塔克拉玛干沙漠腹地夏季夜间稳定边界层特征及其对沙尘气溶胶浓度的影响

Characteristics of the summer nighttime stable boundary layer in the hinterland of the Taklamakan Desert and its effect on dust aerosols concentration

受沙漠下垫面热力性质影响,夜间大气边界层在沙漠区域具有特殊性,其层结稳定度和边界层动力、热力作用显著改变沙尘气溶胶的排放和扩散过程。塔克拉玛干沙漠是亚洲沙尘气溶胶的重要源区,目前对其夜间大气层结稳定度和边界层动力、热力作用对沙尘气溶胶的影响还缺乏定量评估。利用GPS探空和近地面大气观测资料,分析夜间不同稳定度下边界层结构变化及近地面沙尘气溶胶浓度特征,研究了近地面层结稳定度及热力、动力因子驱动沙尘气溶胶变化的作用机理。结果表明:晴、浮尘天气下夜间边界层稳定度可分为弱稳定、强稳定和极强稳定;中性边界层出现在沙尘暴天气下,强天气过程破坏了稳定边界层结构;晴、浮尘天气下,夜间近地层稳定度的提升有利于沙尘气溶胶累积。沙尘暴天气下情况相反。沙尘气溶胶浓度变化由垂直风切变主导,晴、浮尘天气下夜间垂直风切变增强促进了沙尘气溶胶的垂直扩散,降低了近地面沙尘气溶胶浓度;沙尘暴天气下受天气系统扰动垂直风切变与沙尘气溶胶浓度呈显著正相关,有利于本地起沙和上层沙尘向近地面输送,提升了沙尘气溶胶浓度。

Influenced by the thermal properties of the desert subsurface,the nocturnal atmospheric boundary layer in the desert region exhibits significant alterations in stratification stability,boundary layer dynamics,and thermodynamics,impacting the emission and dispersion processes of dust aerosols.Despite being a crucial source of dust aerosols in Asia,there is a lack of quantitative assessment of the effects of nocturnal atmospheric stratification stability,boundary layer dynamics,and thermodynamics on dust aerosols in the Taklamakan Desert.To address this gap,this paper utilizes GPS sounding and near-surface atmospheric observations to analyze the structural changes of the boundary layer and the characteristics of near-surface dust aerosol concentration under different stability conditions during the night.The study also investigates the mechanisms driving the changes in near-surface stratification stability and the thermal and dynamical factors influencing dust aerosol variations.The findings reveal that under clear and floating dust weather,the stability of the nocturnal boundary layer can be categorized as weak,strong,and very strong stability,while a neutral boundary layer occurs during dust storms.The strong weather processes disrupt the stable boundary layer structure.Enhanced stability of the nearsurface layer at night favors the accumulation of dust aerosols under clear and floating dust weather,with the opposite effect observed during dust storms.Vertical wind shear predominantly influences the variation in dust aerosol concentration.This shear is intensified at night under clear and floating dust weather,promoting vertical diffusion of dust aerosols and reducing near-surface concentrations.Conversely,during dust storms,a significant positive correlation exists between vertical wind shear disturbed by the weather system and dust aerosol concentration,facilitating local dust uplift and the transport of upper-layer dust to the near-surface layer,thereby enhancing dust aerosol concentrations.The results of this study will contribute to a deeper understanding of desert land-atmosphere interactions,physical processes in the nocturnal boundary layer,and the impacts of these interactions.