Exploring the Impacts of Reduced Snowpack Due to Light Absorbing Aerosols in Snow, Including Potential Influence on Wildfires

The mountain snowpack is an essential resource for both the environment as well as society. Recent studies have shown light-absorbing aerosols (LAA) in snow such as desert dust and black carbon to be important players in surface energy and water budgets of mountain areas across Western United States (WUS). The presence of LAA in snow, by shifting snowmelt timing, can have an impact on soil and vegetation conditions in subsequent months. Based on historical data, strong correlations were found between snowmelt timing and wildfire activity, with the suggestion that a shorter snow season can lead to drier soil and vegetation conditions, which implies greater opportunities for wildfires. In this study, we aim to investigate the impact of a reduced snowpack and earlier snowmelt due to LAA in snow on wildfire risk across various regions of WUS, including the Cascade, Sierra Nevada, and southern Rocky Mountains.  To achieve this goal, we employ a regional climate model with a physically-based snow scheme that accounts for presence of LAA in snow. By comparing the LAA-loaded and LAA-free simulations over 10 years, we explore the changes induced by LAA to the water balance, as well as potential implications to wildfires. (KEYWORDS: dust and black carbon in snow, runoff changes, regional climate modeling, western United States, hydrologic cycle, wildfire risk)