scholarly journals Soil Moisture Retrievals Using Multi-Temporal Sentinel-1 Data over Nagqu Region of Tibetan Plateau

2021 ◽  
Vol 13 (10) ◽  
pp. 1913
Author(s):  
Mengying Yang ◽  
Hongquan Wang ◽  
Cheng Tong ◽  
Luyao Zhu ◽  
Xiaodong Deng ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
Cloud Model ◽  
Roughness Parameter ◽  
Optical Data ◽  
The Tibetan Plateau ◽  
Modis Ndvi ◽  
Multi Temporal ◽  
Vegetation Water ◽  
Semi Empirical

This paper presents an approach for retrieval of soil moisture in Nagqu region of Tibetan Plateau using VV-polarized Sentinel-1 SAR and MODIS optical data, by coupling the semi-empirical Oh-2004 model and the Water Cloud Model (WCM). The Oh model is first used to estimate the surface roughness parameter based on the hypothesis that the roughness is invariant among SAR acquisitions. Afterward, the vegetation water content (VWC) in the WCM is calculated from the daily MODIS NDVI data obtained by temporal interpolation. To improve the performance of the model, the parameters A, B, and α of the WCM are analyzed and optimized using randomly selected half of the sampled dataset. Then, the soil moisture is retrieved by minimizing a cost function between the simulated and measured backscattering coefficients. The comparison of the retrieved soil moisture with the ground measurements shows the determination coefficient R2 and the Root Mean Square Error (RMSE) are 0.46 and 0.08 m3/m3, respectively. These results demonstrate the capability and reliability of Sentinel-1 SAR data for estimating the soil moisture over the Tibetan Plateau.

scholarly journals Soil Moisture Retrieval from the Chinese GF-3 Satellite and Optical Data over Agricultural Fields

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2675 ◽  
Author(s):  
Linlin Zhang ◽  
Qingyan Meng ◽  
Shun Yao ◽  
Qiao Wang ◽  
Jiangyuan Zeng ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Satellite Data ◽  
Cloud Model ◽  
Vegetation Indices ◽  
Bare Soil ◽  
Optical Data ◽  
Retrieval Algorithm ◽  
Landsat 8 ◽  
Backscattering Coefficient ◽  
Vegetation Water

Timely and accurate soil moisture information is of great importance in agricultural monitoring. The Gaofen-3 (GF-3) satellite, the first C-band multi-polarization synthetic-aperture radar (SAR) satellite in China, provides valuable data sources for soil moisture monitoring. In this study, a soil moisture retrieval algorithm was developed for the GF-3 satellite based on a backscattering coefficient simulation database. We adopted eight optical vegetation indices to determine the relationships between these indices and vegetation water content (VWC) by combining Landsat-8 data and field measurements. A backscattering coefficient database was built using an advanced integral equation model (AIEM). The effects of vegetation on backscattering coefficients were corrected using the water cloud model (WCM) to obtain the bare soil backscattering coefficient ( σ s o i l ° ). Then, soil moisture retrievals were obtained at HH, VV and HH+VV combination respectively by minimizing the observed bare soil backscattering coefficient ( σ s o i l ° ) and the AIEM-simulated backscattering coefficient ( σ soil-simu ° ). Finally, the proposed algorithm was validated in agriculture region of wheat and corn in China using ground soil moisture measurements. The results showed that the normalized difference infrared index (NDII) had the best fit with measured VWC values (R = 0.885) among the eight vegetation water indices; thus, it was adopted to correct the effects of vegetation. The proposed algorithm using GF-3 satellite data performed well in soil moisture retrieval, and the scheme combining HH and VV polarization exhibited the highest accuracy, with a root mean square error (RMSE) of 0.044 m3m−3, followed by HH polarization (RMSE = 0.049 m3m−3) and VV polarization (RMSE = 0.053 m3m−3). Therefore, the proposed algorithm has good potential to operationally estimate soil moisture from the new GF-3 satellite data.

The South Asia Monsoon Break Promotes Grass Growth on the Tibetan Plateau

2021 ◽  
Author(s):  
Yanghang Ren ◽  
Kun Yang ◽  
Han Wang
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
Solar Radiation ◽  
Climate Variability ◽  
South Asia ◽  
The Tibetan Plateau ◽  
The South ◽  
Central Eastern ◽  
Grass Growth ◽  
The Impact

<p>As region that is highly sensitive to global climate change, the Tibetan Plateau (TP) experiences an intra-seasonal soil water deficient due to the reduced precipitation during the South Asia monsoon (SAM) break. Few studies have investigated the impact of the SAM break on TP ecological processes, although a number of studies have explored the effects of inter-annual and decadal climate variability. In this study, the response of vegetation activity to the SAM break was investigated. The data used are: (1) soil moisture from in situ, satellite remote sensing and data assimilation; and (2) the Normalized Difference Vegetation Index (NDVI) and Solar-Induced chlorophyll Fluorescence (SIF). We found that in the region impacted by SAM break, which is distributed in the central-eastern part of TP, photosynthesis become more active during the SAM break. And temporal variability in the photosynthesis of this region is controlled mainly by solar radiation variability and has little sensitivity to soil moisture. We adopted a diagnostic process-based modeling approach to examine the causes of enhanced plant activity during the SAM break on the central-eastern TP. Our analysis indicates that active photosynthetic behavior in the reduced precipitation is stimulated by increases in solar radiation absorbed and temperature. This study highlights the importance of sub-seasonal climate variability for characterizing the relationship between vegetation and climate.</p>

Sampling depth of L-band radiometer measurements of soil moisture and freeze-thaw dynamics on the Tibetan Plateau

2019 ◽  
Vol 226 ◽  
pp. 16-25 ◽  
Author(s):  
Donghai Zheng ◽  
Xin Li ◽  
Xin Wang ◽  
Zuoliang Wang ◽  
Jun Wen ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
The Tibetan Plateau ◽  
Sampling Depth ◽  
Freeze Thaw ◽  
L Band ◽  
Band Radiometer

Pedogenesis, permafrost, and soil moisture as controlling factors for soil nitrogen and carbon contents across the Tibetan Plateau

2009 ◽  
Vol 15 (12) ◽  
pp. 3001-3017 ◽  
Author(s):  
FRANK BAUMANN ◽  
JIN-SHENG HE ◽  
KARSTEN SCHMIDT ◽  
PETER KÜHN ◽  
THOMAS SCHOLTEN
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
Soil Nitrogen ◽  
Controlling Factors ◽  
The Tibetan Plateau

Comparisons of remote sensing and reanalysis soil moisture products over the Tibetan Plateau, China

2018 ◽  
Vol 146 ◽  
pp. 110-121 ◽  
Author(s):  
Waheed Ullah ◽  
Guojie Wang ◽  
Zhiqiu Gao ◽  
Daniel Fiifi T. Hagan ◽  
Dan Lou
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Tibetan Plateau ◽  
The Tibetan Plateau
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