A wide range of complex urban processes and their interactions with large-scale atmospheric processes define the heterogeneity of urban microclimates, with major implications for communities living in them. These dynamics are unique to each city and influenced by urban morphology (e.g., building height, road width, building density, etc), the heat emitted by buildings and transportation, built materials, urban vegetation, and irrigation patterns. Understanding the interplay between these fine-scale processes and large-scale climate processes is necessary to predict the implications of climate change for extreme heat risk and energy demand in urban areas and to inform adaptation efforts. 

We have developed a state-of-the-science urban climate modeling capability, centered around WRF-UCM-EnergyPlus, with a focus on capturing the heterogeneity of urban microclimate dynamics under extreme conditions at the neighborhood level. This modeling framework uses a sophisticated multi-layer urban canopy model and incorporates detailed representations of urban morphology, building processes, urban vegetation, and irrigation. We employ an innovative approach to prescribing urban surface characteristics and processes that decouples them from land use/land cover classifications, allowing us to separate the impacts of each driving process on urban climate dynamics. For instance, we directly incorporate EnergyPlus-simulated heat emissions from buildings, heat emissions from transportation, IM3’s NATURF-based urban morphology, and remote sensing-based high-resolution (~3 m) maps of urban vegetation (type and fraction) and irrigation patterns. 

Using this modeling capability, we investigate how historic urbanization resulted in highly variable heat profiles under extreme heat conditions across neighborhoods in Los Angeles. We highlight the significant impacts of anthropogenic heat emitted by the buildings on the ambient temperatures and the feedback between building HVAC heat rejection and outdoor temperatures. Using the thermodynamic global warming (TGW) approach, we investigate the impact of climate change on urban climate dynamics, particularly under extreme heat conditions. Using our new understanding of the main mechanisms contributing to urban heat island effects and projections of climate change and urbanization in Los Angeles, we identify adaptation pathways, tailored to each neighborhood, that have the most potential for offsetting the urban heat island effects and climate change