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    东北冷涡背景下沙尘天气微气象学及输送特征的观测研究

    Observations on micrometeorological and transport characteristics during dust events under the background of Northeast China Cold Vortex (NCCV)

    • 摘要: 东北冷涡是影响中国东北地区的重要天气系统之一,然而目前对冷涡背景下沙尘天气的形成及输送特征认识不足。本文利用2023年春季沈阳地区气象要素和沙尘参量的立体观测资料,结合后向轨迹分析,研究了东北冷涡背景下三次不同强度的沙尘天气过程中微气象学和沙尘输送的变化特征及近地面湍流的作用机理。结果表明:受东北冷涡影响,沙尘天气发生前近地层湍流活动旺盛,冷涡系统诱发降水,导致环境湿度明显增加,这与无冷涡影响的沙尘天气不同。扬沙天气起沙阶段,低层大气呈热力不稳定,近地面沙尘浓度随摩擦速度(u*)和湍流动能的增加而明显增大,以局地起沙为主;4月11日过程后期受弱风和高湿环境影响,细颗粒物(PM2.5)占比增大,出现沙尘—霾混合污染。与扬沙天气相比,浮尘天气起沙阶段大气处于稳定层结状态,近地面u*与沙尘浓度未出现明显的协同变化关系,沙尘以外源输送为主。后向轨迹分析结果表明,三次沙尘天气均受不同程度沙尘外源输送的影响,沙尘粒子随高空西北气流经蒙古国等地向东北地区输送,气溶胶输送高度集中在1.0~1.5 km之间。

       

      Abstract: Northeast China Cold Vortex (NCCV) is one of the important weather systems affecting Northeast China.However,there is still limited understanding on the formation and transport characteristics of dust events under the NCCV background.Using the three-dimensional synchronous observational data of meteorological elements and dust parameters in Shenyang in the spring of 2023,combined with backward trajectory analysis,we analyze the characteristics of micrometeorological conditions and dust transport and reveal the impacts of near-surface turbulence during three dust events of different intensities under the influence of the NCCV.The results show that affected by the NCCV,near-surface turbulence activity was vigorous before the occurrence of dust events.The cold vortex system induced precipitation and made the ambient humidity increase,which is different from dust events without the influence of the NCCV.During the dust emission stage of the two blowing-sand events,the lower atmosphere was thermally unstable,and the dust concentration increased significantly with the enhancement of friction velocity (u*) and turbulence kinetic energy,mainly due to local dust emission.In the later stage of the blowing-sand event on 11 April,affected by weak winds and high humidity environment,the proportion of fine particulate matter (PM2.5) increased,and dust-haze pollution coexisted.Compared with blowing sand events,the atmospheric stratification was stable during dust emission stage of the floating dust event,and there was no significant synchronous variation relationship between u* and dust concentration near the surface,meaning dust transport from external sources.The results of the backward trajectory analysis showed that the three dust events were all influenced by dust external sources to varying degrees.Massive dust aerosols were transported to Northeast China by the upper-level northwesterly airflow through Mongolia and other places,with the aerosol transport height concentrated between 1.0 and 1.5 km.

       

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