One of the immediate expressions of climate change is the increased frequency and intensity of extreme heat events. In urban areas, extreme heat interacts with the heterogeneity of built surfaces and processes that can exacerbate or counteract their effects. Understanding which factors - built surfaces, building energy use, vegetation, etc. - contribute most to urban heat in different locations and time periods can help to identify strategies for urban heat mitigation.

In this study, we combine high-fidelity urban microclimate modeling with remotely sensed and ground-based observations to better understand how mesoscale processes interact with complex topography, urban morphology, building energy systems, and vegetation cover to shape neighborhood-scale variability in thermal environments during extreme heat events. We use WRF (Weather Research and Forecasting Model), coupled to a single-layer Urban Canopy Model (UCM), a series of building energy models (EnergyPlus), and an urban irrigation scheme to resolve urban microclimate dynamics and represent detailed urban processes such as anthropogenic heating from buildings and urban irrigation. High-resolution real-time remote sensing data is further incorporated into the modeling framework for an improved representation of urban surface physical characteristics such as albedo and green vegetation fraction.

We use the Los Angeles metropolitan area as a testbed where we employ the described modeling framework to reproduce neighborhood-scale micro-climate dynamics during a prolonged extreme heat condition in July 2018. We use an experiment design where one of the local anomalies that represent urban surfaces (i.e., buildings, roads, vegetated landscapes, anthropogenic heating, and irrigation) is successively added to a pre-settlement (no urban) scenario so as to quantify its effect. Our results decompose the contributing factors to the micro-climate thermal profiles and quantify the role of urban morphology, buildings, vegetated urban landscapes, anthropogenic heating, and urban irrigation on the heat profile of each neighborhood in the Los Angeles metropolitan area. By identifying the dominant contributing factors, we identify adaptation pathways that are tailored to each neighborhood to moderate the local extreme heat impacts.