Soil moisture is a key variable in Earth systems, controlling the exchange of water and energy between land and atmosphere. Thus, understanding its spatiotemporal distribution and variability is important. Environment and Climate Change Canada (ECCC) has developed a new land surface parameterization, named the Soil, Vegetation, and Snow (SVS) scheme. The SVS land surface scheme features sophisticated parameterizations of hydrological processes, including water transport through the soil. It has been shown to provide more accurate simulations of the temporal and spatial distribution of soil moisture compared to the current operational land surface scheme. Simulation of high resolution soil moisture at the field scale remains a challenge. In this study, we simulate soil moisture maps at a spatial resolution of 100 m using the SVS land surface scheme over an experimental site located in Manitoba, Canada. Hourly high resolution soil moisture maps were produced between May and November 2015. Simulated soil moisture values were compared with estimated soil moisture values using a hybrid retrieval algorithm developed at Agriculture and Agri-Food Canada (AAFC) for soil moisture estimation using RADARSAT-2 Synthetic Aperture Radar (SAR) imagery. Statistical analysis of the results showed an overall promising performance of the SVS land surface scheme in simulating soil moisture values at high resolution scale. Investigation of the SVS output was conducted both independently of the soil texture, and as a function of the soil texture. The SVS model tends to perform slightly better over coarser textured soils (sandy loam, fine sand) than finer textured soils (clays). Correlation values of the simulated SVS soil moisture and the retrieved SAR soil moisture lie between 0.753–0.860 over sand and 0.676-0.865 over clay, with goodness of fit values between 0.567–0.739 and 0.457–0.748, respectively. The Root Mean Square Difference (RMSD) values range between 0.058–0.062 over sand and 0.055–0.113 over clay, with a maximum absolute bias of 0.049 and 0.094 over sand and clay, respectively. The unbiased RMSD values lie between 0.038–0.057 over sand and 0.039–0.064 over clay. Furthermore, results show an Index of Agreement (IA) between the simulated and the derived soil moisture always higher than 0.90.

This paper compares two data assimilation methods: state–parameter assimilation and output assimilation in improving streamflow forecasting using the Soil and Water Assessment Tool (SWAT) model. The state–parameter assimilation is performed by updating the stored water content and soil curve number with the extended Kalman filter (EKF); the output assimilation is carried out by updating the model output errors with autoregressive (AR) models. The performances of the two data assimilation techniques are compared for a dry year and a wet year, and it is found that whereas both methods significantly improve forecasting accuracy, their performances are influenced by the hydrological regime of the particular year. During the wet year, the average root-mean-square error (RMSE) for seven days forecasts is improved from 670.46 to 420.42 m3/s when output assimilation is used, and to 367.60 m3/s when state–parameter assimilation is used. The Nash–Sutcliffe coefficient (NSC) is improved from 0.63 to 0.85 a...

This paper presents the assimilation of synthetic surface soil moisture retrievals and C‐band backscatter signal in a 100‐meter resolution version of the Canadian Land Data Assimilation System (CaLDAS) on footprint scale soil moisture with a time interval of three hours. The synthetic surface soil moisture map was generated by extrapolating a regression relationship between in situ measurements and open loop land surface model outputs based on the soil texture of a given pixel. The surface roughness was inverted from RADARSAT‐2 imagery using a modified Integral Equation Model (IEM) model. Three hourly synthetic backscatter maps were created from this surface roughness and the synthetic soil moisture. The Ensemble Kalman filter (EnKF) with bias correction was applied to mitigate the impact of nonlinear errors introduced by multi‐sourced perturbations. Both time series and spatial maps were examined in the evaluation of the assimilation experiments. Results show that the assimilation of backscatter is as effective as assimilating soil moisture retrievals although the later has slightly better temporal statistics. Compared to the open loop, both approaches improved the analysis of surface and root zone soil moisture with significantly lower bias. For the later, the open loop average bias was reduced from −1.25 vol/vol to 0.59 vol/vol by backscatter assimilation and to 0.41 vol/vol by soil moisture assimilation.