Acta Geodaetica et Cartographica Sinica ›› 2021, Vol. 50 ›› Issue (7): 905-915.doi: 10.11947/j.AGCS.2021.20200125

• Photogrammetry and Remote Sensing • Previous Articles     Next Articles

The co-polarized phase difference model for dry snow depth inversion

SONG Yina1, XIAO Pengfeng1,2,3, ZHANG Xueliang1, ZHUO Yue1, MA Wei1   

  1. 1. School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China;
    2. Key Laboratory for Land Satellite Remote Sensing Applications of Ministry of Natural Resources, Nanjing 210023, China;
    3. Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, Nanjing 210023, China
  • Received:2020-04-14 Revised:2021-04-20 Published:2021-08-13
  • Supported by:
    The National Natural Science Foundation of China (No. 41671344);The National Basic Resource Survey Special (No. 2017FY100502)

Abstract: Snow depth is an important structure parameter of snow cover. Obtaining high-precision spatial distribution of snow depth is significant to regional water resources management, climate change research, and disaster prediction. Recently, the co-polarized phase difference (CPD) model based on the polarimetric synthetic aperture radar (PolSAR) technique has shown promising results regarding the dry snow depth estimation. The model is established based on the birefringent properties of snow and on the Maxwell-Garnett mixing formulas providing a link between the snow microstructure and CPD. In this study, the dry snow depth is computed using the PolSAR CPD method with C band GF-3 quad-polarization data and measured samples. The study area is selected from the upstream of Kelan River basin, which is located in the north Altai Mountains in Xinjiang, China. To improve the retrieving accuracy, we divide the study area into deep snow area and shallow snow area. The results show that: ①In the ideal case with constant snow anisotropic relative permittivity, CPD is only a function of snow depth. The semi-empirical linear fit model can be used to invert snow depth and the inversion accuracy is related to the window size of the Gaussian low-pass filter used in the CPD calculation. The optimal filter window in shallow snow area is 55×55 pixels and the corresponding accuracy is R=0.83 and RMSE=2.72 cm, and the optimal filter window in deep snow area is 37×37 pixels and the corresponding accuracy is R=0.54 and RMSE=11.69 cm. ②With the increase of slope, the inversion error of snow depth shows a trend of increasing. The inversion uncertainty is affected by the degree of snow metamorphism, water content of snow and the incidence angle. The inversion method is more applicable to the snow layers with dry, homogeneous and low metamorphic crystallization and the SAR with larger incidence angle. ③Compared with the existing CPD model-based snow depth inversion methods, the proposed inversion method has higher accuracy and reduces the required parameters for inversion. Therefore, this study shows the practicability of CPD model in the dry snow depth estimation over mountain areas and provides a new idea for improving snow depth accuracy using CPD models.

Key words: Kelan River, snow depth, SAR, snow microstructure, co-polarized phase difference

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