Assessing flash drought development and propagation across the contiguous United States using remote sensing

Flash droughts are characterized by rapid onset and intensification, with severe impacts on agriculture and ecosystems. They often begin as meteorological droughts and, if conditions worsen, evolve into agricultural droughts. While precipitation deficit is often the primary driver, atmospheric and hydrological anomalies can exacerbate flash drought development. This study characterizes flash droughts across the Contiguous United States using remote sensing data from 2003 to 2020. A combination of satellite-derived meteorological, agricultural, and ecological variables are used to investigate large-scale flash drought development. Events are defined based on root zone soil moisture, with the Aridity Index included to assess how background aridity influences agricultural and ecological impacts. Cross-correlation and Cross Wavelet analyses are applied to examine the propagation of flash droughts from meteorological to agricultural and ecological stages. Results show that flash drought characteristics - including frequency, duration, and onset/recovery rates - are significantly influenced by landscape aridity characteristics. Precipitation is identified as the main driver across all climate regimes while Relative Humidity (RH) and Vapor Pressure Deficit (VPD) also indicate early signals. Time lags between meteorological variables and Soil Moisture (SM), as well as between soil moisture and ecological variables, vary across climates. Generally, results show that ecosystems respond to flash drought after soil moisture. Solar Induced Fluorescence (SIF), a measure of ecological stress, detects flash drought onset earlier than SM, highlighting its potential for early detection and monitoring.