Satellite Base Soil Moisture Product Validation Using Ground Observations

Soil moisture is defined as the water contained in the spaces between soil particles. Soil moisture content is among most important physical parameters in hydrology, climate, and environmental studies. The Advanced Microwave Scanning Radiometer 2 (AMSR2) is one of many remotely sensors that collects daily information of soil moisture of the surface land. However, many factors such as ancillary data and vegetation scattering can affect the signal and the estimation. Therefore, this information needs to be validated against some “ground-truth” observations. NOAA – Cooperative Remote Sensing and Technology (CREST) center at the City University of New York has a site located at Millbrook, NY with several in situ soil moisture probes. In situ observations are conducted using soil moisture sensors (Stevens Digital Hydra Probe II) and Cosmic-Ray Soil Moisture Observing System (COSMOS probes). Soil moisture information was measured in seven different locations from 2012 to 2015. Hydra proves are used to measure six of these locations, which are located at Millbrook, NY and a COSMOS probe, for the last location, is located near the Savannah River, SC. Due to missing days and nigh, the total sample compared between satellite and ground measurements was reduced to less than 650 for both, days and nights. Analysis of the sensors and AMSR2 indicated a weak correlation with the hydra probes (less than 0.16) and a moderate correlation with COSMOS (between 0.25 to 0.42). Furthermore, root mean square error (RMSE) is used to measure the error indicating better results for COSMOS against Hydra probes. Finally, these results shows that the retrieval algorithm of AMSR2 is appropriate under certain circumstances and this validation can be used to provide information so that the algorithm can be improved over the area of the United States for future studies.