Integrating Satellite Observations for Large-Scale Characterization and Monitoring of Flash Droughts in the Contiguous United States

Abstract

Flash droughts are characterized by rapid onset and intensification, capable of significantly impacting agriculture and ecosystems. Flash drought typically starts as a meteorological drought, which can progress into an agricultural drought if conditions worsen. This type of drought is primarily marked by extremely high air temperatures and soil moisture deficits. While the primary cause of drought is a lack of precipitation, other atmospheric and hydrologic anomalies can accelerate the development and severity of flash droughts. For example, low precipitation conditions, combined with high evaporative demand due to elevated air temperatures, low relative humidity, and clear skies, can lead to the rapid emergence of agricultural drought conditions, primarily manifested as increasing soil moisture deficit. As a result, multiple factors can contribute to the occurrence of flash droughts, and it is important to utilize a wide range of reliable data sources to monitor the emergence and expansion of flash droughts. While prior studies have generally examined flash drought evolution using reanalysis data, there has been no comprehensive exploration of flash drought development at large scales, incorporating a wide range satellite observations. In this study, we characterized flash droughts over the continental US using remote sensing data between 2003 and 2020. Here we employ a unique combination of satellite climatic, agricultural, and ecological variables to investigate large-scale flash drought development. These variables include Atmospheric Infrared Sounder (AIRS) Vapor Pressure Deficit (VPD), Relative Humidity (RH), Temperature (T), GLDAS Soil Moisture, Global Precipitation Measurement (GPM) Precipitation, Moderate Resolution Imaging Spectroradiometer (MODIS) Evapotranspiration, MODIS Leaf Area Index (LAI), and Orbiting Carbon Observatory-2 (OCO-2) Contiguous Solar-Induced Chlorophyll Fluorescence (CSIF). Flash drought events are defined based on soil moisture, with all variables aggregated into 8-day (octad) averages for analyzing their temporal evolution and lead-lag correlations against soil moisture. Finally, the deteriorating impact of flash droughts associated with background aridity should be considered while monitoring their agricultural, and ecological impacts. Here we also investigate ecosystem responses to flash droughts in 5 different regions characterized utilizing the Aridity Index (AI) across the Contiguous United States (CONUS).