• 关键词：沙尘暴  浮尘  气溶胶浓度垂直分布  偏东风  垂直运动  北京

• 基金项目：中国气象局创新发展专项（No.CXFZ2021Z034，CXFZ2022J013）；国家自然科学基金（No.42175184）

• 翟亮
• 北京市气象台，北京 100089

• 雷蕾
• 北京市气象台，北京 100089

• 刘瑞鑫
• 北京市气象台，北京 100089

• 李林
• 北京市气象局大气探测中心，北京 100089

• 孙兆彬
• 北京城市气象研究院，北京 100089

• 李梓铭
• 京津冀环境气象预报预警中心，北京 100089

• 摘要：沙尘天气会危害人体健康并直接影响城市运行，当沙尘天气发生后，针对其清除过程及动力学机制鲜有研究.本文利用北京地区地面观测资料、风廓线雷达数据、四维变分多普勒雷达分析系统（Variational Doppler Radar Analysis System，VDRAS）数据、气溶胶激光雷达监测资料等，对比分析了2018年3月27—28日明显浮尘和2021年3月15日强沙尘暴天气的沙尘清除过程，研究了不同大气环流背景下的沙尘减弱消散动力机制.结果表明，在3月27—28日偏东风天气背景下：①北京地区沙尘浓度垂直分布及变化与高空槽及偏东风的强度垂直分布有紧密关系；②浮尘天气中，偏东风在1~1.5 km之上随高度减弱形成上升气流，与短波槽耦合，将高浓度气溶胶向高空输送；而1 km以下偏东风向 地面风速减小，有利于下沉运动，不利于气溶胶向高层扩散，造成中层浓度降低；③随着2.5 km以下偏东风加强至低空急流，并随高度增加， 上升运动显著增大，高浓度气溶胶被抬至高层并向下游输送，配合气团更迭，完成浮尘清除.而在3月15日强沙尘暴过程中：④沙尘浓度垂直分布变化与上游传输及低层强下沉运动有关，1 km以下沙尘浓度首先下降，主要由低层大气辐散下沉及沉降作用导致，而高空西北气流的 传输作用使得1~2.5 km高浓度沙尘粒子维持时间较长，垂直出现分层结构；⑤冷锋后西北气流天气形势下，沙尘的清除机制在于整层强烈的下沉运动与自然沉降的叠加效应，配合清洁气团更迭，完成清除过程.

• Abstract：Dust weather is harmful to human health and directly affects urban operation. There are few studies on the removal process and dynamic mechanism on dust weather. Based on the ground observation data， wind profile radar data， variable Doppler radar analysis system （VDRAS） data and aerosol lidar monitoring data， the dust removal processes of obvious floating dust on March 27—28， 2018 and strong dust storm on March 15， 2021 are compared and analyzed， and the dynamic mechanism of dust attenuation and dissipation under different circulation background is studied. The study shows that， under the easterly background from March 27 to 28： ① the vertical distribution and variation of dust concentration are closely related to the vertical distribution of high trough and easterly intensity.② In floating dust， the easterly above 1~1.5 km decreases with height to form an updraft， and it couples with shortwave trough to transport the high concentration aerosol to upper layer. While the easterly wind speed below 1km decreases towards the ground direction， which is conducive to the sinking movement and is not conducive to the diffusion of aerosol to the upper layer， resulting in the reduction of middle-level concentration.③ With the easterly wind below 2.5 km strengthening to the low-level jet， the upward movement increases significantly with the increase of height， and the high concentration aerosol is lifted to the upper layer and transported downstream. With the change of air mass， the floating dust is removed.④ on March 15， the vertical distribution and variation of dust concentration are related to the upstream transportation and strong downward motion； the dust concentration below 1000 m decreases first， which is mainly caused by the obvious divergence subsidence and downward motion； the concentration at 1~2.5 km is still high for a long time， which is caused by the transportation from upstream. The dust concentration has a layered structure. ⑤ It is significant for the northerly airflow sedimentation that there are strong downward motion and the dust natural sedimentation in conjunction with the change of the air mass.

• Key words：sandstorm  floating dust  vertical distribution of aerosol concentration  easterly wind  vertical movement  Beijing

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