Research on the evolution law of permafrost under the influence of urbanization based on remote sensing technology

The permafrost of Mohe County and its suburbs in the Daxing’an Mountains has been influenced by the urbanization. Remote sensing, GIS technology and numerical simulation was used to study the temperature variations of permafrost with the changes in surface vegetation that cover Mohe County and suburban areas, and the law of permafrost degradation on the study area was analyzed. The research results show that the urban area of the study area increased 114.42% from 2000 to 2016, and the urbanization process is continuing to accelerate. The Normalized Difference Vegetation Index map of 2017 in Mohe County and its suburbs was studied and the maximum proportion of vegetation coverage was different in the four seasons. The numerical calculation model results show that the permafrost temperature change in the study area cyclically fluctuates in a cosine form. The annual variation curve of permafrost temperature gradually decreased and its accompanying phase lag increased with depth. The annual temperature change value with the different depths of the town was greater than the natural ground. The maximum permafrost thawing depths of the town and natural ground were 4.2 m and 2.82 m in 50 a, and the degradation rates of the two permafrost are, respectively, 0.88 cm/a and 0.46 cm/a. These results show that urbanization has accelerated the degradation of permafrost.