Evaluating Consistency between the Remotely Sensed Soil Moisture and the Hydrological Model-Simulated Soil Moisture in the Qujiang Catchment of China

Lihua Xiong,Chong-Yu Xu,Ling Zeng,Han Yang

doi:10.3390/w10030291

Abstract

Accurate soil moisture estimation plays a crucial role in agricultural management and hydrological studies. Considering the scarcity of direct in-situ measurements, it is important to evaluate the consistency of soil moisture data acquired in indirect ways, including both satellite products and simulation values obtained via hydrological models. In this study, two types of high spatial-resolution remotely sensed values, namely the surface soil moisture (SSM) and the profile soil water index (SWI), are estimated from each of the ASCAT-A, ASCAT-B, SMAP and SMOS microwave satellites. They are compared with two groups of model-simulated daily soil moisture values, which are obtained by implementing the lumped Xinanjiang (XAJ) model and the DEM-based distributed hydrological model (DDRM) across the Qujiang catchment, located in southwest China. The results indicate that for each satellite product, SWI values always show closer agreement with model-simulated soil moisture values than SSM values, and SWI values estimated from ASCAT products perform best in terms of correlation coefficient with the model-simulated soil moisture, at around 0.8 on average, followed by the SMAP product, which shows a correlation coefficient of 0.48 on average, but the SMOS product shows poor performance. This evaluation of consistency provides useful information on their systematic differences and suggests subsequent studies to ensure their reconciliation in long-term records.

Highlights

As a key component in the hydrological cycle, soil moisture plays a crucial role in atmosphere-land surface interactions through controlling the available energy exchange among the hydrosphere, the atmosphere and the biosphere [1]
All surface soil moisture (SSM) information across the Qujiang catchment is acquired from remotely sensed soil moisture products
The evaluation of soil water index (SWI) data is obtained from maximizing the overall correlation coefficient R between catchment-wide remotely sensed averages and model-simulated averages by varying the T parameter of the exponential filter from 1 to 100 days at a step of 1 day

Summary

Introduction

As a key component in the hydrological cycle, soil moisture plays a crucial role in atmosphere-land surface interactions through controlling the available energy exchange among the hydrosphere, the atmosphere and the biosphere [1]. Continuous and accurate acquisition of soil moisture data at local, regional and global scales is of vital importance for simulation of the climate system and the. Current ways to obtain soil moisture fail to satisfy all these needs. Soil moisture information can be obtained in both direct and indirect ways. The direct field measurements of soil moisture are thought to be fairly accurate, but are costly, with small coverage areas, and only provide point-based measurements rather than areal values, which are of more interest for practical applications. Indirect acquisition ways, including remote sensing (optical, thermal infrared and microwave) and hydrological models (either the physically-based land-surface models, or rainfall-runoff hydrological models), offer the possibility to provide the areal soil moisture information on a low-cost basis, but with less accuracy than ground point measurements [2,3]

Methods

Results

Conclusion