Drought at Seen Through the Prism of Soil Moisture Observations

Soil moisture observations have been deemed to be important to climate monitoring in the U.S. for many years, but are often available only seasonally where measurements are taken for practical irrigation purposes in agricultural and horticultural settings. Sites with permanent soil moisture measurement are less common, but USDA and NOAA have deployed national climate observation networks with soil moisture measurement capabilities in stationary locations, and several states also have such arrays. However, many of these times series are rather brief, and only a small number have a sufficient climatology to statistically understand the distribution of soil moisture states versus observed drought conditions in various regions. In this presentation, soil moisture measurements taken mainly from longer term records will be related to various drought indices derived from temperature and precipitation data, especially examining lead/lag relationships. In the period since the 2000s, U.S. Drought Monitor (USDM) status will also be examined relative to observed soil moisture at various depths. Finally, a case study will be made of the 2012 drought in the central U.S. and its development in both drought indices and USDM status as compared to soil moisture. The USDA Soil Climate Analysis Network and the NOAA U.S. Climate Reference Network will be featured in the case study.