4:30 PM - 4:45 PM
[STT40-11] Analysis of the Relationship Between Backscatter Intensity of L-band SAR and Snow Depth Using Indoor Radio Wave Testing and ALOS-2 Observations
Keywords:Hokkaido, Corner Reflecter, Vector Network Analyzer, Satellite Remote Sensing
Observing the spatial distribution of snow cover is crucial for understanding the water cycle and water resources. Synthetic Aperture Radar (hereafter "SAR") mounted on satellites has been used for snow observation in previous studies (e.g., Tadono et al., 2002). Among various SAR wavelengths, L-band SAR, which has a relatively long wavelength, exhibits higher penetration through snow, allowing for the observation of deeper snowpack compared to X-band or C-band SAR. However, studies using L-band SAR for snow observation are less common than those using other wavelengths (Tsai et al., 2019), highlighting the need for further application and validation studies in this field.
In our study, we installed a snow depth gauge next to a corner reflector (hereafter "CR") set up by JAXA in Tomakomai, Hokkaido (Figure 1). We analyzed the relationship between the backscattering intensity observed by ALOS-2 at the CR and the measured snow depth. Additionally, to verify the validity of the backscattering intensity observed by ALOS-2, we conducted laboratory experiments on the variation of backscattering intensity caused by snow using an anechoic chamber and a vector network analyzer (hereafter "VNA") owned by the Hokkaido Research Organization (Figure 2). All ALOS-2 data used in this study were acquired in the right-looking, descending orbit during daytime (Table 1).
Figure 3 shows the backscattering intensity images of the CR observed by ALOS-2. The CR reflection is distinct in the snow-free image; however, it becomes indistinct when the snow depth reaches 37.8 cm (No.4). Figure 4 plots the relationship between snow depth and the backscattering intensity observed by ALOS-2 (green) and VNA (blue; 1.26GHz). Figure 4 suggests that ALOS-2 is more sensitive to snow cover than VNA. However, further analysis is needed to determine whether a simple linear regression is appropriate for modeling this relationship. Nonetheless, the backscattering intensity decreases as snow depth increases (indicating a negative correlation), suggesting microwave attenuation due to snow cover.
Nagai et al. (2018) reported a positive correlation between the backscattering intensity of ALOS-2 and snow depth observed during daytime. However, in this study, we found a negative correlation between backscattering intensity and snow depth in both ALOS-2 observations and VNA experiments. The reason for the positive correlation found in previous studies remains unclear. However, factors such as the dielectric properties of snow, volume scattering, and double scattering of microwaves may have influenced the results. These factors should be investigated in future research.
Acknowledgments
The ALOS-2 data used in this study were provided under the 3rd Earth Observation Research Announcement by JAXA.
References
Nagai et al. (2018) Development of snow-depth map using ALOS-2. JpGU Meetin 2018, ACC28-04.
Tadono et al. (2002) Proceedings of Hydraulic Engineering, https://doi.org/10.2208/prohe.46.37
Tsai et al. (2019) Remote Sens., https://doi.org/10.3390/rs11121456
In our study, we installed a snow depth gauge next to a corner reflector (hereafter "CR") set up by JAXA in Tomakomai, Hokkaido (Figure 1). We analyzed the relationship between the backscattering intensity observed by ALOS-2 at the CR and the measured snow depth. Additionally, to verify the validity of the backscattering intensity observed by ALOS-2, we conducted laboratory experiments on the variation of backscattering intensity caused by snow using an anechoic chamber and a vector network analyzer (hereafter "VNA") owned by the Hokkaido Research Organization (Figure 2). All ALOS-2 data used in this study were acquired in the right-looking, descending orbit during daytime (Table 1).
Figure 3 shows the backscattering intensity images of the CR observed by ALOS-2. The CR reflection is distinct in the snow-free image; however, it becomes indistinct when the snow depth reaches 37.8 cm (No.4). Figure 4 plots the relationship between snow depth and the backscattering intensity observed by ALOS-2 (green) and VNA (blue; 1.26GHz). Figure 4 suggests that ALOS-2 is more sensitive to snow cover than VNA. However, further analysis is needed to determine whether a simple linear regression is appropriate for modeling this relationship. Nonetheless, the backscattering intensity decreases as snow depth increases (indicating a negative correlation), suggesting microwave attenuation due to snow cover.
Nagai et al. (2018) reported a positive correlation between the backscattering intensity of ALOS-2 and snow depth observed during daytime. However, in this study, we found a negative correlation between backscattering intensity and snow depth in both ALOS-2 observations and VNA experiments. The reason for the positive correlation found in previous studies remains unclear. However, factors such as the dielectric properties of snow, volume scattering, and double scattering of microwaves may have influenced the results. These factors should be investigated in future research.
Acknowledgments
The ALOS-2 data used in this study were provided under the 3rd Earth Observation Research Announcement by JAXA.
References
Nagai et al. (2018) Development of snow-depth map using ALOS-2. JpGU Meetin 2018, ACC28-04.
Tadono et al. (2002) Proceedings of Hydraulic Engineering, https://doi.org/10.2208/prohe.46.37
Tsai et al. (2019) Remote Sens., https://doi.org/10.3390/rs11121456