The impact of vertical measurement depth on the information content of soil moisture times series data

Using a decade of ground‐based soil moisture observations acquired from the United States Department of Agriculture's Soil Climate Analysis Network (SCAN), we calculate the mutual information (MI) content between multiple soil moisture variables and near‐future vegetation condition to examine the existence of emergent drought information in vertically integrated (surface to 60 cm) soil moisture observations ( θ 0–60 [cm] ) not present in either superficial soil moisture observations ( θ 5 [cm] ) or a simple low‐pass transformation of θ 5 . Results suggest that while θ 0–60 is indeed more valuable than θ 5 for predicting near‐future vegetation anomalies, the enhanced information content in θ 0–60 soil moisture can be effectively duplicated by the low‐pass transformation of θ 5 . This implies that, for drought monitoring applications, the shallow vertical penetration depth of microwave‐based θ 5 retrievals does not represent as large a practical limitation as commonly perceived.