Fig. 4: Temperature data monitored across the Chicago Loop.

a Average monthly temperature trend, \(\bar{T}\), over time, \(t\) (\({\bar{T}}_{{{{{\rm{sur}}}}}}\): monthly average surface air temperature monitored by the developed sensing network and NOAA⁵⁷; \({\bar{T}}_{\max }\) and \({\bar{T}}_{\min }\): maximum and minimum values of monthly average surface air temperature monitored by NOAA⁵⁷; \({\bar{T}}_{{{{{\rm{water}}}}}}\): monthly average water temperature monitored by NOAA⁵⁷; \({T}_{{{{{\rm{grass}}}}}}\) and \({T}_{{{{{\rm{streets}}}}}}\): grass and street temperature values determined through the analytical expression proposed by Baggs⁵⁹ and the coefficients reported by Jense-Page et al.⁶⁰, where \({T}_{0,g}\) is the initial undisturbed ground temperature, \({t}_{o}\) is the time in days until the time the minimum air temperature from January 1^st is measured for any considered location, \({A}_{s}\) is the amplitude of the annual temperature variation measured for any considered location, and \({\alpha }_{d,g}\) is the ground thermal diffusivity); b Relationship between surface air temperature, \({T}_{{{{{\rm{sur}}}}}}\), and subsurface air temperature, \({T}_{{{{{\rm{sub}}}}}}\), for different underground built environments across the Loop (\({R}^{2}\): coefficient of determination). The 3-D view of the sensing network has been created with a baseline image provided by OpenStreetMap.