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With the rise of global temperature, many cities are suffering from more and more frequent extreme heat in hot summers. Quantitative information on the spatial distributions of urban heat has become more and more important for extreme heat mitigation and adaptation in cities. This study first investigated the fine-level heat hazard distributions at the sidewalk and building block level from the pedestrian perspective in Philadelphia, Pennsylvania. The urban microclimate modeling based on a high-resolution urban geometrical model was used to generate the 1m resolution outdoor heat hazard map in the study area. The sidewalk map was overlaid on the generated high-resolution heat hazard map to estimate the sidewalk level heat hazard. Based on the sidewalk level heat hazard map, this study further calculated the heat hazard level in the 400m walkshed along sidewalks for each building block. The building level hazard data were then aggregated at the census tract level to compare with the socioeconomic and racial/ethnic variables. The result shows that neighborhoods with higher proportion of African Americans have a higher heat hazard level in Philadelphia. This study would provide new insights for developing more thermally comfortable and pedestrian-friendly neighborhoods in the context of climate change.
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This content will become publicly available on December 1, 2026
Compound atmospheric drivers of the catastrophic 2025 Los Angeles urban firestorm
Abstract Urban firestorms are a growing hazard in fire-prone regions worldwide due to increasingly dry vegetation and expanding populations at the wildland-urban interface. In January 2025, the city of Los Angeles, California (USA), experienced an unprecedented fire disaster that destroyed over 16,000 structures and caused 31 fatalities. The event was driven by a rare “jet-forced Santa Ana” wind subtype featuring an amplified upper-level ridge over the West Coast and retrograding trough over the central/eastern U.S., producing extreme northerly flow, large-scale subsidence, and mountain wave activity that impeded aerial fire suppression. While the extreme surface winds were not unprecedented, their occurrence ahead of the first winter rain was uncommon. Despite accurate multi-day forecasts, response systems were overwhelmed. Our analysis shows how upper-level atmospheric support can drive surface fire weather, compounding hazard in even well-developed areas. This underscores the importance of aligning long-range prediction with operational preparedness and communication strategies in California’s variable hydroclimate.
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- Award ID(s):
- 2209058
- PAR ID:
- 10707718
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- npj Natural Hazards
- Volume:
- 2
- Issue:
- 1
- ISSN:
- 2948-2100
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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