The validation of the final merged data set is an important mechanism within the production process of the ECV SM products. The validation is conducted by project partners who are independent from the development of the ECV SM data set. Results of the validation and intercomparison studies for each of the released versions of the product are described in detail in the corresponding Product Validation and Intercomparison Report (PVIR).
Correlation of the gridded soil moisture products as compared to in-situ station observations for the full year for the US. Subdivided in consecutive 4-year periods (1997-2000, 2001-2004, 2005-2008, 2009-2012, and 2013-2016) as well as for the longest period data is available (1997-20.., end date would e.g. be 2010 for CCI v0.1, but is 2016 for e.g. CCI v4.1). Note that in this case, data is not masked for common data availability. Whiskers show the median and the IQR. Above indicated the number of stations correlations were calculated for that comply to the following criteria: at least 10% of the timeseries is not NA, p-value < 0.05, and the calculated correlation is positive. And below indicated the number of years considered.