摘要
对2005年和2006年北京地区春季没有沙尘和云影响下17次晴空大气气溶胶(粒径范围0.1～3.0μm)飞机垂直观测资料进行分析,给出了三种天气条件(地面高压、地面两高压之间和地面低压)下气溶胶的垂直分布,并计算了对应天气条件下的风通量和理查森数。结果显示:在北京地区处于地面高压控制下(简称类型1),气溶胶的垂直混合和水平传输都很强,气溶胶浓度垂直分布平坦,地面气溶胶浓度平均约为1200个/cm^3;在北京地区处于地面两高压之间(简称类型2),气溶胶的垂直混合较强,边界层上没有阻挡,气溶胶浓度随高度递减,地面气溶胶浓度平均约为7200个/cm^3;在北京地区处于低压控制下(简称类型3),气溶胶在边界层顶垂直混合较弱,形成一个较强的阻挡,阻碍了气溶胶从边界层内向自由层扩散,同时边界层内水平传输较弱,结果是在边界层以上气溶胶浓度迅速递减,地面气溶胶浓度非常高,约为10000个/cm^3。
In this study,aerosol（0.1-3.0μm） vertical distributions of 17 in-situ aircraft measurements during 2005 and 2006 springs are analyzed.The 17 flights are carefully selected to exclude dust events,and the analyses are focused on the vertical distributions of aerosol particles associated with anthropogenic activities. The results show that the vertical distributions of aerosol particles are strongly affected by weather and meteorological conditions,and 3 different types of aerosol vertical distributions corresponding to different weather systems are defined in this study.The measurement with a flat vertical gradient and low surface aerosol concentrations is defined as type-1;a gradually decrease of aerosols with altitudes and modest surface aerosol concentrations is defined as type-2;a sharp vertical gradient（aerosols being strongly depressed in the PBL） with high surface aerosol concentrations is defined as type-3.The weather conditions corresponding to the 3 different aerosol types are high pressure,between two high pressures,and low pressure systems（frontal inversions）,respectively.The vertical mixing and horizontal transport for the 3 different vertical distributions are analyzed.Under the type-1 condition,the vertical mixing and horizontal transport were rapid,leading to a strong dilution of aerosols in both vertical and horizontal direc- tions.As a result,the aerosol concentrations in PBL（planetary boundary layer） were very low,and the vertical distribution was flat.Under the type-2 condition,the vertical mixing was strong and there was no strong barrier at the PBL height.The horizontal transport（wind flux） was modest.As a result,the aerosol concentrations were gradually reduced with altitude,with modest surface aerosol concentrations.Under the type-3 condition,there was a cold front near the region.As a result,a frontal inversion associated with weak vertical mixing appeared at the top of the inversion layer,forming a very strong barrier to prevent aerosol particles being exchanged from the PBL height to the free troposphere.Therefore,the aerosol particles were strongly depressed in the PBL height,producing high surface aerosol concentrations.
出处
《气象》
CSCD
北大核心
2011年第9期1126-1133,共8页
Meteorological Monthly
基金
北京市优秀人才培养项目(20081D0200800058)
北京市优秀人才培养项目(20071D020800058)
国家重点基础研究发展计划项目(2011CB403401)共同资助
关键词
气溶胶浓度
垂直分布
飞机观测
北京
aerosol concentration
vertical distributions
aircraft measurements
Beijing
