| In recent years,the serious atmospheric pollution in Jing-jin-ji and its surrounding regions has occurred frequently.The problem of regional air pollution has already caused serious impact on the sustainable development of the city,the ecological environment and human health.The key scientific issues such as the transmission mechanism of regional pollution and the role of geographical and meteorological conditions in formation of heavy pollution are not clear,and the assessment of transport flux in regional pollution transport was not accurate.This series of problems seriously restrict the understanding of the law of the development of air pollution.Lidar detection was mainly used for fixed-point detection in the early stage,and it has gradually developed into urban to regional network monitoring in recent years.Lidar can provide profile data on individual cities or key transmission channels.Qualitative analysis of transport flux can be carried out,but quantitative analysis cannot be carried out,which limits the ability to detect and analyze physical and chemical properties on any path.On the other hand,air quality models development rapidly in recent years,but due to the pollutants emission inventory,meteorological data and model itself exists many factors such as the hypothetical conditions,makes the model simulation of PM2.5 is greater uncertainty.With the development of assimilation technology,the accuracy of model simulation can be improved,but at present,the main focus at home and abroad was the assimilation of ground observation(PM2.5)and satellite remote sensing data(AOD).However,there was little progress in data assimilation of lidar.Therefore,this paper mainly studies the three-dimensional assimilation based on lidar.In this paper,for evaluating the flux of air pollution in the region and revealing the evolution law of meteorological and atmospheric pollution in the boundary layer,the quality control system of multiple data was constructed and the results of the lidar inversion were optimized by using ground-based netted particulate lidar and vehicle mounted lidar system.Combined with WRF-Chem,GSI only for ground PM2.5 assimilation was developed,and a stable and reliable GSI-Lidar was formed to achieve assimilation of PM2.5 stereo detection data and break through the qualitative and quantitative analysis ability of lidar.The three-dimensional PM2 5 fields after the lidar data assimilation was given to obtain the characteristics of the pollutants on the key transmission channels of Jing-jin-ji and its surrounding regions,to establish the accurate analysis method of the transport flux,to carry out the quantitative and comprehensive analysis of the regional pollution transport,to restore the process of the heavy pollution in the region,and to develop a three-dimensional visualization display.First,12 networking lidars and two vehicle mobile lidar are assimilated by data.The results showed that the correlation increased by 42.9%on average and RMSE decreased by 50.9%,which verified the reliability and accuracy of GSI-lidar assimilation system.Secondly,the results of the six months of autumn and winter 2017 indicate that the main transport channel of PM2.5 in Jing-jin-ji was the southwest channel.The pollutants were transferred to Beijing through Handan,Xingtai,Shijiazhuang and Baoding.The secondary transmission channel was the eastern channel(Tangshan).The lowest transport for the southern and southeast passage.Meanwhile,in addition to the accumulation of local emissions,the transportation of external pollution caused by the systematic southerly wind was also the main cause of pollution.Main pollutants in Taihang piedmont city take form accumulation and transmission,transmission channels have obvious order each urban particulate contamination,under the wind city pollution condition on the wind had significant effect on the urban air quality.Finally,compared with the same period in 2016,the pollution transportation and peak value in 2017 were significantly reduced.In the autumn and winter of 2017,in the early stage of pollution formation,the Jing-jin-ji region was mainly dominated by southerly wind(southwest wind or south wind),with low wind speed and obvious boundary layer reduction and temperature inversion.In terms of the amount of transportation to Beijing,Taihang mountain decreased by 64.5%to Beijing on average,while Yanshan decreased by 63.3%to Beijing on average.From the perspective of Beijing's outward conveyance,the direction of Beijing to Taihang mountain and Yanshan mountain decreased by 59.6%and 78.2%respectively.It shows that the joint defense and joint controls in the winter of 2017 has achieved a significant effect. |
PDF Full Text Request