CAJ | 학술논문

在北京地区，有一类高污染产生在850 hPa以上为偏北风的背景下.利用气象观测资料、NCEP再分析资料和地面PM2.5浓度监测结果分析了环境气象条件在这类污染过程形成中的作用.结果表明，在污染物浓度逐渐升高的过程中，环境大气并不总是处在层结稳定状态，有利于污染物累积的气象条件来自垂直运动和散度在垂直方向上的“分层”结构.从地面到对流层中层，垂直速度呈上升-下沉-上升的分布，而且散度呈辐合-辐散-辐合的结构.近地层的辐合导致周边的污染物向本地汇集，上升运动则将它们送向空中.但是，叠置在其上空的、长时间维持的下沉气流层却阻止了污染物继续向上运动，从而导致近地面层的污染浓度不断升高.垂直运动出现“分层”是由于高空偏北风并没有侵入到边界层内，近地层仍然维持偏南风或小风，冷空气太弱或者没有冷空气活动是高空偏北风不能到达近地层的主要原因.而下沉气流层的形成则与其上空的空气辐合有关，该辐合层源自偏北气流中的风速脉动.因此，环境大气动力作用是高空偏北气流型空气污染过程形成的关键机制.关注对流层中下层温度24 h变化、垂直速度和散度的垂直分布将有助于提高此类高污染过程的诊断分析和预报能力.
재북경지구，유일류고오염산생재850 hPa이상위편북풍적배경하.이용기상관측자료、NCEP재분석자료화지면PM2.5농도감측결과분석료배경기상조건재저류오염과정형성중적작용.결과표명，재오염물농도축점승고적과정중，배경대기병불총시처재층결은정상태，유리우오염물루적적기상조건래자수직운동화산도재수직방향상적“분층”결구.종지면도대류층중층，수직속도정상승-하침-상승적분포，이차산도정복합-복산-복합적결구.근지층적복합도치주변적오염물향본지회집，상승운동칙장타문송향공중.단시，첩치재기상공적、장시간유지적하침기류층각조지료오염물계속향상운동，종이도치근지면층적오염농도불단승고.수직운동출현“분층”시유우고공편북풍병몰유침입도변계층내，근지층잉연유지편남풍혹소풍，랭공기태약혹자몰유랭공기활동시고공편북풍불능도체근지층적주요원인.이하침기류층적형성칙여기상공적공기복합유관，해복합층원자편북기류중적풍속맥동.인차，배경대기동력작용시고공편북기류형공기오염과정형성적관건궤제.관주대류층중하층온도24 h변화、수직속도화산도적수직분포장유조우제고차류고오염과정적진단분석화예보능력.
There is a kind of serious air pollution case occurring in the situation of northerly flow at the levels above 850 hPa in Beijing area. Meteorological data, NCEP reanalysis data and PM2. 5 concentration survey were used to analyze the roles of meteorological mechanism in this kind of air pollution case. The results showed that the stable stratification did not exist all the time during the gradual increase of PM2. 5 concentration. The favorable meteorological conditions in PM2. 5 accumulation came from the layered structure of vertical speed and convergence in vertical direction. From the surface to the middle level of troposphere, the vertical velocity showed an updraft-downdraft-updraft distribution. And the divergence displayed a convergence-divergence-convergence structure. The convergence at lower levels led to the gathering of the polluted air from the surrounding and the ascending current brought it upwards. However, the polluted air could not go further up due to the prolonged downdraft layer above. As the result, PM2. 5 near the surface was concentrated gradually. The vertical speed in layer structure was attributed to the high level northerly flow without invading into the boundary layer. In such case, the wind was still in southerly direction or kept calm at the surface. The weak cold air or no cold air at all was the main reason that the northerly flow could not hit the surface. The developed downdraft layer was relative to the convergence above which was resulted from the wind speed pulses in the northerly flow at upper levels. In conclusion, the air dynamical effect played a key role in the pollution type of northerly flow at upper levels. Therefore, it will be beneficial to enhance our capability in the analysis and forecasting of this kind of pollution case by focusing on 24 hours temperature variation at the middle and lower troposphere as well as the vertical distribution of vertical velocity and divergence.