[A-CC32] 雪氷学

[ACC32-10] Spatial Dynamics of Urban Icing and Its Societal Impact (A Case Study of Ulaanbaatar, Mongolia)

*Ganbold Ulambayar^1,2、Nakamura Dai¹、Avirmed Dashtseren^2,3、Watanabe Tatsuya¹、Yamkhin Jambaljav⁴、Ganbold Byambabayar⁵、Khurelbaatar Temuujin²、Gansukh Tsogt-Erdene²、Dagvadorj Otgonjargal¹ (1.Kitami Institute of Technology、2.Institute of Geography and Geoecology, Mongolian Academy of Sciences、3.UNESCO Chair of Environmental Sciences in Eastern Central Asia、4.Geocryo LLC、5.National University of Mongolia)

キーワード：Icing、Spatial distribution、Natural factors、Snow cover、n-factor、Remote sensing

Understanding the icing process is crucial for preventing and mitigating the geo-hazards it can create. Icing is a complex phenomenon influenced by various natural factors, and our knowledge in this field remains limited. This study focused on the multi-year dynamics of icing formations and the natural factors that affect them in Ulaanbaatar, the capital and most populous city of Mongolia, where icing occurs annually. We analyzed the long-term dynamics of icing using Landsat satellite data from 2009 to 2024. The air temperature regime does not significantly impact icing dynamics, while precipitation amounts clearly impact it. Over the past 14 years, the icing area has fluctuated between 0.79 and 2.87 hectares. However, during the winter of 2023-2024, the spatial distribution of icing changed, expanding to a total of 4.40 hectares in the settlement area. This shift has caused significant damage to households in the affected regions. The change in the spatial distribution of icing is related to alterations in the ground surface temperature regime due to the insulating effect of winter snow cover. As a result, spring water, the main source of icing, flowed over the ground surface and accumulated in the settlement area, forming icing. Additionally, the increase in the icing area was related to the precipitation amount before icing and the geological conditions of the area. Precipitation before icing formation raised the soil water level, causing soil water to emerge on the surface when the ground froze in winter, thus expanding the icing area. This soil water came from the pit latrine and the area under the yurt. The hollow spaces at the top of pit latrines allowed soil water to rise to the surface easily. However, the ground under the yurt remained unfrozen during winter, depending on the indoor temperature, allowing soil water to rise to the surface. In Ulaanbaatar, the lack of infrastructure leads residents of affected areas to dispose of wastewater from human activities in pit latrines, contributing to soil water contamination. Consequently, this contaminated soil water serves as an additional source of icing, which may pose health risks not only to local residents but also to the capital's population.