Research On The Relationship Between Air Quality And Atmospheric Water Vapor In Chengdu

In order to recognize the air quality and its relationship with atmospheric water vapor in Chengdu,and to better predict,prevent and control pollution,this paper uses the ambient air quality index data?AQI?provided by Chengdu Environmental Monitoring Center and the conventional observations provided by the Wenjiang National Climate Station,the ECMWF/NCEP reanalysis data,the L-band sounding water vapor data and the GDAS data.Firstly,the characteristics of air quality change in Chengdu are analyzed,and the relationship between Chengdu air quality and atmospheric visibility and atmospheric precipitable water?PWV?is preliminarily studied.Secondly,the ground-time meteorological elements are used to estimate the PWV,and then the AQI is used to study the effects of meteorological conditions such as precipitation,static weather and solar radiation intensity on air quality and its relationship with atmospheric water vapor.Finally,this paper selects a typical continuous heavy haze process in Chengdu in the winter of 2017.The air quality characteristics of this event and its relationship with water vapor are studied in detail.The main conclusions are as follows:?1?The highest single-day air quality index?AQI?in Chengdu in 2015 was 308, which reached a serious pollution level.The annual distribution of AQI was the highest in winter and lowest in summer,and the most important pollutant was PM_2.5.Atmospheric visibility decreased with the increase of the number of days, and AQI was negatively correlated with atmospheric visibility.The regression fit of visibility and AQI was 65.7%.The highest visibility in summer is 15.084km; the lowest in winter is only 7.470km.In spring and summer,PWV and ozone concentration were significantly negatively correlated from May to August.In autumn and winter,the PWV and PM_2.5/PM₁₀0 concentrations were significantly positively correlated in January and October-November.The period in which water vapor has a greater influence on PM_2.5.5 concentration occurs in January and October.?2?The results show that under the precipitating conditions,the concentration of ozone?O₃?decreases significantly with the increase of PWV,and the positive correlation coefficient between PWV and PM_2.5/PM₁₀,which has been impacted the most with the correlation coefficient decreasing by 47.62%.The negative correlation coefficient between PWV and O₃ is enhanced in spring and weakened in summer and the positive correlation coefficient between PWV and PM_2.5.5 is weakened in autumn and winter.When the atmosphere is at a high static stability state,the PWV change is more significant with the variations of the AQI and other pollutant concentrations.The correlation between PWV and O₃ is different under different solar radiation intensity.With the increase of the solar radiation, the correlation between PWV and PM_2.5/PM₁₀0 changes from positive correlation to negative correlation.?3?The 500hPa zonal circulation is prevalent,and the low-level pressure gradient is small,and the weak wind speed is the large-scale circulation background that causes pollution.In addition,the combination of meteorological conditions such as low horizontal wind speed,small wind shear,stable atmospheric stratification, low mixed layer height and inversion layer leads to increased pollution.According to the backward trajectory mode,the polluted air mass in the winter basin mainly originates from the sinking airflow in the west and the vicinity of the basin and even inside.In the early stage of this smog process,the weather was dominated by smog,and the later smog alternated.The simulation analysis of water vapor backward trajectory shows that the concentration of pollutants in Chengdu area is rising.In addition to the local suspended particulate matter,the pollutant transportation from Gansu and Shanxi is also an important factor.The pollution process from the Bay of Bengal is continuously transported to Chengdu, ensuring the sustainability and development of its polluted weather.In the comparison of the stratified water vapor and pollutants in the sounding,the change of pollutants has a closely correlation with the changes of water vapor in the 3rd,4th and 5th layers?850-5500m?.