A Study On Simulation Of The Permafrost Distribution In Qinghai-Tibet Plateau Based On RS/GIS

As an important part of cryosphere,frozen soil covers a large area of global land surface.And permafrost covers about 24%of the northern hemisphere.For its wide distribution and unique thermal characteristics of water,frozen soil is a very important factor of land surface process.Permafrost mainly distributed in Qinghai-Tibet Plateau,Pamirs Plateau, Daxinganling and the top of some eastern mountains in China.And the permafrost mainly in Qinghai-Tibet Plateau at high altitude is the world's highest elevation and largest area of permafrost regions in the lower latitude.A clear understanding of the the laws of permafrost distribution in Qinghai-Tibet Plateau,which is not only conducive to better plan and resolve the actual engineering problems of permafrost regions,but also it will have a far-reaching significance for the study of permafrost changes,the regulation and contribution to regional water resources in Qinghai-Tibet under climate warming.For the vast area,the measured data of frozen soil is relatively few in Qinghai-Tibet Plateau.In the western,the stations and data is not available,which makes restrict to the traditional method rely on observational data.The existence of frozen soil is bound to their surrounding environment for its wide range and unique thermal characteristics of water,and reflects on the ground information.However we can rapidly obtained a large area and multi-temporal ground information related to permafrost using RS,which makes it possible to study permafrost from the view of RS.Based on GIS technology,using RS data as the main data sources and combined with the feature of permafrost distribution in Qinghai-Tibet Plateau,we build two models:Retrieval Model of Ground Temperature based on RS/GIS and Multi-variable Comprehensive Analysis Model.The Retrieval Model of Ground Temperature based on RS/GIS is on the foundation of MAGT,which is the key division indicator of permafrost in Qinghai-Tibet Plateau.Through the relations established between MAGT and RS information to obtain the MAGT indirectly,and achieved the purpose of permafrost division.While Multi-variable Comprehensive Analysis Model depends entirely on the ground data related to the permafrost distribution to instruct the occurrence of permafrost.Considering the permafrost map used to verify the simulation results,which is based on the measured ground temperature along the Qinghai-Tibet road,so the status of permafrost distribution in the permafrost map should be more reliable along the Qinghai-Tibet road.Therefore we choose the scope along Qinghai-Tibet road as a test area to simulate the status of permafrost distribution using the established model, compared and analyzed the simulation results with the part of permafrost map along the Qinghai-Tibet road.On the premise of simulation results in a very good response to the permafrost distribution,extended the model to the Qinghai-Tibet Plateau.In order to study the merits and demerits of various models,and evaluate the simulation results,we selected the Elevation Model and Frost Number Model to simulate the permafrost distribution along the Qinghai-Tibet road.Compared and analyzed the results with the simulation results of the two models created in this article.Obtained the following conclusion:1.The frozen soil is divided based on the Retrieval Model of Ground Temperature based on RS/GIS,through setting up the relationship between MAGT and remote sensing variables,indirectly obtaining MAGT.The model precision depends on the quantity of the ground temperature observation points and distribution situation.The quality of regression equation is not ideal,because the ground temperature observation points used to set up model are small distribution in island permafrost zone.There are a certain differences between the simulation results in south island permafrost zone and the frozen soil distribution image.The simulation precision will be improved by increasing the ground temperature observation points' quantity in the island permafrost zone.If the quantity of the ground temperature observation points is enough,this method is still a feasible one which used to obtain the permafrost distribution.2.Multi-variable Comprehensive Analysis Model uses the statistical relationship of surface in permafrost zone variables to indirectly infer the existence of permafrost. The sample points are representative.Because they were picked up along the road, and there were some points distributed on the island permafrost zone.Contrasted with DEM Model,Frost Number Model,Multi-variable Comprehensive Analysis Model shows the frozen soil distribution along the Qinghai-Tibet highway well.Using this model,the relative error of simulation area is less,the firing between the result and frozen soil distribution is best.3.The Multi-variable Comprehensive Analysis Model is used in the whole Qinghai-Tibet Plateau in order to simulate the distribution of frozen soil.The simulation result basically shows the frozen soil distribution principle.The area of permafrost is 136.33 million square kilometers,and that is 52.7 percentage of the whole Qinghai-Tibetan Pateau area.4.In the process of setting up the ground temperature model based on RS and GIS, the stability and prediction ability of model improved obviously,segmented considering the equivalent latitude.The determination coefficient R~2 is improved from 0.598 to 0.617 and 0.826.It shows that slope and aspect have important effect on the frozen soil distribution in Qinghai-Tibeta Plateau.5.In the process of calculating the frost-number model,considering the hardly obtaining of ground temperature by traditional method,affected by the interpolation precision,the precision of simulation result is influenced.Improving the model by trying to use ground temperature,the simulation result is not very well.Therefore,the attempt of introducing the ground temperature retrieval from RS in Fost Number Model is not successful.6.High resolution ASTER data are used in frozen soil simulation in partial area along the road.The result shows that,the precision of simulation result is improved. Especially,in the island permafrost zone,contrasted with the MODIS data simulation result,ASTER data simulation result has the better fitting with frozen soil distribution image.Compared with previous studies,special features of this paper are as follows:1.Based on GIS,and taken the remote sensing data as the main data source,we established the permafrost model suitable for Qinghai-Tibet Plateau,and simulated the distribution of permafrost in Qinghai-Tibet Plateau,which realized the application of remote sensing technology in the study of permafrost distribution in Qinghai-Tihet Plateau.2.Extracted the environment information related to permafrost distribution,such as elevation,land surface temperature,vegetation,soil moisture and so on,which make up for the lack of permafrost data in Qinghai-Tibet Plateau.Compared with the previous studies that only considered a single factor of elevation or air temperature, the model established in this paper is more reasonable.3.Unfrozen regions reflected in the simulation results for the first time,and the simulation results are better fit to the actual distribution of permafrost.Mapping permafrost based on remote sensing technologies is a meaningful work.It is a meaningful attempt to study the simulation of permafrost distribution from the view of RS.