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A. Colliander, T. Jackson, S. Chan, N. Das, S. Kim, M. Cosh, R. Dunbar, J. Asanuma, K. Aida, A. Berg, T. Rowlandson, D. Bosch, T. Caldwell, K. Caylor, C. Holifield Collins, H. al Jassar, E. Lopez-Baeza, J. Martínez-Fernández, Á. González-Zamora, S. Livingston, H. McNairn, A. Pacheco, M. Moghaddam, C. Montzka, C. Notarnicola, G. Niedrist, T. Pellarin, J. Prueger, J. Pulliainen, K. Rautiainen, J. Ramos, M. Seyfried, P. Starks, Z. Su, Y. Zeng, R. van der Velde, M. Thibeault, W. Dorigo, M. Vreugdenhil, J. Walker, X. Wu, P. OŽNeill, D. Entekhabi, S. Yueh:
"Soil Moisture Validation Using In Situ Measurements: The Smap Approach";
Talk: 37th International Symposium on Remote Sensing of Environment 2017 (IRSE 37), Tshwane, South Africa; 2017-05-08 - 2017-05-12.

NASAŽs Soil Moisture Active Passive (SMAP) Mission was launched in January 2015. The objective of the mission is global mapping of soil moisture and landscape freeze/thaw state. The primary validation reference of the data products are ground-based measurements. Well characterized sites with multiple calibrated in situ sensors within the SMAP 40-km footprint have been used to determine the quality of the data products; these sites are designated as core validation sites. The mission success has been evaluated with respect to these core site comparisons. Sparse networks of soil moisture stations and other remote sensing and model-based products have been used as complimentary resources to expand the spatial and temporal scope of the evaluation.
In an effort to ensure the geographic distribution and diversity of conditions captured by the core validation sites, SMAP partnered with investigators across the globe. Because different SMAP Level 2 and 3 soil moisture products have different spatial scales, the suitability of the various sites for validation of the different products was assessed considering several factors. The main factors were the availability of a geographically distributed in-situ soil moisture network consisting of multiple points, gravimetric calibration of the in situ sensors within a site, determination of a spatial scaling function of the sensor measurements up to the SMAP resolution scales, and timely accessibility of the data.
The mission has been able to utilize the core site measurements since the launch of the satellite because the infrastructure for data transmission and processing was established well before the launch. The validated SMAP soil moisture products were released in May 2016. This presentation will show the performance of the latest radiometer-based surface soil moisture data products using 2 years of data, and discuss the lessons learned during the validation process.