ABSTRACT

The high-resolution multi-temporal PlanetScope image of 7 February 2021 clearly shows the fall of a large part of the Nanda Ghunti glacier (Uttarakhand) down in the base of the valley from a height of about 2000 m. The recorded seismic signals at the local seismic networks, close to the Joshimath station, show the occurrence of the fall of the first glacier block followed by another block which corresponds to the seismic signal recorded the second time. The timings of signals recorded from the seismic station are related to the visual sign of local dust in the valley after the fall of the glacier blocks at 05:01 AM and 05:28 AM UTC on 7 February 2021. In the present paper, we carried out the changes in spectral signatures of PlanetScope imageries and backscattering coefficients from Sentinel-1 synthetic aperture radar (SAR) data at six different locations. Our analysis suggests pronounced changes at all locations based on spectral signatures and backscattering coefficients due to deposition of snow dust due to the fall of the glacier blocks. Changes in surface wetness are evident after the melting of snow due to the deposition of dust in the valley.

摘要

2021 年 2 月 7 日的高分辨率多时相 PlanetScope 图像清楚地显示了 Nanda Ghunti 冰川（北阿坎德邦）的大部分从大约 2000 米的高度下降到山谷底部。在靠近 Joshimath 台站的当地地震台网记录的地震信号显示，第一个冰川块随后发生了与第二次记录的地震信号相对应的另一个块的倒塌。地震台记录信号的时间与2021年2月7日UTC时间05:01 AM和05:28 AM UTC冰川块倒塌后山谷局部灰尘的视觉标志有关。 在本文中，我们对来自 Sentinel-1 合成孔径雷达 (SAR) 数据在六个不同位置的 PlanetScope 图像的光谱特征和反向散射系数进行了更改。我们的分析表明，根据光谱特征和后向散射系数，由于冰川块掉落导致雪尘沉积，所有位置都发生了显着变化。由于山谷中灰尘的沉积，雪融化后地表湿度的变化很明显。