Research Of Land Use Planning Strategy Based On Urban Thermal Environment Assessment

With the rapid development of modern cities,the urban functional and constructive area is expanded continuously and urban land utilization is constantly transformed.Skyscraper not only promotes economic development but also results in ecological and environmental pressure.Urban thermal environment has attracted more attention from urban planning and ecological protection scholarships after urban heat island effect was proposed.Up to now,urban thermal environment has been a critical issue of constructing comfortable and liveable city.Xi'an,the start of silk road,always expands its urban construction land under the promotion of western development and the integration of Xi'an and Xianyang,resulting in prominent thermal environment.The paper started with data from Landsat 5 TM on July 17,1992 and July 24,2006 and data from Landsat 8 OLI/TIRS on May 25,2019.Applying mono-window algorithm and with the aid of Arc GIS 10.2?ENVI 5.2 and Frangstas 3.3,the author firstly analyzed the time and space and thermal landscape pattern change of the thermal environment in the main urban area of Xi'an and change range,space conversion of different land-use types,as well as evaluated heat effect of different land-use types in the main urban area of Xi'an.Secondly,based on the above evaluation result and determining 2 kilometers on both sides of Ba River as research zone,the author divided the zone into 200*200-meter grid and buffer area with 100-meter spacing and analyzed the quantitative relationship of land-use types on both sides of Ba River and thermal environment under vertical(time)and horizontal(buffer)changes.Finally,the author proposed land-use planning strategy from vertical system(theory)and horizontal system(practice)based on above analysis results.The paper focused on the main urban area of Xi'an.The author sorted out literature of thermal environment research content and evaluation methods,evaluated thermal environment by thermal infrared remote sensing monitoring and assessed the heat effect of different land-use types of Xi'an in a macroscopic view combining with the third-phase retrieval and interpretation results of land surface temperature from remote sensing images in Xi'an.The evaluation results showed:(1)Thermal environment of Xi'an and land-use types and setup had changed a lot,especially in Ba Bridget District and Weiyang District.The land surface temperature of Xi'an increased greatly and had inter-annual variability,heat island was sharply expanded to the suburb in a sporadic or flaky way and the overall thermal landscape pattern had changed significantly and the plaque was gradually distributed evenly.The construction land was transferred overall,replacing grassland to be the main land-use type of the main urban area of Xi'an.(2)The average temperature of construction land in main urban area of Xi'an was the highest from 1992 to 2019 and that of water area was lowest,and the land surface temperature of every land-use type rose with time.The normalized building index(NDBI)was positively correlated with surface temperature,while Normalized Vegetation Index(NDVI)and Normalized Water Index(NDWI)were negatively correlated with surface temperature,that was to say that urban construction land was positive to urban heating up,while plant and water were negative to urban heating up.Based on comprehensive evaluation analysis on thermal environment of Xi'an,the author analyzed the vertical and horizontal quantitative relationship of the proportion of land-use area on both sides of the Ba River and the surface temperature from a mesoscopic perspective.The results showed:(1)In 2019,construction,water,forest and grass influenced temperature of both sides of Ba River the most.The grassland,arable land,water area and woodland on the east of the Ba River were negatively correlated with surface temperature(cooling land),and the cooling effect was water area,woodland,grassland and arable land in turn.Water area and woodland on the west of Ba River had a better cooling effect than the est of of Ba River,while grassland on the east of Ba River had a better cooling effect than the west of Ba River.(2)In 2019,there would be a better cooling effect when the proportion of water area,grassland,woodland and arable land on the east of Ba River was 3.9 percent,13.1 percent,18.7 percent and 11.6 percent respectively,while there would be a better cooling effect when the proportion of water area,woodland and grassland on the west of Ba River was 0.81 percent,14.0 percent and 11.6 percent respectively.Finally,the quantitative analysis results of land-use types and land surface temperature on both sides of Ba River in 2019 was applied in city planning to construct vertical and horizontal land-use optimization ideas for improving thermal environment of research zone.Based on Xi'an Land Use Master Plan(2006-2020),the author proposed land-use optimization strategy of improving overall thermal environment of research zone theoretically.Then in the light of research zone heat island and land use situation,the heating of research zone could be restricted by introducing water and green land and other cooling lands,controlling high temperature in the core area of heat island,dispersing gathering areas in heat island and adjusting green island area.