Spatial And Seasonal Variation And The Driving Mechanism Of The Park Green Space Thermal Effect In Zhengzhou

As the world’s population grows and urbanization intensifies,urban construction land expands continuously,the surface energy balance of urban areas is seriously altered,and the urban thermal environment continues to deteriorate.Urban park green spaces play an indispensable role in improving ecological functions and regulating urban microclimate and are widely considered to be extremely effective in mitigating the urban heat island effect.A scientific understanding of the variations and drivers of land surface temperature in different urban parks can help urban planners and decision-makers to develop evidence-based planning,construction and urban management strategies that can improve urban sustainability.However,systematic research on the difference in land surface temperature and its influencing factors from the perspective of park category was limited in the past.This paper takes the main urban area of Zhengzhou City as the study area,based on multivariate remote sensing data and survey data,and generally considered the vegetation characteristics and landscape patterns,including tree and shrub characteristics parameters,diversity parameters,park landscape characteristics and external morphological characteristics,with data analysis and Boosted Regression Trees(BRT)model,quantified the correlation,relative contribution and marginal effect of each influencing factor on the land surface temperature in all seasons to explored the driving mechanisms and regulation strategies of the land surface temperature in urban parks.The results show that:(1)There is a significant moderating effect of urban parks on the surface thermal environment.The park plays a cooling effect in spring,summer and autumn,with a cooling effect of-0.65,-1.41 and 2.84℃ respectively;in winter,it shows a warming effect of 1.92℃.The land surface temperature of the park varies slightly in each season,but the overall spatial distribution shows a trend of high temperature in the east and west and low temperature in the north and south due to the influence of urban building density and the rivers.(2)The land surface temperature of pocket parks,comprehensive parks,large parks and waterscape parks was significantly lower than that of other parks.The contribution of landscape pattern to the variation of the land surface thermal environment in spring,summer and winter is greater than that of vegetation characteristics,while the contribution of vegetation characteristics to the variation of the land surface thermal environment is greater in autumn.(3)Vegetation characteristics contributed significantly to the variation of land surface temperature in summer and autumn.Trees had a stronger effect on reducing land surface temperature than shrubs,and the contribution of vegetation diversity was weaker.The increase in the number and species of trees could decrease the land surface temperature by 1.5℃ and 0.6℃respectively.The tree under crown height and tree height also had a negative effect on the land surface temperature within the corresponding range and the effect was stronger in summer and autumn,and weaker in winter and spring.When the height of the shrub is greater than 1.5-2m in summer,it can reduce the land surface temperature by 0.12℃,and the increase of species diversity can also reduce the land surface temperature by up to 0.4℃ and this adjustment effect is stronger in winter and spring.(4)The increasing effect of landscape patterns on land surface temperature was stronger in spring and summer,but the cooling effect was significant in spring and autumn.The increase in park perimeter,average patch area and shape index had a significant effect on the decrease of land surface temperature,and the contribution is greatest in summer and winter.The proportion of vegetation and water in parks also showed a significant negative correlation with the land surface temperature,which was stronger in spring and summer.The increase in the proportion of vegetation and water could bring a 0.08-0.1℃ decrease in the park land surface temperature.In summer,the proportion of impervious surface increases the park land surface temperature most,and when the proportion of impervious surface is 18%-25%,the land surface temperature of parks can rise by up to 0.2℃.In allusion to the influence of various factors on the land surface temperature of different types of parks,our paper combined the correlation analysis and Boosted Regression Trees model to provide targeted suggestions and strategies for urban park planning from the perspective of mitigating the urban thermal environment.It is of great practical significance to fully understand the urban thermal environment change and its mitigation approaches combined with the previous theoretical progress and put the latest theory into practice in combination with the actual situation for mitigating the urban surface heat effect.