfree areas such as walls and bare areas formed by snow melt in urban areas.…”

Spatio-Temporal Modeling of the Urban Heat Island in the Phoenix Metropolitan Area: Land Use Change Implications

“…The effect of the built-up environment manifests itself by impacting turbulent transport radiative heat exchange and hydrological processes, especially in urban canopies [36]. Schatz and Kucharik also demonstrated in their paper that the built-up environment was the primary driver of the spatial change in temperature patterns in the urban area [37]. They found that urban environments, together with their dark impervious surfaces and reduced vegetation cover, normally have large heat capacity and high thermal conductivity rates [34,[38][39][40][41][42].…”

The coastal convective interactions experiment

“…For coastal environments, the enhanced UHI thermal gradient has been associated with the earlier onset of the sea breeze, followed by stagnation over the urban environment as the sea breeze is perturbed by the UHI circulation (Melas et al 2000;Khan and Simpson 2001;Lemonsu et al 2006b;Freitas et al 2007). Furthermore, enhanced convergence, vertical motion and aerosols concentrations from the UHI has been documented in association with increased cloud formation (Tsunematsu and Kai 2004;Schatz and Kucharik 2014), convective precipitation rates (Dixon and Mote 2003;Ryu et al 2015) and storm initiation (Rozoff et al 2003;Shem and Shepherd 2009). Continuing growth of the near-coastal urban landscape (Small and Nicolls 2003) highlights that UHI processes are increasingly a significant component of the coastal PBL.…”