Research On SAR Image Monitoring Of Mountain Glaciers In Tibetan Plateau

Glaciers are natural products under specific climatic conditions.The physical characteristics of climate and water or ice determine the size of glaciers and their development and changes.Due to its high-altitude topography and cold climate conditions,the Qinghai-Tibet Plateau in my country has nurtured a large number of mountain glaciers,which play a very important role in the change of water resources in the west.As the global temperature continues to rise,global glaciers are facing severe threats.Mountain glaciers on the Qinghai-Tibet Plateau are also facing the same problem.Under the environment of rising global temperatures,about 80.8% of the glaciers in the Qinghai-Tibet Plateau are retreating,the huge glaciers near Mount Everest are undergoing drastic dynamic changes.This change not only seriously affects the supply of water resources for the people in the Qinghai-Tibet area,but also the steep terrain of the Qinghai-Tibet Plateau,and changes in glaciers are prone to natural geological disasters such as avalanches,landslides,and glacier lake outbursts,which seriously threaten the lives and properties of the people in Tibetan areas.Safety.Therefore,long term and effective monitoring of mountain glacier regions is extremely urgent.The Everest elevation measurement project in 2020 has become a milestone in the history of Everest surveying and has important significance in many aspects.Therefore,this article relies on the Mount Everest Glacier Change Monitoring sub-project of the Mount Everest elevation measurement project supported by the National Basic Surveying and Mapping Project.There are several representative glaciers in the Everest region of the Qinghai-Tibet Plateau.Through monitoring and research on the changes of glaciers in the region,it accurately reflects the changes in the velocity of glaciers in the Everest region and the development and changes of surface deformation.For the main topography in the Everest region.A clearer and more comprehensive understanding of the change of ground features,and an objective recognition of the serious threat of climate change to glacier changes,has important practical significance in enabling mankind to cope with global climate change,ecological environmental protection and natural disaster prevention.The research results and innovations are as follows:(1)Glacier flow velocity is an important feature of glacier dynamic changes,and effective monitoring of glacier flow velocity is conducive to timely and accurate inversion of the laws of glacier development.Among them,offset tracking technology is one of the mainstream technical methods for glacier flow velocity analysis.This paper use the offset tracking method to study the ALOS PALSAR-2 image data of typical mountain glaciers such as Kangxiong Glacier and Kazhenpu Glacier in the Mount Everest region,and extracted two glaciers in 2015-2016,2016-2017,2017-2018 and Glacier velocity distribution information for a total of 4 stages in 2019.This article takes into account the joint effect of the elevation and slope of the glacier area on the glacier velocity,introduces a spatial three-dimensional surface model,transfers the planar single-factor analysis to the spatial multidimensional analysis,and finds the slope-elevation-glacial velocity by constructing a quadric surface model the relationship between changes.It is found that in the glacier velocity-slope-elevation model with glacier velocity as the dependent variable,the quadratic coefficients of the quadratic term of elevation,the quadratic term of slope,and the mixed quadratic coefficient of elevation and slope are all much smaller than the coefficient of the first term.A linear relationship;the first-order coefficients of elevation H are all positive,the greater the elevation,the faster the flow velocity,which is positively correlated.(2)In this paper,SBAS technology is applied to mountain glacier distribution areas to explore the influence of regional surface deformation on mountain glacier morphology changes.The Mw7.8 earthquake occurred in Nepal at 14:11 on April 25,2015,making the impact of the earthquake on mountain glaciers in the Qinghai-Tibet Plateau a research hotspot.In this paper,based on 24 scenes of ALOS PALSAR-2 data,the average subsidence rate map of the survey area is obtained by using the small baseline aggregated aperture radar interferometry technology.Baseline constraints and differential calculations eliminate or weaken the phase residuals caused by surface fluctuations,the phase residuals caused by atmospheric delays,and the phase residuals caused by other noises,so as to obtain a more reliable sedimentation rate map.In order to further determine the relationship between glacier changes and earthquakes,this paper normalizes the deformation and the contribution of the deformation,and monitors the glacier flow velocity before,during and after the earthquake on the glaciers affected by the Nepal earthquake.Surface deformation and velocity changes jointly analyze the impact of the Nepal earthquake on the glaciers in the study area.The following conclusions are obtained:(1)The closer to the seismic source,the greater the impact,and the more severe the surface deformation.As time changes,the deformations show a gradual decrease,and the surface changes tend to stabilize.(2)The earthquake broke the laws of natural terrain subsidence,leading to small-scale uplifts in parts of the study area in the year of the earthquake or several years after the earthquake,as well as the affected areas.With changes in natural terrain,the movement of glaciers at the epicenter and for a period of time after the earthquake has been accelerating.