| At present,the rapid urbanization is increasing,the urban environment and ecology are also affected,and the urban thermal environment is also deteriorating.The deterioration of geothermal environment in urban built-up districts is getting more and more attention.Under the background of the urban thermal environment,the heat island effect is one of its important research problems.As the most complex and complex public space in the city,the commercial area has high density of people and buildings,and the ecological and sustainable development of its outdoor thermal environment should be paid great attention to.Greening is one of the main ways to improve the geothermal environment of the Urban Bureau,however,there is a lack of quantitative research on the greening of commercial areas and the study of the thermal environmental impact of greening on commercial areas.Therefore,this paper discusses the impact and improvement of greening on the thermal environment of commercial areas from the perspective of climate suitability and ecological sustainable development.By selecting the greening scale and green structure quantitative index of typical business district,this paper establishes a model based on DESIGN Urban Thermal Environment as a simulation platform,and discusses the influence of different greening scale and greening structure on the thermal environment of the commercial area from the three aspects of average heat island strength,WBGT and CTTC based on numerical statistics.Among the problems involved are the selection and definition of green quantitative indicators,the establishment of index system,the measured analysis and verification of simulation software,the design of numerical simulation schemes in typical business districts,and the data collation and analysis of simulation results.The main work and findings are as follows:(1)First of all,at the theoretical level,the research method and evaluation method of the geothermal environment of the local government are introduced,and the calculation model based on the total parameter method based on thermal time constant(CTTC)is determined by the literature review research,and the evaluation index system of thermal environment evaluation and greening planning and design of commercial area is established,which uses the average heat island strength and WBGT as the thermal environment evaluation index.The greening scale index and the green structure index are evaluated from two aspects,among which the greening scale index includes the greening rate,the green shade coverage rate,the roof greening rate three indicators,the green structure index contains a green quantity index of the complex layer.It paves the way for the follow-up study to evaluate the thermal environmental impact of greening on commercial areas.(2)Secondly,the Wanlinghui Business District of Tianhe District,Guangzhou,as a typical business district,through the 24-hour monitoring of the microclimate of the business district measured data and numerical simulation verification,the accuracy of the DESIGN Thermal Urban Environment simulation software based on the set total parameter method is obtained,which provides the basis for the simulation research.The measured verification shows that the simulated value of DUTE is close to the measured value from the average temperature of each measuring point,so the DUTE numerical simulation can better reflect the overall air temperature in the commercial area.(3)Third,the qualitative description and quantitative research combined to summarize and analyze the national relevant business district planning and management documents of the green indicators,and further select the country's four climate zones,a total of 11 typical business districts for DUTE numerical simulation analysis,statistics on the current typical business district construction status quo and the current state of the thermal environment.Research shows: 1)China's cities of the business district greening planning management documents for the business district greening planning indicators,the greening rate of only a simple lower limit control,the greening scale(green coverage,roof greening,etc.)related indicators are only a few cities have more vague provisions,mostly to "encourage construction" mainly.Green structure related indicators have not even been reflected,some indicators need to be paid attention to;2)Through the typical business district greening status statistics found that most of the commercial areas to intensive high-intensity development and construction-oriented,greening the overall structure of a single,mainly to the ground greening-based,green space rate and green coverage of the construction situation is also uneven,a few business district green space rate did not meet the planning indicators of urban business district requirements,individual business districts exist in the form of roof greening,so we need to increase the encouragement of construction,business district greening form needs to be further optimized;3)Through the numerical simulation of the thermal environment of typical commercial areas,it can be seen that most of the 11 typical business district CTTC is above 8.5 with high heat storage capacity,the average heat island strength is mostly between 2-3 degrees C,significantly higher than the existing residential area heat island strength index(?1.5 degrees C);However,the numerical requirements for WBGT(?33 degrees C)have been met.(4)On this basis,according to the greening scale,that is,greening rate,roof greening rate,greening coverage of three indicators,choose five typical business districts as model prototype,and under reasonable premise to change the indicator design model,a total of three sets of 72 models for comparative analysis;Aiming at the green structure,quantifying the green structure of the commercial area from the vertical structure,that is,building a single structure,grass irrigation structure and Joe irrigation structure with a single index,selecting a typical business district as the model prototype,and carrying out different scheme design under the premise of controlling the greening scale unchanged,and establishing three sets of 59 models for comparative analysis.Further DUTE numerical simulation analysis was carried out to compare the average heat island strength,CTTC and other parameters to explore the impact of greening scale on the thermal environment of the commercial area.The research shows that the increase of greening scale has a positive effect on the thermal environment of commercial areas,and the improvement benefit of greening shade coverage is the greatest,followed by the rate of green space and finally the rate of roof greening.The improvement of green structure is an important factor influencing the thermal environment of the commercial area,the improvement effect of the trees on the heat island strength of the commercial area is better than that of grassland and shrubs,the difference between grassland and shrubs is not much,and the increase of the proportion of trees in the combination of joe shrubs is more conducive to alleviating the heat island of the commercial area. |
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