Spatial and Temporal Distribution Characteristics of Dust Devils in the Qaidam Basin

Dust aerosols are significant components of atmospheric aerosols， and they play a crucial role in global weather and climate changes through radiative effects and the formation of cloud and precipitation.The impact of dust devils on the worldwide emissions of dust aerosols should not be underestimated.The Qaidam Desert located in the northern part of the Tibetan Plateau is a source of dust devils.To investigate the meteorology conditions that lead to the occurrence of dust devils and to understand their spatial and temporal distribution characteristics in the Qaidam Basin， the thermodynamic criteria of dust devils are examined using the ERA5 reanalysis data from 1991 to 2020.The spatio-temporal distributions of the potential dust devil and dust plumes occurrence （PDDPhours） across the Tibetan Plateau and the estimation of dust emission caused by dust devils and dust plumes in the Qaidam Basin have been carried out based on these criteria.In the analysis of trends from 1991 to 2020， lapse rate （LR）， convective ratio （w*/u*）， and PDDPhours have been examined.The precipitation from the Delingha National Basic Meteorological Station， PM2.5 and PM10 from the Delingha Air Quality Monitoring Station， and ultraviolet aerosol index （UVAI） data derived from the Aura satellite from 2016 to 2020 have been utilized to investigate the contribution of dust devils to PM2.5 and PM10 in summer in the Qaidam Basin.The results show that w*/u* and LR are the primary factors that influence the formation of dust devils.The PDDPhours reveals a diurnal cycle with peaking at 12:00 -16:00 （Beijing Time） under different thermodynamic conditions.Based on the diurnal variation of the cumulative contribution of PDDPhours， the combined w*/u* > 5 and LR > 10 K·m-1 criteria are considered to be the most appropriate for determining the occurrence of dust devils in the Qaidam Basin.On the basis of the PDDPhours criteria， the analysis highlights the significant presence of PDDPhours in the Qaidam Basin and the southwestern part of the Tibetan Plateau in summer.The results also reveal that the larger dust devil emissions occur in summer with the average dust emission of up to 1.28×105 t， which accounts for 69.8% of annual dust emissions.The lapse rate has shown a significant downward trend and the convective ratio has shown an upward trend in the Qaidam Basin， which finally lead to an obvious downward trend of PDDPhours.The observations indicate that the annual variation of UVAI shows a larger magnitude in summer， despite there is more precipitation in Delingha during this season compared to others.It indicates that， in addition to the dust storm， dust devils may attribute to PM2.5 and PM10 in summer.