Spatio-temporal evolution of thermal environment in Tianjin City and its influencing factors
Background,aim,and scope Since the Beijing-Tianjin-Hebei coordinated development plan was promoted as a national strategy in 2014,the economic system of Tianjin City has been continuously improved.Currently,Tianjin City has been promoted to a super-city,the urbanization process has entered a new development stage,and the urban thermal environment has also undergone significant changes.To understand the influence of the urban heat island effect on the city,it is vital to investigate the spatio-temporal changes of the urban heat island effect in Tianjin City,analyze the influencing factors,and give reasonable suggestions.Materials and methods To investigate the current potential effect of data and deeply study the change law and influencing factors of heat island in the central urban area of Tianjin City in recent years,this paper collected Landsat remote sensing image data from 2005 to 2020,conducted land surface temperature inversion,and calculated the urban heat island proportion index of 10 main urban areas of Tianjin City by employing the radiative transfer equation method.The annual variation of the urban thermal field was demonstrated using the standard deviation ellipse method,and the local key areas of temperature anomaly were determined.Then,the response relationship between land cover type and land surface temperature was investigated through land surface temperature and land use classification.Finally,the geographical detector was employed to investigate the influence and interpretation degree of elevation,green space,built-up land,and water body on heat island change.Results From 2005 to 2020,the heat island footprint of downtown Tianjin developed from six districts to four suburban districts along the main road.The urban heat island ratio index increased from 0.23 in 2005 to 0.30 in 2014 and then decreased to 0.27 in 2020.Meanwhile,from 2005 to 2020,the main axis of urban heat island development was in the direction of northeast to southeast,and the deflection angle ranged from 118.97° to 129.80°.Also,both the proportion of built-up land in the central urban area and the proportion of water bodies in Tianjin City are increasing year by year.The average temperature of various types of land objects is ranked as built-up land＞green space＞water body.The results of geographic detector analysis suggest that NDBI and NDVI are the main factors affecting land surface temperature change,and NDVI and MNDWI are the strongest combinations of factors driving the urban thermal environment.Discussion The urban thermal environment in the central urban area of Tianjin exhibits a trend of first increasing and then decreasing,and the distribution direction of the heat island is obvious and gradually develops from a single-center structure to a multi-center structure.The surface temperature is jointly affected by many factors,and the comprehensive influence of two factors is greater than that of a single factor.The research indicates that the remote sensing indices NDBI and NDVI,which are closely related to urban construction and human activities,significantly affect the spatial distribution of surface temperature.This is because the built-up land has a large heat capacity,while the vegetation reduces the surface heat capacity due to its transpiration and the shielding of the surface,making the spatial differentiation of surface temperature crucial.As important components of the urban ecosystem,urban green space and water bodies play an important role in regulating the urban heat island effect.Then,the cooling efficiency of the two components in the heat island effect was quantitatively analyzed.Conclusions The heat island effect in Tianjin City exhibited a trend of increasing first and then decreasing.The urban heat island proportion index reached its highest value in 2014 and decreased again in 2020.The regional spatial distribution of the heat island radiates outward,and the four districts around the city are undergoing rapid urbanization,which is a key factor for the change in urban heat island spatial patterns.The results obtained by the geographic detector suggest that vegetation and water have the most significant mitigation effect on Tianjin's urban heat island.Recommendations and perspectives In future urban construction,the layout and planning of urban green space and water bodies should be strengthened,and the landscape pattern of blue-green space should be optimized to mitigate the influence of the urban heat island effect.
land surface temperatureLandsaturban heat islandradiative transfer equation methodgeographic detector
万方数据
维普
