Correlation Between Land Use Types And Heat Island Effect In Chengdu Based On Remote Sensing Data

With the development of China’s economy,the accelerating urbanization rate has led to the strengthening of the heat island effect.The urban heat island effect not only increases the ambient temperature,but also causes the accelerated consumption of energy,destroys the ecosystem and even endangers people’s health.The change of underlying surface in the process of urban construction is one of the main factors that cause the heat island effect.This paper will focus on the use of Landsat series data to study the inversion of land use types and surface temperature in 12 central urban areas of Pidu District,Wenjiang District,Jinjiang District,Qingyang District,Jinniu District,Wuhou District,Chenghua District,Xindu District,Shuangliu District,Longquanyi District,Qingbaijiang District and Xinjin District in Chengdu City in 2002,2006,2009 and 2018,and study the correlation between them.The cooling effects of different types and scales of urban parks on the surrounding environment were quantitatively analyzed.The main conclusions are as follows:（1）The land use types in the study area of Chengdu are mainly divided into cultivated land,construction land,woodland and water area,among which cultivated land accounts for the largest proportion.The change of land use types mainly reflects the dynamic changes between the impervious surface of construction land and cultivated land.The impervious surface area increased by 760.16 km²in 16 years,an increase of 243.69%.The arable land area decreased by 867.39 km²,or 27.05%;water area increased by 14.21km²,an increase of 26.46%;forest land area increased 8.66 km^2,by 7.82 per cent%.（2）In 2002,the heat island in the study area of Chengdu was mainly concentrated in the center of the urban area.In the later period,the area of the heat island gradually expanded and the influence range of the surrounding heat island effect expanded,but the thermal environment in the urban area was improved.The heat island effect in the southern region of Chengdu is more serious than that in the northern region;the proportion of heat island area in the eastern region is significantly higher than that in the western region.The average surface temperature of various land types in the study area is in the same order,which is construction land>cultivated land>forest land>water area.The high temperature area is mainly concentrated in construction land,and the low temperature area is mainly concentrated in vegetation land.（3）The relationship between land type change and surface temperature was quantitatively analyzed by NDVI and NDBI.The surface temperature in the study area decreased with the increase of NDVI index,and the surface temperature decreased by0.6°C-1.5°C when NDVI index increased by 0.1.On the contrary,the surface temperature increases with the increase of NDBI index.When the NDBI index increases by 0.1,the surface temperature increases by 1.45°C–3.38°C.The multiple linear regression results of the two and surface temperature show that the surface temperature will increase by 1°C–2.75°C for every 0.1 increase in NDBI index.When NDVI rises 0.1,it will produce 0.1°C-0.4°C cooling effect.（4）The cooling effect of urban parks and their area can be fitted to a logarithmic function.The increase of the cooling range will gradually decrease with the increase of the park area.The effective cooling distance of wetland parks is mainly in the range of 700 m from the vertical distance of the park boundary.The effective cooling distance of the comprehensive park is mainly within the range of 430 m with the vertical distance of the park boundary;the effective cooling distance of community parks is mainly within 270 m of the vertical distance of the park boundary.Due to the diminishing marginal benefit of the surrounding cooling effect,the wetland park area should not exceed 23 ha;comprehensive park should not exceed 16 ha;the community park area should not exceed 12 ha.