Evaluation of the SMAP Level 4 Surface and Root-Zone Soil Moisture Product

Abstract:

The SMAP Level 4 soil moisture product (L4_SM) provides global estimates of surface and root-zone soil moisture, along with other land surface variables and their error estimates. These estimates are obtained through assimilation of SMAP brightness temperature observations into the Goddard Earth Observing System (GEOS-5) land surface model. The L4_SM product assimilates tens of thousands SMAP observations daily, is provided at a 9 km spatial resolution and 3-hourly spatial resolution and with a 2-3 day latency. This presentation will provide an overview of the L4_SM product and algorithm.

The soil moisture and temperature estimates in the SMAP L4_SM product are evaluated against in situ observations collected within coarse-scale core validation sites and against point-scale measurements obtained from sparse networks. An early evaluation shows that the SMAP L4_SM product meets the set target uncertainty of 0.04 m³/m³, measured in terms of unbiased root-mean-square-error, for both surface and root-zone soil moisture.