Physical Mechanisms of Deep Convective Boundary Layer Leading to Dust Emission in the Taklimakan Desert.

Deserts play an important role in the climate system, which is closely associated with the emission and transport of dust aerosols. Based on the intensive observation experiment in the Taklimakan Desert, the potential physical processes between the deep convective boundary layer (CBL) and dust emission are revealed in this study. Deep CBL enables the formation of clouds in the late afternoon, leading to significant cooling of surface. Large‐scale buoyant coherent structures thereby transform into the mechanical coherent structures confined near the surface. The responses promote the earlier occurrence of low‐level jet (LLJ) than in cloudless conditions, which allows the downward transport of LLJ momentum and substantially increases surface wind. Therefore, dust emission is initiated by strong wind at dusk and lasts for several hours. The results are useful to predict dust emissions and improve our understanding of distinctive boundary‐layer processes in desert regions. Plain Language Summary: Desert is a key component of regional/global climate system, which is closely associated with the emission and transport of dust aerosols. A better understanding of dust emission mechanisms and their interaction with atmospheric physical processes is of great significance for improving numerical weather and climate models. This study investigates possible physical mechanisms of the dust emission related to deep atmosphere boundary layer, based on the field experiment in the Taklimakan Desert. It is found that the formation of late‐afternoon clouds and the occurrence of wind maxima at 400–600 m are crucial during the processes. Initially, the formation of clouds is enabled by deep atmosphere boundary layer that developed in the late afternoon. After cloud formation, surface becomes cooling, and then the upper part of the boundary layer is gradually released from the surface frictional restraint, which promotes the development of wind maxima at 400–600 m. As the momentum of the wind maxima is transported downwards, surface wind substantially increases, which systematically blows dust particles up. Consequently, dust emission happens at dusk in desert regions. Key Points: Deep convective boundary layer enables the lifting condensation of moisture and the formation of boundary‐layer clouds in desert regionsThe emergence of late‐afternoon clouds strengthens the surface cooling and thus advances the development of low‐level jetDownward momentum transfer from low‐level jet to near‐surface wind is crucial to initiate dust emission at dusk [ABSTRACT FROM AUTHOR]