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Tytuł pozycji:

Applications of Synthetic Aperture Radar Data to study Permafrost Active Layer and Wetland Water Level Changes

Tytuł :
Applications of Synthetic Aperture Radar Data to study Permafrost Active Layer and Wetland Water Level Changes
Autorzy :
Jia, Yuanyuan
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Temat :
Synthetic Aperture Radar Data
Permafrost Active Layer Changes
Wetland Water Level Changes
Dysertacja/Praca dyplomowa
Synthetic aperture radar (SAR) and Interferometry SAR (InSAR) have been widely used for Earth surface deformation studies and the associated Earth science research and applications, such as earthquakes, volcano eruptions, landslides and glacier movements. In this study, we conduct two Earth science studies using SAR and InSAR data from the L-band Synthetic Aperture Radar (PALSAR) onboard the Advanced Land Observing Satellite (ALOS). First, we quantified the Active Layer Thickness (ALT) and ALT changes over the northern Qinghai-Tibetan plateau (QTP) using InSAR data. Because of its unique topography and terrains, the QTP is covered by a large layer of discontinuous and sporadic alpine permafrost which has degraded about 10% during the past few decades due primarily to global warming. Based on previous results from in situ observations of monitoring sites, climate-driven models, and SBAS-InSAR observations, the averaged active layer thickness along the Qinghai-Tibet railway (QTR) ranges from less than 1 m to more than 5 m. The rate of increase of the ALT is approximately 6.3 cm·yr-1 from 2006 to 2010, and the signal exhibits extensive temporal and spatial variability. In this study, we estimated the ALT and the thickening rate in the northern QTP near the railway using ALOS PALSAR L-band InSAR data observed land subsidence and ALT modeling. A linear relationship between the InSAR observed subsidence and ALT was tested and constructed. The ALT and ALT trends were simultaneously estimated with 30 m spatial resolution using the calibrated relationship. We found that the ALT is largely thickening, and with distinct spatial variations, for the first time, over a large permafrost-covered region of the northern Qinghai-Tibetan Plateau. The result of this study has implications of improving our understanding in the alpine surface and subsurface cryospheric-hydrologic processes, ecosystem change, runoff changes in headwaters for some of the largest rivers in Asia, and the stability of human infrastructures over the Qinghai-Tibetan Plateau.We further demonstrated that the wetland water level changes in the Sundarbans mangrove forest wetland, Bangladesh could be effectively observed by integrating L-band SAR intensity imagery and radar altimetry data. This technique is based on an assumption that the dominant backscattering mechanism in mangrove forests is double-bounce backscattering, at the same time, the double-bounce backscattering is weakened because of water level rising. In order to demonstrate this assumption, we computed interferogram coherence, a byproduct of InSAR processing, and averaged backscattering coefficient during wet season and dry season over our study regions. We assume that despite of taller mangrove trees (~10 m) in the Sundarbans, L-Band SAR data would achieve double bounce and thus interferogram coherence. We found that the L-band SAR backscatter coefficient in wetlands is inversely proportional with water level in the mangrove forest. The correlation between these two parameters over the Mangrove forest was high (> 0.9). Finally, the SAR backscattering coefficient is then used to estimate high-resolution (30 m) water level time series, covering the study region. SAR-inferred water level time series show significant spatial and temporal variability

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