锡林郭勒典型草原区积雪过程与风雪流研究
发布时间：2018-11-17 17:54
【摘要】：锡林郭勒草原是温带草原最为典型的代表,是我国重要的牧业生产基地,同时也是我国北疆重要的生态屏障。研究区地处我国三大积雪高值区之一,积雪资源丰富,是重要的季节性积雪区。漫长严寒的冬季,加上强劲的风力条件,积雪灾害频发,严重阻碍了地区经济的发展。本文在对典型草原地区风雪环境气象因子动态分析和积雪时间尺度分析基础上,通过对积雪过程及风雪流的野外观测,分析了不同时期积雪的密实化过程,不同环境及积雪条件下的风雪流运行情况,以及风雪流二次积雪分布规律,主要研究结果如下:1.锡林浩特45a降雪量和积雪日数没有明显的突变点,而积雪深度在2000年和2003年发生了两次有少到多的突变;降雪量、积雪日数和积雪深度三个积雪因子的主周期均为11a;降雪量、湿度、蒸发量和风速对吹雪的发生日数影响较大,通过BP神经网络模型的预测,吹雪发生日数呈减少趋势。2.稳定积雪期内,依据具有显著阶段变化特征的积雪深度对积雪密实化过程划分,可分为积雪密实化剧烈变化期(前24h)、快速变化期(24h—48h)和稳步发展期(48h之后)三个阶段;不稳定积雪期内,积雪深度与积雪密度均没有明显的分段变化特征,且整个密实化过程明显快于稳定积雪期。积雪密度随沉积时间逐渐增大。3.大针茅平坦草地在多风速梯度作用下,近地表100cm范围风雪流表现为移雪强度、移雪量百分比均随距离雪面高度增加而急剧减弱。随着2m处风速的增加,相同高度处移雪强度增强,风雪流结构函数发生从对数函数到幂函数的转变。移雪量主要集中在近地表20cm范围内,占到总移雪量的80%以上;平均移雪强度与2m高度处风速呈极显著(P0.001)的幂函数关系,关系式为Q=a·Vb形式,幂指数约为5,随风速增加平均移雪强度发生从缓慢增加到急剧增强的变化过程。4.积雪面出露的植被、积雪沉积时间、积雪深度、地形条件等环境或积雪本身均对风雪流的运行存在不同程度的影响。移雪强度、单宽输雪率等指标随着出露植被高度、出露植被盖度的增加而显著减弱,积雪沉积越久形成风雪流强度越弱;由于地形对风速廓线的影响,迎风侧的风雪流运行的高度和强度明显强于背风坡,在坡中位置表现的最为显著。5.大针茅平坦草地积雪深度随植被高度呈线性关系增长,相关性强弱表现为放牧打草封育。积雪深度随植被盖度呈对数函数增加,当植被盖度增加到一定程度后积雪深度增加趋于缓慢;大针茅平坦草地内积雪深度在降雪量丰富年份沉积的更多,而且在利用程度轻的草地内表现的更加明显。
[Abstract]:Xilingol prairie is the most typical representative of temperate grassland, an important animal husbandry production base in China, and also an important ecological barrier in northern Xinjiang. The study area is located in one of the three high value snow cover areas in China, which is rich in snow resources and is an important seasonal snow cover area. The long cold winter and the strong wind condition, the frequent snow disaster seriously hindered the development of the regional economy. Based on the dynamic analysis of snow and snow environmental meteorological factors and the analysis of snow cover time scale in typical grassland area, this paper analyzes the snow densification process in different periods through the field observation of snow cover process and snowstorm flow. The operation of snow flow and the distribution of secondary snow cover under different environment and snow cover conditions. The main results are as follows: 1. In Xilinhaote, there were no significant abrupt changes in snow amount and snow days in 45a, but there were two abrupt changes in snow depth in 2000 and 2003. The main periods of snow fall, snow days and snow depth were 11a. Snowfall, humidity, evaporation and wind speed have great influence on the number of snow blowing days, and the number of snow blowing days is decreasing through the prediction of BP neural network model. 2. In the stable snow cover period, the snow compaction process can be divided into two periods according to the snow depth, which has the characteristic of significant phase change, which can be divided into two periods (the first 24 hours). Rapid change period (24h-48h) and steady development stage (after 48 hours); During the unstable snow cover period, the snow depth and the snow density have no obvious variation characteristics, and the whole compaction process is obviously faster than that of the stable snow cover period. The density of snow increased with the deposition time. Under the action of multiple wind speed gradient, the snowdrift intensity in the 100cm range near the surface was observed, and the percentage of snow moving decreased sharply with the increase of the height of snow surface. With the increase of wind speed at 2m, the intensity of snow moving at the same height increases, and the structural function of snow flow changes from logarithmic function to power function. The amount of snow moving is mainly concentrated in the range of 20cm near the surface, accounting for more than 80% of the total amount of snow moving. The relationship between the average snow moving intensity and the wind speed at 2m height is very significant (P0. 001). The relation is Qa Vb form, and the power exponent is about 5. With the increase of the wind speed, the average snow moving intensity changes from slow to sharp. 4. The vegetation, deposition time, snow depth, topographic conditions and snow cover have different effects on the flow of snow. The intensity of snow movement and the rate of single wide snow transport decreased with the height of exposed vegetation and the coverage of exposed vegetation. The longer the snow deposited, the weaker the snowstorm flow intensity was. Because of the influence of topography on the wind profile, the height and intensity of the windward wind flow is obviously stronger than that of the leeward slope, and the position in the slope is the most obvious. The depth of snow cover increased linearly with the height of vegetation, and the correlation was shown as grazing and forage fencing. The snow cover depth increases with the vegetation coverage as a logarithmic function, and when the vegetation coverage increases to a certain extent, the snow cover depth increases slowly. The depth of snow in the flat grassland is more than that in the year of rich snowfall, and it is more obvious in the grassland with light utilization.
