Temporal And Spatial Variations And Correlation Analysis Of Urban Heat Island And Key Atmospheric Particles In Tianjin

With the acceleration of the urbanization and industrialization of China's economic development,the urban heat island effect and urban air pollution problems have become more and more serious,and the influence of human factors on urban climate and air quality has become more apparent.Based on MODIS surface temperature product data,this paper extracts the urban thermal degree spatial pattern of different time phases in Tianjin,and statistically compares different thermal level landscape indices from three aspects:quantitative characteristics,morphological characteristics and structural features,analyzes their temporal and spatial pattern characteristics,calculates different thermal levels,and reveals its temporal and spatial variation using transfer matrix.Based on the geographically weighted regression model,using the national conditions monitoring data,environmental monitoring data and pollution enterprise data utilization correlation analysis,the best subset regression of PM2.5 and PM10 modeling factors on the screen is obtained,and three stages(2013,2015 and 2017)of temporal and spatial distribution and variation characteristics of PM2.5 and PM10 in Tianjin are obtained.Finally,the correlation between other influencing factors including PM2.5 and PM10 concentration and the heat island intensity data was analyzed,and spatial pattern was also analyzed.The main conclusions are as follows:(1)The spatial distribution characteristics of PM2.5 and PM10 in all districts of Tianjin are basically the same throughout the year,and the overall trend shows a continuous decline.The air quality of the high concentration area is significantly improved.(2)The heat island effect in Tianjin has been strengthened in 2008-2017.The intensity of heat island varies obviously from day to night and from season to season.In the daytime,the heat island effect is stronger in summer and autumn,weaker in spring and winter,and the trend is opposite in the night The medium temperature zone and the higher temperature zone are dominant in the thermal environment of Tianjin.The area of the medium temperature zone and the higher temperature zone obviously increase,and the surface temperature is increasing.In terms of morphology,the shape of the plaque is more complicated during the day than at night.The shape of each thermal level landscape tends to be regular and the shape is simpler.In terms of structure,the degree of polymerization of the landscape patches of various thermal grades increases overall,showing better polymerizability,and nighttime polymerizability is weaker than daytime.(3)There is close correlation between urban heat island and PM2.5 concentration gradually increased.The correlation between the two phases in 2015 and 2017 reached 0.648 and 0.654.The relative correlation between PM10 concentration and surface temperature was relatively weak.Different land use types had different impacts on urban temperature.Cultivated land,woodland and waters have cooled down the thermal environment in Tianjin.Grassland,artificial surface and bare soil have a warming effect on the thermal environment in Tianjin.