Understanding the Key Drivers of Anthropogenic Heat Impacts on Urban Temperatures
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Cities are increasingly warming due to anthropogenic heat from vehicles, industry, and homes, exacerbating discomfort and danger during heatwaves. Research demonstrates that urban air temperature sensitivity to anthropogenic heat is higher in winter than in the summer across the contiguous United States (CONUS). This effect is due to a weakened negative feedback from conductance leading to a higher urban air sensitivity to anthropogenic heat.
Scientists have discovered that anthropogenic heat from buildings, cars, and factories significantly affects urban temperatures. This study stands out by employing a novel method to assess how various factors influence city heat dynamics. Crucially, it reveals how heat transfer between city air and the atmosphere is key to predicting urban temperatures, aiding in cooler city designs. The research also examines the sensitivity of city temperatures to human-made heat across seasons and times, informing urban planning and policy-making. This knowledge is vital for creating energy-efficient cities and keeping urban heat in check.
Recent research introduces a new framework to examine the response of urban canopy air temperature (Ta) to anthropogenic heat flux (QAH), focusing on the sensitivity (∆Ta/∆QAH) across urban areas in the contiguous United States. Utilizing the Community Land Model Urban, findings indicate a median summer sensitivity of 0.01 K(W m−2)−1, with feedback from surface temperature changes and heat conductance between the canopy air and atmosphere largely offsetting each other. Winter sensitivity increases by about 20% due to reduced negative feedback from atmosphere-canopy air heat conductance (ca).
The study highlights significant spatial and temporal variability in ∆Ta/∆QAH, with a strong link to ca variability, underscoring the need for precise convective heat transfer parameterization in urban canopy models. It reveals that Ta sensitivity to QAH is influenced not just by QAH magnitude but also by urban canopy feedback processes, particularly convective heat transfer. The findings stress the importance of atmosphere-canopy air heat conductance in urban thermal regulation and suggest that enhancing this aspect in urban climate models is crucial for accurate predictions.