New Insight into the Development of Flash Drought: A Case Study at the Marena Oklahoma In Situ Sensor Testbed

Flash droughts are extreme, short-term events distinguished by a lack of precipitation, soil moisture deficits, and anomalously high surface temperatures. During the summer of 2012, flash drought occurred across many locations in the Southern Great Plains of the United States. This study utilized the over 200 soil, vegetation, and atmospheric sensors installed at the Marena Oklahoma in Situ Soil Moisture Testbed (MOISST) to investigate the role played by land-atmosphere interactions in the development of flash drought. In particular, the role of vegetation was examined as related to the ecosystem collapse in the region. Results from the analysis demonstrated that as atmospheric demand increased in July 2012, the vegetation rapidly depleted the available water in the soil profile. Without additional rainfall to replenish the soil column, the vegetation quickly reached the wilting point and failed. The reduced soil moisture and active vegetation yielded evapotranspiration that significantly decreased from a peak greater than 10 mm per day in late June to less than 2 mm per day in mid August. As a result, surface temperature values increased and perpetuated the local drought conditions. In the end, the complex interactions between the soil, the vegetation, and the atmosphere led to the rapid transition from abnormally dry conditions on 1 July 2012 to exceptional drought on 15 August 2012 – a period of just 6 weeks.