| Urban planning will have an important local climate impact.Among the local climate effect factors of different planning schemes,urban greening and ventilation corridors are two important factors.This article adopts RBLM2.0 model,selects different weather types,and carries out the research on the climate effect and urban greening and ventilation corridor of the new city planning plan of Dajiangdong area in Hangzhou.The main conclusions are as follows:The impact of the new city planning scheme in Dajingdong is embodied in:(1)City Planning scheme 1,2 increases the average ground temperature of the simulated area by 0.69℃ and 0.85℃,and the average air temperature does not change much.Plan 1 increases the temperature in the urban area by 0.2-0.3℃ and the temperature of 130m by 0.05℃.Plan 2 increases the temperature of the urban area of Dajingdong by 0.2-0.5℃ and the temperature of 180m by 0.05℃.(2)The construction of the new city will reduce the relative humidity of the urban area by 0.5-2%.In the planning schemes 1,2,the height of 170m and 210m has a dehumidification of 0.03 g/kg.Summer has the largest drop in specific humidity.(3)The new city planning schemes 1 and 2 reduced the wind speed by 0.11 and 0.12m/s,and the height of 80m and 140m decreased by 0.08 m/s.In summer,the wind speed decreases the largest,and the winter airflow convergence is the most obvious.The plan 1 makes the updraft of the heat island of the Dadongdong urban area obvious,and the speed can reach 0.3 m/s.(4)The temperature rise and humidity drop caused by the construction of the new city are obvious during the day(8:00-16:00),and the impact of the planning scheme 2 is more obvious than planning scheme 1.(5)The strength of the urban heat island in Dajiangdong is small.The difference between urban heat island intensity in each season and weather type between Casel and Case2 is small.The intensity of the heat island in winter is the highest;in the weather type,the heat islands of A,ANE and AE have high intensity.Case1,2 have the highest wind speed difference in the suburbs in autumn;the weather type NE has a high wind speed difference.(6)The planning scheme 1 with large green area has less impact on the climate in Dajiangdong and is highly feasible.However,if the limited area is also developed,it will have an adverse impact on the climate.The influence of urban vegetation on local meteorological elements in Dajiangdong is embodied in:(1)Improving the urban green coverage rate and the proportion of trees can effectively reduce the local temperature of the city,alleviate the heat island effect,and increase the local humidity.(2)The vegetation distribution characteristics in Planning scheme 1 can reduce temperature,increase humidity,and alleviate urban heat island phenomena.In the summer,the vegetation distribution of planning scheme 1 can reduce the average daily temperature of the new city by0.19℃and the average relative humidity by 0.75%.In the winter,the vegetation distribution of planning scheme 1 can reduce the average temperature of the new city by 0.1℃ and the average relative humidity by 0.45%.(3)The local cooling and humidification effects of urban greening rate are different at different times of the day,and stronger in summer than in winter.(4)In the winter and summer,the cooling and humidification effect of trees in the city is better than that of grassland.(5)The impact of the greening scheme on the summer heat island intensity is greater than that in winter,while the urban area grassland ratio change has a greater impact on the winter urban heat island intensity.(6)Based on the simulation results in this chapter,45%of the tree coverage rate,with 90%of the trees and 10%of the grassland,can be used as an optimal solution to effectively alleviate the urban heat island effect.The influence of the ventilation corridor on the local meteorological elements in Dajiangdong is reflected in:(1)The urban ventilation corridor has the effect of reducing the temperature.Compared with no corridors,in summer:the corridor area is cooled by 0.3-0.5℃;at 1000m from the corridor,the temperature is lowered by 0.1 ℃,and the temperature is reduced by0.1 ℃ at a height of 90m.Winter:There is a temperature drop of 0.4-0.6℃ in the urban corridor area;there is a temperature drop of 0.4℃ at 1000m from the corridor,and a temperature drop of 0.1 ℃ at a height of 140m.The cooling effect is most noticeable at noon.(2)Urban ventilation corridors have the effect of increasing local humidity.In summer:the relative humidity of the corridor area increases by 1-2%;the relative humidity increases by 1%from the corridor 1000m.At a height of 80m,the increase in humidity is 0.12 g/kg,and the period in which the effect of increasing humidity is most pronounced occurs during the day.Winter:the relative humidity of the corridor area increases by 2.5-4.5%;the relative humidity increases by 2%at 1000m from the corridor,and increases by 0.02g/kg at a height of 70m.The most obvious period of increasing relative humidity occurs at noon.(3)Urban ventilation corridors have the effect of increasing local wind speed.In summer:the wind speed in the corridor area increases by 0.4-0.6 m/s;the wind speed increases by 0.0 m/s at 500 m from the corridor,and the wind speed increases by 0.05m/s at 70m.Winter:The wind speed in the corridor area increases by 0.2-0.2m/s in winter;the wind speed increases by 0.1m/s at 500m from the corridor,and the wind speed increases by 0.15 m/s at 170m.(4)The cooling and humidification effect of urban ventilation corridors is stronger than that of summer in winter,and the effect of increasing wind speed is strong in summer and winter. |