【学位授予单位】：内蒙古农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S812
本文编号：2338623
[Abstract]:Xilingol prairie is the most typical representative of temperate grassland, an important animal husbandry production base in China, and also an important ecological barrier in northern Xinjiang. The study area is located in one of the three high value snow cover areas in China, which is rich in snow resources and is an important seasonal snow cover area. The long cold winter and the strong wind condition, the frequent snow disaster seriously hindered the development of the regional economy. Based on the dynamic analysis of snow and snow environmental meteorological factors and the analysis of snow cover time scale in typical grassland area, this paper analyzes the snow densification process in different periods through the field observation of snow cover process and snowstorm flow. The operation of snow flow and the distribution of secondary snow cover under different environment and snow cover conditions. The main results are as follows: 1. In Xilinhaote, there were no significant abrupt changes in snow amount and snow days in 45a, but there were two abrupt changes in snow depth in 2000 and 2003. The main periods of snow fall, snow days and snow depth were 11a. Snowfall, humidity, evaporation and wind speed have great influence on the number of snow blowing days, and the number of snow blowing days is decreasing through the prediction of BP neural network model. 2. In the stable snow cover period, the snow compaction process can be divided into two periods according to the snow depth, which has the characteristic of significant phase change, which can be divided into two periods (the first 24 hours). Rapid change period (24h-48h) and steady development stage (after 48 hours); During the unstable snow cover period, the snow depth and the snow density have no obvious variation characteristics, and the whole compaction process is obviously faster than that of the stable snow cover period. The density of snow increased with the deposition time. Under the action of multiple wind speed gradient, the snowdrift intensity in the 100cm range near the surface was observed, and the percentage of snow moving decreased sharply with the increase of the height of snow surface. With the increase of wind speed at 2m, the intensity of snow moving at the same height increases, and the structural function of snow flow changes from logarithmic function to power function. The amount of snow moving is mainly concentrated in the range of 20cm near the surface, accounting for more than 80% of the total amount of snow moving. The relationship between the average snow moving intensity and the wind speed at 2m height is very significant (P0. 001). The relation is Qa Vb form, and the power exponent is about 5. With the increase of the wind speed, the average snow moving intensity changes from slow to sharp. 4. The vegetation, deposition time, snow depth, topographic conditions and snow cover have different effects on the flow of snow. The intensity of snow movement and the rate of single wide snow transport decreased with the height of exposed vegetation and the coverage of exposed vegetation. The longer the snow deposited, the weaker the snowstorm flow intensity was. Because of the influence of topography on the wind profile, the height and intensity of the windward wind flow is obviously stronger than that of the leeward slope, and the position in the slope is the most obvious. The depth of snow cover increased linearly with the height of vegetation, and the correlation was shown as grazing and forage fencing. The snow cover depth increases with the vegetation coverage as a logarithmic function, and when the vegetation coverage increases to a certain extent, the snow cover depth increases slowly. The depth of snow in the flat grassland is more than that in the year of rich snowfall, and it is more obvious in the grassland with light utilization.
【学位授予单位】：内蒙古农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S812
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