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

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 (PM_2.5) 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.