Temporal And Spatial Variation Of The Imperious Surface Area In Zhengzhou City And Its Relationship With Thermal Environment

Urban heat island can increase the city's energy consumption,reduce air quality,and even endanger public health.In the process of urbanization,along with the expansion of the city,the impervious surface of the city also increases,and the research of the urban thermal environment is gradually concerned.The analysis of the characteristics of urban impervious surface expansion and its impact on urban thermal environment is of great significance to alleviate and improve the ecological environment of urban heat island effect.Landsat imagines acquired on August 27,2000,August 24,2004,August 25,2008 and July 28,2015 and meteorological data in Zhengzhou were selected to do as the study data,By using GIS and RS as techniques,the main research contents are as follows:(1)To derive impervious surface area in the study area.Calculating the change,expansion rate and expansion intensity of the impervious surface area in Zhengzhou to analyse spatial and temporal changes of impervious surface area;in the space,Using gravity transfer method and quadrant azimuth analysis method to analysis impervious surface area.(2)Using the satellite thermal infrared images and meteorological data of the transit time,Using Xu Hanqiu's single window algorithm to derive normalized difference land surface temperature of the study area,then to obtain the city heat island ratio index;using the D-value method to obtain 2000-2004,2004-2008 and 2008-2015 the normalized difference land surface temperature image and divided them into 5 levels to analyse the temporal and spatial variation of the study area heat condition.(3)Using statistical methods and ArcGIS10.2 statistical tools to make regression analysis between the impervious surface area and normalized land surface temperature.(4)Using difference calculation method to obtain the 2000-2004,2004-2008 and 2008-2015 impervious surface area difference image,then extract the average impervious surface area value of five levels of thermal conditions change and Analysis of the influence of impervious surface area expansion on urban thermal environment.The results show that:(1)the impervious surface area in Zhengzhou is in a state of high-speed expansion from 2000 to 2015,but it shows different direction and intensity in different periods.Since 2000,with the expansion of the city,the impervious surface area of the study area increased from 158.71km~2 in 2000 to 367.70km~2 in 2015,the average expansion rate per year is 13.93km~2,the impervious surface area of the study area expended at a high-speed.spatial expansion direction and strength of the impervious surface area are not the same in different time.from 2000 to 2004,the western and southwest direction of the impervious surface area has a high expansion speed;from 2004 to 2008,the impervious surface area of the study area reflect balanced expansion,the expansion speed and strength of the different directional impervious surface area is not much different,but higher than the previous stage;from 2008 to 2015,expansion speed and intensity of east and southeast direction were significantly higher than other directions.On the whole,northern and eastern expansion area of the impervious surface area of the study area is higher than the southern and western,using gravity transfer method we can see that from2000,the focus of Zhengzhou city development transfer to the north and east,the major construction direction of the study area is in eastern and Northern regions.(2)Urban thermal conditions showed a trend of deterioration on the wholeHigher temperatures and urban heat island centralized in the urbanized area,Longhu lake,Longzi Lake,Ruyi lake,Chang Zhuang reservoir,Xiliu Lake and the green land producing'cold island'and'cool corridor'.During the four period,the value of Urban-Heat-Island Ratio Index increased gradually,and the area of urban thermal deterioration is more than the area of improvement.(3)there is a positive correlation between impervious surface area and land surface temperature, which can reflect the heterogeneity of thermal field.The covariance of four periods are greater than 0,indicating that both have positive correlation; land surface temperature spatial variation could be well explained by impervious surface area value with their regression coefficient ranging from 0.973 to 0.989;NDLST increased by 0.026-0.035 respectively when ISA value increased by 0.1.the impervious surface area has a positive role in promoting the land surface temperature and the urban heat island enhancement.(4)the change of urban thermal condition is obviously affected by urban constructionThermal variation showed adeteriorating trend from lower ISA value areas to higher ones.The ISA difference between the thermal improvement area is negative.the green land and water bodies can adjust the thermal environment,reduce the influence of heat island.The ISA difference between the thermal deterioration area is positive Urban expansion was regarded as a powerful driving force in thermal deterioration and UHI effect aggravation.