Exploring atmospheric evaporative demand in relation to wildland fire

Abstract

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 western 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 as well as inputs to other fire danger systems. Thus, correspondence between evaporative demand and fire danger can be expected and this has previously been demonstrated such as via the Evaporative Demand Drought Index (EDDI) indicator. For example, EDDI can be decomposed to examine the weighted physical factors over time leading up to a fire event. Utilizing evaporative demand for monitoring and prediction can serve as an early warning of significant fire potential weeks to possibly months in advance. Similarly, evaporative demand can 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 with an ultimate goal to better understand if and how evaporative demand can be used to inform wildland fire management decisions.