Research On The Mitigation Effect Of Green Space On Heat Island Effect In The Process Of Urbanization

This study selects the main urban area of Xi’an and the northern part of Chang’an District as the research area,and retrieves the surface temperature and urban green space information of the research area in 2000,2005,2010,2016,and 2022 based on Landsat data and Sentinel-2data.Using methods such as buffer zone analysis,landscape ecology and principal component regression analysis,the mitigation effects of urban green space on urban heat island effect at different scales and in different periods are discussed.The following main conclusions were obtained:(1)Since 2000,the urban heat island area in the main urban area of Xi’an has gradually increased over time.After reaching a peak of 474.31 km2 in 2016,the urban heat island area began to decline.From 2000 to 2022,the urban heat island in Xi’an showed a trend of shifting from the city center to its surroundings,from concentrated distribution to decentralized distribution;while the urban green space changed significantly in each research period,and the northern part of Chang’an District and Baqiao District in each administrative district The green area is the largest,and the green area of Xincheng District,Lianhu District and Beilin District is the smallest.(2)In the main urban area of Xi’an at different periods,except for very small patches and urban green patches with an area-to-perimeter ratio of APRA1,other urban green patches have obvious and stable cooling effects.From 2000 to 2022,with the passage of time,the cooling effect of urban green space of various types and APRA types in the main urban area of Xi’an has increased,and the enhancement speed of small green patches and APRA2 and APRA3 green patches quick.As the area of the green patch increases or the APRA increases(the shape tends to be regular),the cooling effect of the green patch continues to increase,but when the area of the green patch increases to a medium patch or the APRA increases to APRA3,as the area increases or The shape tends to be regular,and the rate of increase in the cooling rate becomes slower.(3)Under each research scale in 2010,2016 and 2022,the urban green space landscape pattern index in the main urban area of Xi’an is significantly correlated with the surface temperature,and remains relatively stable.As the research scale increases,the absolute value of the correlation coefficient between the green space landscape pattern index and the surface temperature increases,reaches a peak at the 7km×7km research scale,and then decreases with the increase of the research scale;The changing law of the adjusted R2 of the temperature principal component regression model is similar to the changing law of the absolute value of the correlation coefficient.When the research scale increases from 1km×1km to 7km×7km,the adjusted R2 keeps increasing and reaches the maximum at the research scale of 7km×7km.After that,it began to decrease.At the research scale of 7km×7km,the landscape pattern of urban green space can best explain the surface temperature.(4)In 2000 and 2005,the correlation between the urban green space landscape pattern and the surface temperature in the main urban area of Xi’an was low.By 2010,there was a significant correlation between the urban green space landscape pattern and the surface temperature.With the passage of time,the adjusted R2 value of the urban green space landscape pattern and the surface temperature regression model basically showed a trend of increasing significantly and then slightly decreasing at each research scale.The adjusted R2 reached its peak in 2016,which is consistent with the intensity of urban heat island.The change pattern is consistent.