5:15 PM - 6:30 PM
[ACC25-P03] Preliminary observation report of snow-buried corner reflectors for SAR-based snow-depth monitoring in Nagaoka, Niigata (2020/2021)
Keywords:SAR, Snow depth, Extreme weather, PALSAR-2
Understanding the distribution of snow depth over a wide area is basic information for disaster prevention. The number of ground-based observation points is limited especially in mountainous areas with heavy snowfall, therefore further development of observation systems is expected. Satellite-based synthetic aperture radars (SARs) are expected to observe a wide area and generate detailed information of snow depth distribution in such an area. SAR backscatter amplitude is decreased by snowpack, because reflection and scattering occur on the surface and inside of the snow cover. The backscatter amplitude is considered to depend on the depth and physical properties (water content) of the snow layer.
In this study, metal-made Corner Reflectors (CRs) for SAR are built and buried in actual snowpack. The signal on the CRs is significantly stronger than the surroundings. Using these, we aim to understand the microwave-propagation process in more detail and with lower noise than before.
The CRs are built with three 1-m squared panels. Steel-made CRs are made for extremely heavy snowpack (>3 m) in addition to stainless-made one. Totally four CRs are set in experimental fields operated by the National Research Institute for Earth Science and Disaster Resilience (NIED) in Nagaoka, Niigata Prefecture. CR installation was completed in November 2019. In addition, real-time camera monitoring system were installed and started on December 2020, which enables image transmission of snow-burring CRs in every 30-min. or 1-hours.
Significant heavy snowfall in a short time occurred on around December 14, 2021 around Niigata, Japan. This event caused social affects, for example, hundreds of cars getting stuck on the highway for a long time. The CR cameras captured the sudden increase of snow depth. Snow depth has not been lower than 50 cm in Nagaoka and not been lower than 1 m in Tochio-tashiro since this time. Regular automatic snow-depth measurement is operated at both points, but the snow depth is not completely uniform around the area. There is a slight spatial-heterogeneity caused by the shade, ground features, and wind direction. Especially in Nagaoka, the snow depth increases and decreases around 1 m, the CR’s height. Because whether the CR is completely buried or partially exposed is important information in later analysis, the image from the camera shows the situation most reliably.
While recording the snow condition of CR, the Sentinel-1a/b satellites of the European Space Agency are conducting observations in multiple satellites/orbits, deriving three times observation opportunity in 12days for our study sites. In addition, Japanese SAR satellite "DAICHI-2" is scheduled to carry out observations twice in February in the high-resolution mode. In this presentation, we will analyze these satellite observation data and CR snow cover conditions, and give a preliminary report of the obtained results.
In this study, metal-made Corner Reflectors (CRs) for SAR are built and buried in actual snowpack. The signal on the CRs is significantly stronger than the surroundings. Using these, we aim to understand the microwave-propagation process in more detail and with lower noise than before.
The CRs are built with three 1-m squared panels. Steel-made CRs are made for extremely heavy snowpack (>3 m) in addition to stainless-made one. Totally four CRs are set in experimental fields operated by the National Research Institute for Earth Science and Disaster Resilience (NIED) in Nagaoka, Niigata Prefecture. CR installation was completed in November 2019. In addition, real-time camera monitoring system were installed and started on December 2020, which enables image transmission of snow-burring CRs in every 30-min. or 1-hours.
Significant heavy snowfall in a short time occurred on around December 14, 2021 around Niigata, Japan. This event caused social affects, for example, hundreds of cars getting stuck on the highway for a long time. The CR cameras captured the sudden increase of snow depth. Snow depth has not been lower than 50 cm in Nagaoka and not been lower than 1 m in Tochio-tashiro since this time. Regular automatic snow-depth measurement is operated at both points, but the snow depth is not completely uniform around the area. There is a slight spatial-heterogeneity caused by the shade, ground features, and wind direction. Especially in Nagaoka, the snow depth increases and decreases around 1 m, the CR’s height. Because whether the CR is completely buried or partially exposed is important information in later analysis, the image from the camera shows the situation most reliably.
While recording the snow condition of CR, the Sentinel-1a/b satellites of the European Space Agency are conducting observations in multiple satellites/orbits, deriving three times observation opportunity in 12days for our study sites. In addition, Japanese SAR satellite "DAICHI-2" is scheduled to carry out observations twice in February in the high-resolution mode. In this presentation, we will analyze these satellite observation data and CR snow cover conditions, and give a preliminary report of the obtained results.