May 22 - July 30
Improving Wildfire Risk Assessment in the Continiguous U.S. (1981-2020) Using a High-Resolution Regional Climate Model
Miranda Bognar, Xiaodong Chen, Wenjun Cui
What is already known:
- Wildfires pose a serious and growing threat to communities and ecosystems.
- Current fire weather risk assessments utilize coarse-resolution global climate data.
- Peak wildfire potential occurs during the months of May through October.
What this study adds:
- High-resolution fire weather risk assessments using the CONUS404 climate model output.
- Evidence for increasing fire weather risk across the contiguous United States over the past four decades.
- Increasing wildfire potential in the early and late months of the year, suggesting an extension of the traditional fire season.
- Strong correlation between long-term changes in precipitation and fire weather risk.
Abstract:
Wildfires have historically played an important ecological role, promoting biodiversity through natural landscape renewal. However, in recent decades, wildfire activity has become increasingly destructive, posing significant threats to ecosystems, infrastructure, and communities. This study investigates changes in fire weather conditions, as measured by the Fire Weather Index (FWI), across the contiguous United States from 1981–2020, focusing on regional and seasonal trends. Unlike traditional fire risk assessments that rely on coarse-resolution atmospheric reanalysis and global climate models, this study utilizes CONUS404, a convection-allowing regional climate model output. With its 4 km spatial resolution, COUNS404 is better at capturing localized fire weather conditions over complex terrains than these traditional datasets. Analysis across the four U.S. subregions (Pacific, Mountain, Central, Eastern) reveals the large-scale spatial variabilities of wildfire risk. In particular, the Pacific zone exhibits the highest and most rapidly increasing annual average FWI, indicating greater vulnerability to wildfire. Seasonal increases in average monthly FWI were observed during the early and late months of the year, particularly in January and November, suggesting a potential extension of the traditional fire season into winter and spring. Compared to the FWI derived from ERA5 (at 25 km resolution), CONUS404-based FWI captures more local-scale spatial heterogeneity of wildfire risks at finer scale, especially in topographically complex regions such as the western US. These findings highlight the need for high-resolution climate data in future wildfire research and risk management, particularly as fire seasons grow longer and more intense.