Evaluation of Multiple Downscaled Microwave Soil Moisture Products over the Central Tibetan PlateauReport as inadecuate


Evaluation of Multiple Downscaled Microwave Soil Moisture Products over the Central Tibetan Plateau


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1

School of Resource and Environmental Science, Wuhan University, Wuhan 430079, China

2

School of Resource and Civil Engineering, Wuhan Institute of Technology, Wuhan 430205, China

3

State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China





*

Author to whom correspondence should be addressed.



Academic Editors: Nicolas Baghdadi, Xiaofeng Li and Prasad S. Thenkabail

Abstract Downscaled microwave soil moisture SM products with a fine resolution are of great importance for both local and regional studies. However, few studies have explored the merits of multiple downscaled microwave SM products. An evaluation of the different products could help to advance knowledge of the downscaled microwave SM products and help researchers to choose the appropriate downscaled SM products for use in further studies. In this research, five microwave SM products derived from Advanced Microwave Scanning Radiometer–Earth Observing System AMSR-E, AMSR2, and Soil Moisture and Ocean Salinity SMOS data were downscaled via the back-propagation neural network BPNN. The BPNN was chosen because it can effectively simulate the nonlinear relationship between SM and the land surface temperature LST-vegetation index VI. The different downscaled SM products were evaluated with in-situ SM data from the central Tibetan Plateau Soil Moisture-Temperature Monitoring Network SMTMN during the period from 1 August 2010 to 31 December 2012. Compared with the regression technique, the downscaled correlation coefficient r is significantly improved by the BPNN. The downscaled root-mean-square error RMSE and bias are comparable for the two techniques. As expected, LST and enhanced VI EVI are physically related to SM, and this is the most suitable combination for SM downscaling. Except for the ascending node of SMOS and AMSR2, the downscaled r is closely related to the original RMSE, and a lower original RMSE for the SM product results in a higher downscaled r. The BPNN-downscaled SMOS product in descending node is the closest to the in-situ SM among the different downscaled microwave SM products. The temporal variations and ranges of the microwave SM products are well maintained by the BPNN downscaling. Furthermore, the evaluations against in-situ SM reveal that the overall accuracies of the BPNN-downscaled SM products are very close to the original microwave SM products. View Full-Text

Keywords: evaluation; downscaling; back-propagation neural network BPNN; passive microwave soil moisture products evaluation; downscaling; back-propagation neural network BPNN; passive microwave soil moisture products





Author: Hongtao Jiang 1, Huanfeng Shen 1,* , Huifang Li 1, Fangni Lei 1, Wenxia Gan 2 and Liangpei Zhang 3

Source: http://mdpi.com/



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