| The total population of China's mainland has exceeded 1.39 billion in 2018,of which the proportion of urban population has also reached 60%,and the proportion of urban population has reached a relatively high level.Urban development will bring many problems such as the deterioration of urban climate,worsening urban pollution,and tight land area,which will have a great impact on people's living environment and quality of life.Therefore,we must ensure the sustainable development of urban construction while also taking into account the protection of the urban environment.This paper takes wuhan city as the research object,based on the high-resolution land use data in the fifth period,and with the help of GIS and WRF/UCM platform,explores the impact of urbanization progress on urban microclimate from two aspects: the expansion of urban construction land scope and the change of urban land intensity,and conducts simulation analysis on the microclimate in the future development mode,the research conclusions are as follows:Firstly,The influence of the expansion of urban construction land on microclimate is analyzed without considering the change of urban land use intensity.Wuhan experienced a rapid expansion of urban construction land from 1980 to 2015.After analyzing the research area,it was found that the proportion of built-up area increased from 11.49% to 37.64%.The expansion of urban construction land resulted in a temperature rise of two meters,with a larger temperature increase at night than at day.The proportion of high temperature areas increased significantly,and the newly built areas(especially at night)increased significantly,but the temperature of the original built areas did not change significantly.At 3 PM,the highest temperature,high temperature ratio also reached more than 30%,at 22 PM,the largest increase in the proportion of high temperature(value of about 20%).The proportion of high temperature area has a good positive correlation with the proportion of built-up area,and the correlation coefficient is above 0.9.The wind speed is less affected by the expansion of urban construction land,and the wind speed increases at night while decreases during the day.The expansion of urban construction land will significantly increase the proportion of strong heat island and heat island area at 4 am and 22 PM(over 25% in total).Secondly,under the condition of a certain scope of urban construction land,the influence of urban land intensity change on microclimate was analyzed.In view of the change of urban land use intensity,this paper discusses from two aspects: plot ratio and building density.The increase of floor area ratio will lead to the decrease of temperature in the early morning and daytime,while the increase of temperature at night is mainly concentrated in the second ring road.At 22 pm,the temperature increases,and the proportion of high temperature zone increases with the volume ratio(about 3%-5%).For the wind speed,the increase of the volume ratio will reduce the wind speed,especially the wind speed in the pre-sunrise stage within the three-ring line.The increase of floor area ratio will also lead to the ratio of strong heat island at 12:00 noon and 3:00 PM decreases first and then increases with the increase of floor area ratio,and the ratio of strong heat island at 22:00 PM increases with the increase of floor area ratio.Building density has a more significant effect on microclimate than floor area ratio.The increase in building density will increase the temperature by two meters.The increase in temperature during the day is more obvious than at night.The average value of the former is 0.91 ? and the latter is 0.56 ?.The building density has a wider effect on temperature.The average temperature change in the area outside the Fourth Ring Road during the day is above 0.4 ?;it has a greater impact on high-temperature areas,and the proportion of hightemperature areas at 12 noon and 3 pm increases by more than 15%.There was an increase(around 10%)at 22:00 at night.For wind speed,the increase in building density will increase,especially during the day,and the growth rate in the area outside the fourth ring is more obvious.The increase of building density will increase the mean and peak value of heat island,and increase the action time and range of heat island effect.The proportion of strong heat islands and heat island areas at 12 noon and 3 pm has a significant strengthening effect(value of about 5%).At 22 pm,the proportion of strong heat islands has increased,but the proportion of heat island areas has decreased.Thirdly,a benchmark case based on wuhan city master plan(2010-2020)and a forecast case based on wuhan city master plan(2019-2035)were set up to simulate and analyze the microclimate under the comprehensive development model.Compared with the benchmark case,the temperature of the predicted case will significantly increase at two meters,and the temperature difference of the newly built area is larger at night,while the temperature difference of the original built area is higher at day.The phenomenon of daytime temperature increase was more obvious in the study area than at night,and the mean temperature difference in the three-loop region reached 1.35?.Under the circumstance of the expansion of urban construction land and the increase of land intensity,the wind speed decreases obviously in the night and increases in the day.The intensity and action time of heat island were strengthened,the proportion of heat island at all levels did not change significantly in the early morning,and the proportion of strong heat island and heat island area increased significantly at 12 o 'clock at noon and 3 o 'clock at afternoon,with the former about 10% and the latter about 20%.However,at 22 PM,the proportion of strong heat island area is higher,about 60%,an increase of about 10%,and the heat island phenomenon is significantly worse.On the whole,different aspects of urbanization have different and interrelated effects on microclimate.First of all,without considering the change of urban land intensity,the expansion of urban construction land has more obvious changes in the temperature,wind speed and heat island of the newly added area,and the impact is greater at night than during the day.Secondly,under the condition of a certain range of urban construction land,urban land use intensity mainly plays a role in the microclimate within the scope of the third ring road,in which the building density has more significant influence on temperature and heat island effect than the plot ratio,and the plot ratio has more obvious influence on wind speed.The building density has a dominant effect on the microclimate during the day,while the floor area ratio has a greater influence on the microclimate during the night.Finally,under the condition that the scope and intensity of urban construction land increase at the same time,the temperature of the original built-up area increases significantly during the day,while the temperature of the newly added built-up area increases significantly at night.The regional wind speed decreased significantly at night,and the heat island intensity and action time increased.Therefore,it is necessary to formulate corresponding strategies to alleviate the deterioration of microclimate caused by urbanization progress. |
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