An objective methodology for merging satellite- and model-based soil moisture products

An objective methodology that does not require any user-defined parameter assumptions is introduced to obtain an improved soil moisture product along with associated uncertainty estimates. This new product is obtained by merging model-, thermal infrared remote sensing-, and microwave remote sensing-based soil moisture estimates in a least squares framework where uncertainty estimates for each product are obtained using triple collocation. The merged anomaly product is validated against in situ based soil moisture data and shows higher correlations with observations than individual input products; however, it is not superior to a naively merged product acquired by averaging the products using equal weighting. The resulting combined soil moisture estimate is an improvement over currently available soil moisture products due to its reduced uncertainty and can be used as a standalone soil moisture product with available uncertainty estimates.