A Posterior Designed Soil Moisture Network for the Validation of SMAP Products.

The 2011 drought in Texas resulted in a total water storage deficit of over 60 km³ with soil moisture accounting for 20-100% of this loss. Following the successful launch of NASA’s Soil Moisture Active Passive (SMAP) satellite, we have now received over 18 months of globally mapped soil moisture at unprecedented accuracy and resolution. Using a combined passive L-band radiometer and active L-band radar, soil moisture to 5 cm depth is retrieved at 3, 9 and 36km spatial resolutions every few days. The primary SMAP mission objectives is a soil moisture product with an unbiased error <0.04 m³ m^-3 to ground-based networks. However, few such monitoring networks exist at the scale appropriate to validate SMAP, or any other LSM or remote sensing product. In response to this need, we built the Texas Soil Moisture Observation Network (TxSON): an intensively monitored watershed (1300 km²) located on the Edwards Plateau along the Pedernales River. TxSON consists of over 40 monitoring stations nested within the Equal-Area Scalable Earth Grid with replicated soil moisture sensors installed at 5, 10, 20 and 50 cm depths. This presentation will highlight our validation efforts towards the SMAP mission and the on-ground activities related to large-scale soil moisture validation and its importance to rangeland productivity, groundwater recharge and flooding across Texas.