Study On Meteorological Factors And Air Quality Due To Urbanization In The Yangtze River Delta (YRD),China

Urbanization has a significant impact on momentum and heat transport between the surface and atmosphere,which in turn,influence the dilution and transport of air pollutants,and human health.Recently,impacts of urbanization on climate and air quality have become hot topic,and lots of scientists have focus on it.Analysis of long-term climate data based on observation have been conducted in this study,as well as modeling the urbanization impacts on climate and air quality in YRD region,which including the impacts of changes of land-use,urban canopy,and anthropogenic heat(AH).Firstly,characteristics of climate in YRD region are analyzed base on long-term meteorological data from 1960-2011,of which 29 observation sites are selected.Results show that air temperature increase obviously in mega city sites,with warming rate of 0.69 ?/10a.The lowest warming rate are fund in rural sites with magnitude of 0.40 ?/10a.Warming rate of the minimum temperature is higher than that of the maximum temperature,which implying that the diurnal temperature range(DTR)decreases.Furthermore,decrease of solar duration is also contributed to the decrease of DTR.Wind speed decreases due to urbanization with decrease rate of 0.17 m/s 10a in mega city.Precipitation increase obviously during 1960-2011,with increase rate of 43.3 mm/10a,and about 16-20%increase after 1980s in Mega city.In order to further understand the changes of urban meteorology and air quality due to urbanization,urban land-use data are updated,and parameters in urban canopy schemes are localized,furthermore,anthropogenic heat is estimated in this study.The impacts of urban land-use change on climate and air quality are conducted.Results show that changes of urban land-use modify surface dynamic and thermal processes,exchanges of momentum and heat between surface and atmosphere.2 m temperature(T2)increase during January and July,with magnitude of 1.7 ?and 2.8 ?,respectively.While,the DTR decreases over urban areas,which imply that the increase of temperature is higher during the nighttime than daytime.Wind speed decreases by 23%during January and 13%in July due to increase of surface roughness.Latent heat flux(LH)deceases by 9 W m-2 in January and 72 W m-2 in July due to lower vapor induced by land-use change,while an increase of 76 W m-2 and 33 W m-2 in sensitive heat flux(SH)are fund in our study.Urban-induced precipitation increases by 30?40%in the rainy season,furthermore,a significant increase of precipitation is fund during 13:00 LST?18:00 LST.It seems that convention is strengthened due to land-use change.Regional climate change in turn influence the air quality,results show 30%and 40%decrease of PM10 during January and July,while 6.2%?26.4%and 15.3%?51.2%increase are fund in the simulations,the urban-induced influence on vertical contribution of air pollution could be as high as 1?1.5 km above the surface.The parameters in urban canopy schemes including UCM,BEP,and BEM are updated in order to present local urban morphology.Firstly,modeling results are verified using observation data to facilitate their use.The SLAB and BEM schemes best estimate the meterological and chemical fields.Compared with results from SLAB schemes,BEP and BEM schemes calculate higher T2,heat storage results in increase of temperature during January,while shade effect induced by urban canopy,decreases of temperature are fund in BEP and BEM scheme in July.UCM,BEP and BEM schemes calculate lower wind speed.Due to lower PBLH and wind speed PMio from BEP and BEM schemes decrease with magnitude of 18.6%(22.1?g m-3)and 16.7%(18.3?m-3).Increase of 32.7%(18.3?g m-3)and 30.8%(16.5?gm-3)are fund in BEP and BEM during July.Estimate of AH inventory are conducted in our study,results show that high AH flux are mainly over mega cities such as Shanghai,Nanjing and Hangzhou,with magnitude of 120.4 W m-2?37.7 W m-2 and 83.5 W m-2.Modeling results show that,temperature increases over urban areas with similar patterns with distrubutions of AH.Sensitive heat is the main factor that induces increase of T2.Precipitation also shows 15?30%increase in July.Increase of PBLH result in decrease of PM10,with maximum decrease of 29.3 ?g m-3(24.5%)and 26.6 ?g m-3(18.8%)over Shanghai.Difference of PM10 profile shows an increase of 4?g m-3 between 0.5?1.5 km above surface.Increase of T2 and decrease of NOx induce an increase of ozone,with magnitude of 2.5 ppb(18%)over Shanghai in January and 4 ppb(15%)over Hangzhou in July.Generally,from the past 50 years(1960-2011 years)of long-term changes in characteristics,urbanization has significat impacts on meterological factors.Urbanization induces increase in temperatre,decreases in diurnal temperature range and solor duration.Meanwhile,wind speed and relative humidity decrease and precipitation increases.Changes of land-use due to urban expansion directly modify surface dynamic and thermal properties,the temperature increased significantly in urban areas,and the impact of the summer(July)is greater than in winter(January),near-surface wind speed decreases,convergence strengthened,boundary layer height increases,leading to decreases of PM10 and NOx,while 03 concentration increases.There are different performances on meteorological fields and air pollutants between differernt urban canopy schemes.Compared with observation,the best predictions of meterological and chemical fields are obtained from SLAB and BEM simulation,UCM and BEP simulated larger biases.Anthropogenic heat emission caused by urbanization lead to increases of sensitive heat and surface temperature,convection and vertical mixing in urban areas strengthened.PM 10 and NOx concentration decrease,resulting in an increase in O3 concentrations.Overall,the impact of urbanization brings the dynamic and thermal effects on meteorological factors and atmospheric environment is significant,and must be considered in the urban planning and design,environmental weather forecasting and air pollution control.