Evolution And Prediction Of Thermal Environment Pattern In Nanjing Based On CA-Markov Model

With the improvement of urbanization,the heat island effect is becoming more and more serious,it is harmful to the urban ecological environment and residents'health,and it is detrimental to the sustainable development of the city.Remote sensing data has become an important means for dynamic monitoring of heat island effect,relying on the advantages of high timeliness,wide coverage and easy acquisition.The long time series remote sensing data from2002 to 2017 of Landsat was used to analysis the spatial distribution characteristics and evolution trend of thermal environment in Nanjing based on RS and GIS.Then,the landscape pattern indexes were calculated toanalysis the evolution of landscape patternand its relationship with the thermal environment in Nanjing.The spatial distribution of thermal environment of Nanjing was simulated based on CA-Markov model,and the simulation accuracy was verified with the actual inversion result of land surface temperature.At last,the thermal environment of Nanjing in 2021 was predicted based on CA-Markov model.The main conclusions include:(1)From 2002 to2017,the area of high-temperature zone in Nanjing increased by453.10km~2and its proportion increased by 13.88%.The medium temperature zonedecreased by769.57 km~2 and its proportion decreased by 23.59%,which was the largest thermal grade.The heat island high temperature zone of Nanjing showed a trend of spreading from the main urban area to the surrounding urban area,and Jiangning,Qixia,Pukou and Yuhuatai has a fastergrowth than other districts.(2)From 2002 to 2017,the patch area of construction land increased by 444.83 km~2,and its degree of fragmentation andlandscape dominance increased.Blind expansion of construction land and pile-up of buildings would lead to a significant increase for surface temperature.The area of forest patches decreased by 133.72 km~2,and its degree of fragmentation and aggregation decreased.Continuous patches of forest land with high degree of aggregation could alleviate heat island effect.The landscape pattern index of water body fluctuated in a small range,but its change was not obvious.The surface temperature of the water body was the lowest,and the wide area of the water body has good cooling effect.The area of arable land patchesdecreased by 319.44 km~2,its fragmentation degree and landscape dominance decreased,and its shape became more complex.The arable land with crop cover could cause a certain cooling effect,but it was affected by seasonal change and crop harvest.(3)The CA-Markov model constructed in this study has certain reliability in simulating the distribution of thermal environment in Nanjing.The overall Kappa index of the simulation result was 81.79%,and the average error of each thermal grade was less than 3.76%.Based on the inversion result of land surface temperature in 2017,the thermal environment distribution of Nanjing in 2021 was predicted based on CA-Markov model,the result showed that the heat island effect in Nanjing would be further aggravated,andthe area of high temperature zone and sub-high temperature zone would respectivelyincrease by 45.19 km~2 and 137.14 km~2.In addition,the area of middle temperature zone,low temperature zone and sub-low temperature zone wouldbe decreased.