Potential Utility of Atmospheric Evaporative Demand in Assessing Wildland Fire Potential

Evaporative demand, the upper limit of actual evapotranspiration (ET) that could occur given unlimited surface water supply, has a strong connection to drought and wildfire potential in the United States and globally. A physically based evaporative demand formulation incorporates temperature, wind speed, humidity, and incoming shortwave radiation – components that drive land surface‐atmosphere interactions and drying. These are also the primary physically based components in the U.S. National Fire Danger Rating System; various combinations of temperature, humidity, and wind speed are also common inputs to other fire danger systems. Thus, an association between evaporative demand and fire danger can be expected, which has previously been demonstrated via the Evaporative Demand Drought Index (EDDI). The EDDI varies by ecoregion across the contiguous United States even under non-drought conditions, with higher EDDI in the water-limited southwest and lower EDDI in the energy-limited northeast. Consequently, the EDDI anomaly necessary to increase fire danger also likely varies by ecoregion and fuel type. Additionally, EDDI can be decomposed to examine the weighted physical factors over time leading up to a fire event. Utilizing evaporative demandfor monitoring and prediction can serve as an early warning of fire potential depending on climatological persistence patterns for weeks to possibly months in advance though rapid onset anomalies may yield a similar result. Evaporative demand can also inform prescribed burn planning. Based on the exploration of EDDI indicators prior to fire events, this presentation will discuss analyses of evaporative demand in the context of both wildfire and prescribed fire to better understand if and how evaporative demand can be used to inform wildland fire management decisions.