An investigation of soil moisture extremes over the 2012 drought

Soil conditions are an integral component of both climate and weather variability. This is particularly true for soil moisture where the soil column acts as evapotranspiration reservoir to the atmosphere, impacting regional and local energy and water cycles. These soil-atmosphere interactions can result in important feedbacks particularly in extreme hydrological events such as droughts, resulting in warmer surface temperatures. However, investigations of soil-atmosphere interactions are often limited by the scarcity of available in-situ soil measurements in addition to the lack of a long data record, selection of soil monitoring instrumentation, and installation techniques. In this study we explore the use of a cumulative distribution function (CDF) as a tool to identify in-situ soil moisture extremes from short-term station records. The CDF metric ranks soil moisture measurements by percentile based on observations from a base period. The CDF values for a station can range from 0 (driest) to one (wettest), and may be more useful in a spatial context than traditional volumetric measurements that can range substantially by soil profile. The U.S. Climate Reference Network (USCRN), which monitors soil conditions in near-real time from 113 locations across the contiguous U.S. since 2011, provide an opportunity to analyze soil moisture extremes over the 2012 drought. The use of station based CDFs may prove to be a useful monitoring product for sub-surface drought conditions across the U.S.