Variation Of Land Surface Thermal Environment In Wenjiang District Based On The Landsat Images

With the rapid development of economy,the process of urbanization is speeding up.One of the most direct effects of urbanization on the natural environment is the change of land use/cover types.The difference of the thermodynamic properties of different land use/cover types leads to the change of the land surface thermal environment with the change of land use/cover types.The most typical thermal environment problem caused by urbanization is the heat island effect.At present,the heat island effect has been widespread concern in the community,it is also a hot field of scientific research.In this paper,the Landsat remote sensing images of three periods in 2004,2009 and 2015 in Wenjiang District were used as basic information,the land use/cover information and land surface temperature information in Wenjiang District was extracted respectively.According to the theory and method of landscape ecology,the landscape pattern index was used to quantitatively analyze the thermal landscape pattern and its change characteristics in Wenjiang District.At the same time,the land use/cover information and land surface temperature information are superimposed,then the relationship between land surface temperature and land use/cover can be studied,and some suggestions on improving land surface thermal environment in Wenjiang District are put forward.Specific conclusions are as follows:(1)From 2004 to 2015,the center of urban heat island gradually shifted from the old city to the industrial concentration area in the southwest of the city.The proportion of the three types of high-level thermal landscape showed an upward trend in Wenjiang District,reflecting the increasing severity of urban heat island effect in Wenjiang District.(2)In the class level,the dominance of the thermal landscape types of grade fifth and sixth increased,and the influence of the two thermal landscape types increased.Therefore the aggregation degree of the high grade heat island landscape increased,and patches of the high-grade thermal landscape showed a trend of clustering.(3)In the landscape level,the patch density and marginal density of thermal landscape in Wenjiang District declined year by year,so the fragmentation degree of thermal landscape decreased and edge morphology tended to simplicity;the aggregation degree increased year by year,so the distribution of similar patches tended to be compact at the landscape level;the diversity and evenness of thermal landscape were firstly increased and then decreased,and the diversity and heterogeneity of the thermal landscape showed an upward trend between 2004 and 2009,subsequently,the land surface thermal environment in Wenjiang District was gradually dominated by the dominant thermal landscape patches.(4)The water has a stable cooling effect,and the green space played a leading role in the low-level thermal landscape patches,so the reasonable allocation of water and green space can improve the land surface thermal environment.(5)There is a negative correlation between vegetation coverage and average land surface temperature,which can help to reduce the land surface temperature.To improve the land surface thermal environment of the built-up area by greening,on the one hand,we should increase the area of the urban green space,on the other hand,we should pay attention to the construction of the vegetation coverage per unit area of urban green space.