The Soil Moisture Active Passive (SMAP) “Root Zone Soil Moisture Uncertainty (L4,12z Instantaneous, Model Value-Added)” layer displays uncertainty estimates of model-derived global root zone soil moisture of the top 100 cm of the soil column in m³/m³ posted on a 9 km EASE-Grid 2.0. Root zone estimates are obtained by merging SMAP observations with estimates from a land surface model in a soil moisture ensemble data assimilation system. Error estimates are derived from the ensemble standard deviation of the analyzed fields. 12z (or 12:00:00 UTC) indicates the time of the analysis update.

The SMAP spacecraft carries two instruments, a radar (active) and a radiometer (passive), that together make global measurements of land surface soil moisture and freeze/thaw state. It is useful for monitoring and predicting natural hazards such as floods and droughts, understanding the linkages between Earth’s water, energy and carbon cycles, and reducing uncertainties in predicting weather and climate.

References: SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update

Data field: sm_rootzone_analysis_ensstd