Paper Info
Title
Mapping High Spatiotemporal-Resolution Soil Moisture By Upscaling Sparse Ground-Based Observations Using A Bayesian Linear Regression Method For Comparison With Microwave Remotely Sensed Soil Moisture Products
Abstract
In recent decades, microwave remote sensing (RS) has been used to measure soil moisture (SM). Long-term and large-scale RS SM datasets derived from various microwave sensors have been used in environmental fields. Understanding the accuracies of RS SM products is essential for their proper applications. However, due to the mismatched spatial scale between the ground-based and RS observations, the truth at the pixel scale may not be accurately represented by ground-based observations, especially when the spatial density of in situ measurements is low. Because ground-based observations are often sparsely distributed, temporal upscaling was adopted to transform a few in situ measurements into SM values at a pixel scale of 1 km by introducing the temperature vegetation dryness index (TVDI) related to SM. The upscaled SM showed high consistency with in situ SM observations and could accurately capture rainfall events. The upscaled SM was considered as the reference data to evaluate RS SM products at different spatial scales. In regard to the validation results, in addition to the correlation coefficient (R) of the Soil Moisture Active Passive (SMAP) SM being slightly lower than that of the Climate Change Initiative (CCI) SM, SMAP had the best performance in terms of the root-mean-square error (RMSE), unbiased RMSE and bias, followed by the CCI. The Soil Moisture and Ocean Salinity (SMOS) products were in worse agreement with the upscaled SM and were inferior to the R value of the X-band SM of the Advanced Microwave Scanning Radiometer 2 (AMSR2). In conclusion, in the study area, the SMAP and CCI SM are more reliable, although both products were underestimated by 0.060 cm(3) cm(-3) and 0.077 cm(3) cm(-3,) respectively. If the biases are corrected, then the improved SMAP with an RMSE of 0.043 cm(3) cm(-3) and the CCI with an RMSE of 0.039 cm(3) cm(-3) will hopefully reach the application requirement for an accuracy with an RMSE less than 0.040 cm(3) cm(-3).
Year
DOI
Venue
2021
10.3390/rs13020228
REMOTE SENSING
Keywords
DocType
Volume
error, remote sensing product, soil moisture, upscaling, validation
Journal
13
Issue
Citations 
PageRank 
2
0
0.34
References 
Authors
0
4
Name
Order
Citations
PageRank
Jian Kang100.34
Rui Jin200.68
Xin Li300.34
Yang Zhang418943.34