Analysis of patterns in remotely-sensed soil moisture and evapotranspiration throughout the days before the 2023 Maui wildfires

Wildfires can spread rapidly in dry areas affected by higher temperatures and lower precipitations. In some instances, such as for the recent wildfires in Maui, the dry conditions intensified in a short period of time on the order of a few weeks. This phenomenon known as "flash-drought" can severely impact certain components of the hydrological cycle, including evapotranspiration (ET) and soil moisture. A rapid increase in temperature can drive higher ET rates. And as water is transferred from the land to the atmosphere, soil moisture also decreases rapidly. These changes in the weather and their effects on the ground can be captured using Earth observations from space. The present study focused on the conditions preceding the series of wildfires that devastated the island of Maui in early August 2023. We leveraged measurements from the Soil Moisture Active Passive (SMAP) mission at various levels and resolutions. We also utilized ET data from the Terra Moderate Resolution Imaging Spectroradiometer. Next, we examined pre-fire conditions and the propagation of the drought in the days and months before the disaster. We analyzed the severity of anomalies in soil moisture and ET relative to available data records. We also compared spatial patterns and overlap across the various satellite products. Overall, this work will provide insights on the hydrological conditions that exacerbated fire susceptibility, with the aim to augment future wildfire risk assessment and management efforts.