基于多源探测数据对北京一次重污染天气的粒子微物理特征和热、动力机制分析

Particle microphysical characteristics and thermal and dynamic mechanisms of a heavily polluted event in Beijing based on multi-detection data

基于环境、气象、探空、AERONET、云高仪和卫星遥感多数据源对北京春季一次重污染过程的热、动力机制和粒子微物理属性展开研究。结果表明:(1)多源数据协同观测显示本次污染起源于中国西部,影响范围广泛,对北京构成了达6级的重度污染,PM_(2.5)、PM_(10)质量浓度高达600μg/m3和1000μg/m^(3)。(2)MCD19A2 MAIAC AOD能很好地揭示本次污染起源、强度、输送和影响区域,MISR AOD显示本次污染粒子微物理属性具有大模态、非球形、非吸收型的特征。(3)CALIPSO显示,在1~4 km高度,退偏在0.1~0.5,色比在0.5~1.3均有分布,有“小退偏和大色比”现象。(4)AERONET数据显示,污染前、中、后AOD_550 nm值分别为0.9、2.0、0.2,AE_440-675 nm值分别为1.30、0.4、1.0,说明本次污染为PM_(2.5)和PM_(10)混合型污染。(5)探空显示本次污染大气层结非常稳定,各阶段有显著的热动力特征。污染爆发前(5月3日),上层大气潮湿且温度递减率小,低层大气干燥上升,构成对流空间。污染爆发期(5月4日),出现多层逆温,干燥大气下沉运动,受上层西风下层偏南风的动力配合。污染末期(5月5日),低层逆温消失,上层逆温层高度持续抬升,且空气干燥,深厚西风区风速持续加大,终结污染过程。(6)云高仪监测和EC模式结果表明5月4日大气稳定,边界层在空间上分布均匀,08:00大气边界层高度约1200 m,20:00约300 m。

In order to deeply understand the thermal,dynamic mechanism and particle microphysical properties of a heavy pollution process in Beijing in spring,a study was conducted based on multiple data sources of environmental,meteorological,sounding,AERONET,ceilometer remote sensing and satellite remote sensing data.The results are as follows:1)The synergistic observation of multi-source data shows that this pollution originated in the western part of China,with a wide range of impacts,and it constituted a severe pollution up to level 6 in Beijing,with the concentrations of PM_(2.5)and PM_(10)as high as 600μg/m^(3) and 1000μg/m^(3).2)MODIS MCD19A2 MAIAC AOD data can well reveal the origin,intensity,transport and affected area of the pollution.MISR AOD shows that t microphysical properties of the pollution particle have the characteristics of large mode,non-spherical and non-absorption.3)CALIPSO data shows that the depolarization was 0.1-0.5 and the color ratio was 0.5-1.3 at the altitude of 1-4 km,showing the phenomenon of"small depolarization and large color ratio".4)AERONET data shows that before,during and after pollution,the AOD_550 nm values were 0.9,2.0 and 0.2 respectively,and the AE_440-675 nm values were 1.30,0.4 and 1.0 respectively,indicating that the pollution was a mixture of PM_(2.5)and PM_(10).5)Radiosonde data show that the polluted atmospheric stratification of this pollution was very stable,and there were significant thermodynamic characteristics in each phase.Before the pollution broke out(May 3),the upper atmosphere was humid and the temperature decline rate was small,while the lower atmosphere was dry and rose,forming a convective space.During the pollution outbreak period(May 4),there was a multi-layer inversion and dry atmosphere sinking movement.Driven by the upper westerly wind and the lower southerly wind.At the end of pollution(May 5),the inversion in the lower layer disappears,the height of the inversion in the upper layer continues to rise,and the air was dry,and the wind speed in the deep westerly region continues to increase,ending the pollution process.6)The results of Ceilometer monitoring and EC model results showed that the atmosphere was stable on May 4th,and the boundary layer was distributed evenly in space,with an atmospheric boundary layer height of about 1200 m at 08:00 and about 300 m at 20:00.