Alys Thomas

We supplement present-day hydrological drought characterization with a new quantitative framework for measuring the severity of regional water storage deficits based on terrestrial water storage observations from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellite mission. GRACE measurements are applied for hydrological drought characterization by calculating the deviation of monthly, terrestrial water storage anomalies (TWSA) from a 127-month climatology, where negative deviations represent storage deficits. Each monthly deficit explicitly quantifies the volume of water required to return to normal water storage conditions. We use the ‘storage-deficit’ method to quantify the severity of continuous periods of water storage deficits by combining average storage deficits with event duration. Two drought databases are referenced to identify specific meteorological drought events that occurred during the 2002-present GRACE mission lifetime in the Amazon and Zambezi River basins and in the southeastern United States and Texas regions. The storage deficit method quantifies the instantaneous and peak magnitude of water storage deficits, demonstrating the added benefits of explicitly recognizing the beginning and end of storage deficit periods and of providing additional information about the effects of meteorological drought on regional water storage.