Dynamic snowmelt process and its influencing factors in Hulun Buir forest region,Inner Mongolia
Snow plays a critical role in surface radiation,energy,and water cycles and is often used as an impor-tant indicator for global change assessment and monitoring. In northern pastoral areas of China,the winter snow depth and snow cover are extensive,with prolonged snow layer maintenance. Excessive snowfall can have disas-trous impacts on livestock production,while the meltwater from snow contributes to the improvement of the eco-logical and hydrological conditions. On the other hand,the speed of snowmelt is a crucial indicator for assessing the occurrence of snowmelt-induced floods. Therefore,snow accumulation and its melting process,along with the influencing factors,are not only focal points for various industries related to ecological and socioeconomic development,but they also have direct implications for disaster prevention and pattern recognition. Since 2020,meteorological departments in Inner Mongolia have successively established and applied a batch of field automat-ic snow depth observation instruments,enabling the continuous hourly observation of snow depth at multiple for-est land stations. This provides a valuable opportunity for analyzing the dynamic changes of snowmelt in forest land. Based on the hourly data from field automatic snow depth observation stations in Hulun Buir forest region of Inner Mongolia,this study,through the analysis of multiple locations and multiple snowmelt processes,as well as the results of regional common feature analysis,explores high-frequency dynamic snowmelt processes and their influencing factors. This research serves as a direct basis for a more accurate understanding of the dy-namic patterns of snowmelt in northern forest land and dynamic predictions. The results indicate:(1) Winter snow in Hulun Buir forest region can persist for about 102 to 155 days,generally entering the melting period in early March. The snowmelt process typically lasts for 5 to 18 days and can be divided into continuous and rapid melting stages. (2) When the snow depth is less than 3 cm,the ground snow cover rapidly enters the melting stage. If the average temperature between 10:00 and 20:00 is above 0 ℃,forest snow cover will completely melt within 36 hours. (3) Snowmelt exhibits a pattern of gradual decline followed by a rapid decline and then a slow decline during the day. Compared to grasslands,the peak snowmelt period is delayed and occurs between 10:00 and 15:00. Thermal conditions are the primary influencing factor for snowmelt in Hulun Buir forest re-gion,and when studying snow cover as the affected factor,it was found that the ground temperature at 14:00 is the dominant factor affecting the snowmelt process and rate. (4) Although temperature and snow surface temper-ature are closely related to snowmelt,ground temperature emerges as the most sensitive factor influencing snow-melt response during the snowmelt process. Ground temperature at 0 cm,at 14:00 and 18:00,is the key factor determining or affecting the snowmelt process and rate in the northern forest land of China. Additionally,snow-melt is largely determined by thermal conditions.
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