| Affected by the increase in pollution source emissions and adverse weather conditions,the regional air pollution problem dominated by PM2.5 has become increasingly prominent.In particular,the rapidly developing urban agglomerations led by Beijing,Tianjin,and Hebei have experienced serious short-term pollution incidents.The frequent occurrence of air pollution incidents not only harms human health,but also has a serious negative impact on people’s production and life.The pollution sources in the Beijing-Tianjin-Hebei region mainly come from coal burning,industry,motor vehicles and dust,accounting for about 90%.In addition,affected by the heating season,the monthly average emission level of PM2.5 in autumn and winter in the Beijing-Tianjin-Hebei region is 1.5 to 4 times that of the non-heating season.Meteorological conditions mainly provide external conditions for the transformation of pollutants in the ambient air,which are likely to cause sudden pollution events and seasonal pollution characteristics.The circulation situation has a direct effect on the change and distribution of meteorological elements,and directly affects the duration and severity of the pollution process.Therefore,through the study of the temporal and spatial characteristics of PM2.5 concentration and circulation classification in the Beijing-Tianjin-Hebei region,we can further understand the temporal and spatial characteristics of PM2.5 in the Beijing-Tianjin-Hebei region,and provide a scientific basis for refined pollution prevention;By preliminarily understanding the diffusion and accumulation laws of PM2.5 in different circulation situations,it can provide a theoretical reference for early warning and forecasting when serious pollution occurs.At the same time,it provides a scientific basis for the control and prevention of air pollution in the Beijing-Tianjin-Hebei region.This article uses the observational PM2.5 concentration data from the Beijing-Tianjin-Hebei region from 2015 to 2018 and the synthetic data set of surface PM2.5 in China published by the atmospheric composition analysis project group of Dalhousie University to analyze the Beijing-Tianjin-Hebei region in recent years The temporal and spatial distribution of PM2.5,discussing the time-to-time,inter-annual and seasonal variation characteristics of PM2.5concentration;using NECP/NCAR reanalysis data to calculate the geostrophic wind and vorticity values in the Beijing-Tianjin-Hebei region from 2015 to 2018,and Based on the Lamb-Jenkinson circulation classification method,the daily circulation situation is obtained.Then,the results of the circulation classification were classified and analyzed,and the inter-annual and seasonal variation characteristics were explored;the classification statistics of the daily average PM2.5 concentration value≥115μg/m~3(moderate occurrence)Circulation situation at the time of the above pollution),from the perspective of weather background(different height potential fields),analyze the circulation situation with a higher probability of occurrence of moderate or higher pollution.Finally,through the screening of individual cases,the characteristics of the physical parameter fields(wind field,air pressure,humidity,potential temperature)of the circulation situation with a higher probability of occurrence of moderate or higher pollution are studied;At the same time,based on the characteristics of regional pollution in the Beijing-Tianjin-Hebei region,certain countermeasures and suggestions for regional air pollution prevention and control work are put forward.The main conclusions of the paper are as follows:(1)From the perspective of the temporal and spatial characteristics of PM2.5 in the Beijing-Tianjin-Hebei region:the time-to-time changes of PM2.5 concentration in the Beijing-Tianjin-Hebei region from 2015 to 2017 showed a"double peak and double valley pattern",and in 2018 it showed a"single peak and single valley pattern"feature.The former PM2.5 concentration peaked around 10:00 and 23:00-1:00,showing a"double peak and double valley"characteristic change,around 05:00 and 14:00-17:00.The segment is reduced to the minimum value.Shows the"single peak and single valley type"characteristic changes,the peak and valley values are in the range of 23:00-1:00 and 14:00-17:00 respectively;with the increase of time,the maximum PM2.5 concentration year by year Reduced,the scope of pollution impacts is constantly shrinking;the degree of pollution in different seasons is:winter>autumn>spring>summer;from the spatial distribution,the PM2.5 concentration in the study area is manifested from low to high:north>central>south.(2)According to the results of circulation classification,there are 25 circulation types in the Beijing-Tianjin-Hebei region from 2015 to 2018,of which 17 circulation types have an occurrence frequency of less than 4%,and 8 circulation types with an occurrence frequency of6%or more are:A(14.17%),C(9.31%),N(8.90%),W(8.21%),SW(7.32%),NE(6.78%),E(6.23%),NW(6.16%);research period The inter-annual variation of the main circulation types in the interior is irregular,but the annual variation range is between±14.The dominant circulation types in the four seasons(spring,summer,autumn and winter)in the Beijing-Tianjin-Hebei region are A-type and W-type,C-type,A-type,and A-type respectively.(3)Under the control of W-type,A-type,C-type and SW-type circulation in the Beijing-Tianjin-Hebei region from 2015 to 2018,there is a high probability that the average daily PM2.5concentration value≥115μg/m~3;Among them,under the control of Type A circulation,the ground in the study area is mainly controlled by the weak continental high pressure,combined with the westward airflow,and the blocking of the Taihang Mountains can easily aggravate the accumulation of pollutants,forming regional moderate and above pollution;in the control of Type C circulation Under the control of the W-shaped atmospheric circulation,the Beijing-Tianjin-Hebei region is mainly affected by the southwest wind,the wind speed is weak,the air pressure is stable,and the airflow trajectory is almost close to the ground.Conducive to the transportation of pollutants from the central and southern regions of North China to the study area,and fine particle pollution aggravates;under the control of SW-type atmospheric circulation,the upper air in the Beijing-Tianjin-Hebei region is mainly controlled by a single air mass,which is affected by the prevailing flat westerly airflow,which is not conducive to the eastward movement of fine particles Going south,the southwest air current on the ground is conducive to the transportation of pollutants from the central and southern parts of North China to the study area,and it is easy to increase air pollution.Based on the above research and comprehensively related research on the characteristics of the chemical components of the receptor PM2.5,source analysis,and pollutant transmission flux.It is suggested that the prevention and control of air pollution in the Beijing-Tianjin-Hebei region should mainly use coordinated development as an opportunity to further strengthen regional joint prevention and control.According to the spatial distribution characteristics of PM2.5,focus on promoting the management of scattered coal in Hebei Province,using regional transmission channels to further optimize the industrial layout,and at the same time improve pollutant observation methods,strengthen air quality forecasts,and ensure regional air pollution prevention and enterprise production development. |
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