Observation And Numerical Simulation Of The Interaction Between Haze And Ozone In The Urban Area Of Suzhou City

Haze and ozone have become one of the most important pollution problems in the urban area of China.Studying the interactions between haze and ozone in the urban area are of great scientific significance in understanding urban haze,formation mechanism of photochemical smog and improving urban air quality and haze forecasting.Observation data in Suzhou and Nanjing University City Air Quality Prediction System(NJU-CAQPS4.3)are used to study the interactions between haze and ozone in Suzhou City and evaluating the relative importance of these interactions in different seasons.There are very complex interactions between particulate maters and ozone which are called radiative effect,photochemical effect and heterogeneous effect respectively.Radiative effect is that aerosols change meteorological fields through direct radiative forcing and affect the transport and diffusion of ozone.Photochemical effect is that aerosols affect solar radiation and then modify photolysis rate of gases.Heterogeneous effect is that aerosols affect the concentration of ozone by heterogeneous chemical reactions.Direct radiative forcing effect takes into account radiative effect and photochemical effectParticulate matters and O3 in Suzhou City have the feathers of seasonal and diurnal variations which are affected by weather conditions,motor vehicle exhaust emission and photochemical reactions,PM2.5 shows a significant positive correlation with NO2,CO and Ox which shows that automodbile emissions and photochemical reactions have a significant contribution to PM2.5.PM10 and PM2.5 are negatively correlated with clearness index Cl which means that particulate maters can reduce downward solar radiation.There is a significant positive between O3 and DSR which shows the photochemical properties and dependencies on solar radiation of O3.Meanwhile,PM10 and PM2.5 have a negative correlation with O3 which indicates that particulate maters can cut down the concentration of O3.During the period of December 13 to 14,2014,PM10 and PM2.5 increase from 104.3?g·m-3 and 57.2?g·m-3 to 137.3?g·m-3 and 99.9?g·m-3 respectively.DSR lowers from 438.4W·m-2 to 394.8W·m-2.O3 drops to 33.1?g·m-3 from 43.7?g·m-3.It indicates that particulate matters result in the decrease of downward shortwave radiation reaching the ground and O3 concentration further by extinction effect.In the period of November 10 to 13,2014,PM10 and PM2.5 increase from 97.8?g·m-3 and 91.9?g·m-3 to 199.6?g·m-3 and 179.6?g·m-3 when DSR has little changed.O3 drops from 82.5?g·m-3 down to 49.9?g·m-3.It shows that when downward shortwave radiation reaching the ground is almost unchanged,heterogeneous chemical reactions between the particles and O3 result in the lower O3 concentration.Through the study of winter case,we find that radiative effect of particulate matters causes shortwave radiation reduced by 5.4%-22%in the simulated region.Near-surface air temperature falls between-0.25?--0.48?.Turbulent kinetic energy and urban wind speed significantly reduce.Boundary layer height shows reduction of 4%.PM10,PM2.5,sulfate and nitrate in the urban increase by 1.01%,1.01%,1.11%and 1.01%.The changing amplitudes of O3,NO2,NO,NOx and SO2 are-0.99%,0.48%,1.58%,0.73%and 0.71%.Photochemical effect causes in the reduction of 0.07%and 0.26%of sulfate and nitrate respectively and-4.33%,3.59%-8.09%and 0.95%changing amplitudes of O3,NO2,NO,NOx in the urban.Heterogeneous effect causes in the increase of 22.07%and 6.93%of sulfate and nitrate and-4.67%-1.08%,3.08%-0.32%and-13.38%change range of O3,NO2,NO,NOx and SO2.Photochemical effect on O3,NO,NOx and NO2 are greater than radiative effect while particulate matters and SO2 on the contrary.Direct radiative forcing effect(photochemical effect and radiative effect)plays a dominant role in the change of NO2,NO and NOx with respect to heterogeneous effect,while heterogeneous effect is more important in the change of particulate matters and SO2.Both of them have a considerable role in the change of O3.In the case of summer,radiative effect on NO is greater than photochemical effect while the secondary inorganic aerosols on the contary.