Causes of freezing rain and snow disasters in South China

Snow and ice disasters are common, and La Nina phenomenon is the main cause of low temperature snow and ice disasters. China has a continental monsoon climate. The variability of weather and climate factors in winter and spring is large, which leads to various ice and snow disasters every year. Under the influence of global climate change, the factors of rain and snow freezing disasters are complex, and it is more difficult to forecast rain and snow. Floods caused by melting glaciers and mountain snow. Its formation is closely related to meteorological conditions. Every spring, the temperature rises, the snow area shrinks, glacier ice is exposed, glaciers begin to melt, and the flow in the valley continues to increase. In summer, the melting amount of ice and snow increases sharply, forming a summer flood peak; The melting in autumn is weakened and the flood peak is attenuated; In winter, it is freezing, melting stops and the valley is cut off. Melting water from snow and ice mainly causes disasters to highways. During the flood, the melting water of ice and snow carried a lot of sediment and silted ditches and bridges, which led to the blockage of culverts or bridges, resulting in flood overflow and blocked roads. Snow and ice disasters mostly occur in mountainous areas, and generally have little direct impact on people and industrial and agricultural production. Its greatest harm is the impact on highway transportation, resulting in a series of indirect losses. In order to prevent the damage caused by the melting of snow and ice, it is mainly to take appropriate blocking measures and build concrete dams and grid dams in the ditch. On the one hand, it can prevent sediment and gravel from leaving the ditch, on the other hand, it can stabilize the ditch bed and slope and reduce sediment erosion after plugging materials are piled up.