A possible solution for the problem of estimating the error structure of global soil moisture data sets

Abstract

In the last few years, research made significant progress towards operational soil moisture remote sensing which lead to the availability of several global data sets. For an optimal use of these data, an accurate estimation of the error structure is an important condition. To solve for the validation problem we introduce the triple collocation error estimation technique. The triple collocation technique is a powerful tool to estimate the root mean square error while simultaneously solving for systematic differences in the climatologies of a set of three independent data sources. We evaluate the method by applying it to a passive microwave (TRMM radiometer) derived, an active microwave (ERS‐2 scatterometer) derived and a modeled (ERA‐Interim reanalysis) soil moisture data sets. The results suggest that the method provides realistic error estimates.

Validation Analysis of SMAP and AMSR2 Soil Moisture Products over the United States Using Ground-Based Measurements

“…Four statistics were used, including the mean difference (MD), the root mean squared difference (RMSD), the unbiased root mean square error (ubRMSE) and the correlation coefficient (R). Triple collocation (TC) method was also used for analyzing the uncertainty of the two satellite-based soil moisture products and the in situ data sets [9,32,35].…”

“…The TC method provided an effective technique to perform the satellite-based soil moisture validation [9,35]. The TC model was introduced by [31] to calibrate scatterometer-derived ocean winds and estimate errors.…”

Recent decline in the global land evapotranspiration trend due to limited moisture supply

“…Satellite microwave remote sensing provides consistent large-scale information on soil moisture, although these sensors are only sensitive to the moisture of the upper few centimetres of the soil and the associated uncertainties are large for regions of dense vegetation 14 . The Tropical Rainfall Measuring Mission's (TRMM) microwave imager currently yields the longest high-quality record of surface soil moisture since 1998 (ref.…”

JASMIN: A prototype high resolution soil moisture analysis system for Australia

“…For surface soil wetness, verification McColl et al (2014) have developed the Extended Triple Collocation (ETC) method to estimate the temporal correlation between a model or observation system and the unknown truth. The ETC method makes the same assumptions as the more widely known Triple Collocation (TC; Scipal et al 2008;Vogelzang and Stoffelen 2012;Zwieback et al 2012;Dorigo et al 2010;Yilmaz and Crow 2014;Gruber et al 2016;Draper et al 2013) method. ETC and TC require three mutually independent time-series estimates of the same quantity.…”