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Study On Hydro-thermal Condition And Snow Cover Characteristics Of Frozen Soil In Thawing Period

Posted on:2019-03-18Degree:MasterType:Thesis
Country:ChinaCandidate:B B DuanFull Text:PDF
GTID:2370330566466877Subject:Science
Abstract/Summary:PDF Full Text Request
In seasonally frozen soils and snow-covered areas,due to the different nature of underlying surfaces,the time and rate of freezing and thawing of frozen soils and the melting of snow melting are very different,and the analysis of snow-melting seasons under forested land,inter-forest grassland,and grassland The change of surface humidity is important for optimizing the input of soil moisture parameterization scheme in simulated snowmelt runoff in arid regions,simulating the snowmelt flood formation process,and improving the accuracy of flood forecasting;the study of snow cover characteristics is important for research on snow water resources and disasters.On the other hand,the study of the characteristics of snow cover can provide references for the investigation of snow distribution and the study of snow cover disasters.In this paper,the Tianshan mountainous area is located in the area around the lake.The data of temperature,temperature and humidity,and snow characteristics are obtained based on automatic field observations and artificial measurements.The two parts are analyzed and studied: First,different phases of the snowmelt period(The comparison of water(wet)heat(temperature)in seasonally frozen soils with different underlying surfaces;the second is to analyze and discuss the variation of snow cover characteristics in different phases of snow melting period.The results show:(1)The overall change trend of the frozen soil moisture in all layers during the snowmelt period has experienced three phases: rise-fall-stabilization;the frozen soil temperature is affected by changes in temperature and snow cover,showing a rapid rise-slow decline-a change in near-uniform rise;(2)The freezing depth of frozen soil has a significant relationship with altitude:the higher the altitude,the greater the depth of frozen soil,the melting time of frozen soil is closely related to the altitude;the change of frozen soil thickness is a process that increases first and then decreases.The soil melting process is more devious and shows two-way melting,so the freezing-thawing rate of frozen soil is unevenlydistributed throughout the soil freezing period;(3)Characteristics of soil temperature and humidity changes on different underlying surfaces during the snow melting period: The temperature of permafrost on the underlying surface of the Aimin Bridge grassland increases rapidly during the initial period of the snowmelt.The characteristics of the soil temperature during the fluctuation period are: the soil temperature goes down from the surface.The higher the time,the more stable it is.During the fluctuation period,the curve of soil temperature in each layer of grassland in Donggou forest was similar to the U type,and the soil temperature decreased from the surface layer to the lower layer;during the stable period of snow melting,the temperature gradient of the vertical soil depth direction pointed to the surface.In the initial period of snowmelt,the lower the soil temperature is,the lower the soil temperature is from the surface,the fluctuation period and the stabilization period,the soil temperature in each layer is very stable,which is very different from the underlying surface of the grassland and the underlying surface of the forest grassland;(4)The correlation between temperature and soil temperature and humidity of different underlying surfaces: the surface area of grassland,the influence of temperature on the temperature of shallow soil is higher than that of deeper soil;the air temperature and shallow surface of grassland under the forest is 5cm,10 cm,The correlation of soil temperature at 20 cm reached a significant level,and the correlation between ground surface air temperature and soil temperature did not reach a significant level.The correlation between air temperature on the underlying surface and soil moisture did not reach a significant level;soil temperature had a greater influence on soil moisture than temperature;(5)The hydrothermal relationship of the same soil depth for different underlying surfaces: the soil moisture content in the 5 cm section of the same underlying surface,the farther the distance from the same profile,the weaker the correlation,the different performance of the forest land;The correlation between soil water content of 20 cm section and the soil temperature in each section shows that the correlation between soil moisture content and the soil temperature of each section is stronger than that ofgrassland.,and with the increase of the depth of the soil profile correlation.Compared with the three kinds of underlying surfaces,the correlation between the soil moisture content and the soil temperature in the 40 cm section of the inter-forest grassland under the forest is significantly stronger than that of the grass surface and the underlying surface of the forest;(6)The temperature variation trend of the yin and yang slope of the main test site is generally consistent with that of the snow layer.The temperature of the snow layer on the sunny slope is higher than the shady slope of the same profile layer;the average moisture content of the snow layer on the sunny slope is higher than the shady slope;In terms of observation period,the density of the bottom layer is increasing,and the upper layer and the middle layer are slightly decreased.In the period of snow melting,due to snow melting,the water content and density of the snow layer also change day and night.In general,the depth of snow depth showed a decreasing trend,and the initial depth of snow cover on sunny slopes was less than that of the shady slopes,but the snow ablation rate of sunny slopes was significantly faster than that of the shady slopes;(7)The snow temperature in Yinyang slope has a strong correlation with air temperature,and negatively correlates with the changes in water content of snow layer.The change of snow layer density is synchronous with the change of snow temperature;the moisture content of sun slop is negatively correlated with snow temperature.The snow slope densities on the slopes have poor correlation with the above factors;the snow slope densities on the sunny slopes are highly correlated with the snow layer temperature and the snow layer moisture content;the snow depth is positively correlated with the air temperature,and the snow cover temperature is expressed as Negatively related.
Keywords/Search Tags:Snowmelting period, Seasonal frozen soil, Underlying surface, emperature and humidity, Snow characteristics
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