ALBERT

Description: This study explores the hazard of avalanches in high mountain Asia (HMA), an area that not only sustains livelihoods through water storage, but also holds potential for natural disasters. Although there is limited research on the complex relationship between climate and triggers of avalanches, this study reviews available literature to identify research gaps and proposes future directions for research and mitigation strategies. In this study, available literature was reviewed covering the period from the late 20th century to June 2022 to identify research and societal gaps and propose future directions of research and mitigation strategies. Beyond scientific literature, technical reports, newspapers, social media and other local sources were consulted to compile a comprehensive, open access and version-controlled database of avalanche events and their associated impacts. Over 681 avalanches with more than 3131 human fatalities were identified in eight countries of the region. Afghanistan has the highest recorded avalanche fatalities (1057) followed by India (952) and Nepal (508). Additionally, 564 people lost their lives while climbing peaks above 4500 m a.s.l., one third of which were hired staff. Although fatalities are significant, and local long-term impacts of avalanches may be considerable, so far, limited holistic adaptation or mitigation measures exist in the region. Considering the high impact avalanches have in the region we suggest to further develop adaptation measures including hazard zonation maps based on datasets of historic events and modelling efforts. More research studies should also be attempted to understand trends and drivers of avalanches in the region.

Description: In order to understand the dynamics of auroral structure formation in the magnetosphere-ionosphere (M-I) coupling system, global simulation studies of the feedback instability have been performed. However, most of the previous works are limited to arguments on the global characteristics of the auroral arc or the local analysis of fine structure formation such as curls or spirals. We have newly developed a nonlinear simulation code for the feedback instability in the dipole field configuration so as to investigate auroral structure formation including the fine structures in the global M-I coupling system. The new reduced magnetohydrodynamic (MHD) simulation code is implemented with a novel flux coordinate system adopted to the spherical boundary and efficient numerical discretization. Using the new simulation code, we have found that longitudinally elongated arc-like structure of the ionospheric density, electric field, and field-aligned current perturbations spontaneously grow due to the feedback instability. Furthermore, we have revealed that these structures are distorted by a secondary instability, leading to emergence of auroral fine structures. The sense of rotation and the scale of these fine vortex structures are qualitatively consistent with the curls, and the growth rate of the secondary instability is comparable to that of the Kelvin-Helmholtz instability owing to the perturbed E×B flow sheer induced by the feedback instability.

Description: Temporal variation of shallow subsurface structure is monitored by the SPAC-based method using a seismic array on a landslide area. We deployed a seismic array that consists of 14 three-component seismometers with a natural frequency of 4.5Hz on flat ground with diameters of 28m x 75m in a landslide area in the western part of Shizuoka prefecture, Japan. We used the data from October 2020 to May 2022. We applied the SPAC method using ambient noise data. The SPAC is obtained for each day and temporal variations are investigated. We compared the daily SPAC with the reference SPAC, which is obtained by stacking all the daily SPAC. The results show a characteristic change in SPAC that includes weekly changes, rainfall-related changes, and seasonal changes. In the weekly changes, a systematic difference is found between weekends and weekdays. Regarding the rainfall-related change, the large vibration, which has a significant impact on SPAC analysis, by a stream near the array is often observed during/after heavy rain. We statistically estimated and removed the effect of these two changes to monitor the variation due to the subsurface structure. We found the SPAC in the high-frequency region decreases due to rainfall, which is regarded as being due to a rise in the groundwater level caused by rainfall. MMSPAC (multimode spatial autocorrelation) method (Asten.2006, Ikeda.2012) is used to estimate the most strongly affected depth ranges to compare the structure model using reference SPAC. The seasonal change may be associated with the state of the shallow groundwater.