Minzhong Wang

The entrainment zone (EZ) governs the exchange of heat, momentum, and mass between the mixed layer and free atmosphere, shaping dry convective boundary layer (CBL) evolution. Although dry CBL depth ( z _i ) is a fundamental dynamical scale, how it regulates entrainment under different geostrophic winds ( U _g ) and stratification has not been systematically examined. A series of large‐eddy simulations (LES) is employed to address this gap. The main findings are as follows. (a) Regardless of z _i , wind shear plays a dual role in entrainment dynamics: reducing heat transport and entrainment efficiency, suppressing entrainment, limiting CBL growth, and lowering entrainment heat flux ( δQ ) under weak winds. Once wind shear exceeds a threshold, substantially enhanced turbulent kinetic energy (TKE) above the mid‐entrainment layer strengthens entrainment, promoting the growth of δQ and z _i . (b) The deepening of the z _i weakens shear within the EZ, suppressing entrainment under strong U _g . Consequently, differences between strong‐wind and calm conditions in δQ , z _i , and other key parameters diminish. (c) The discrepancy between LES and the shear‐free zero‐order model grows with z _i ; however, for shallow CBL with moderate shear, the model remains valid. (d) The increase in δQ and entrainment heat flux ratio with z _i under strong surface heating and moderate U _g likely arises from more vigorous free convection in a deeper CBL. (e) The nondimensional EZ thickness decreases with z _i , as the lower EZ portion ratio remains nearly constant and the upper part ratio shrinks. These findings clarify the dependence of entrainment on z _i in a sheared dry CBL.

The dune density is an important parameter for representing the characteristics of desert geomorphology, providing a precise depiction of the undulating topography of the desert. Owing to the limitations of estimation methods and data availability, accurately quantifying dune density has posed a significant challenge; in response to this issue, we propose an innovative model to estimate dune density using a dune vertex search combined with four-directional orographic spectral decomposition. This study reveals several key insights: (1) Taklimakan Desert distributes approximately 5.31 × 10⁷ dunes, with a linear regression fit R² of 0.79 between the estimated and observed values. The average absolute error and root mean square error are calculated as 25.61 n/km² and 30.48 n/km², respectively. (2) The distribution of dune density across the eastern, northeastern, southern, and western parts of the Taklimakan Desert is relatively lower, while there is higher dune density in the central and northern areas. (3) The observation data constructed using the improved YOLOv8s algorithm and remote sensing imagery effectively validate the estimation results of dune density. The new algorithm demonstrates a high level of accuracy in estimating sand dune density, thereby providing crucial parameters for sub-grid orographic parameterization in desert regions. Additionally, its application potential in dust modeling appears promising.

Stable boundary layer height (SBLH) is an important parameter to characterize the characteristics and vertical structure of the nocturnal lower atmosphere at night. The distribution of SBLH has obvious spatial and temporal differences, and there are many meteorological factors affecting the SBLH, but at present, there are few quantitative studies on the effects of near-surface meteorological factors on the SBLH in the desert hinterland. This study was based on GPS sounding balloon data, near-surface meteorological observation data, and ERA5 data from Tazhong Station (TZ) in the Taklamakan Desert (TD) collected in July 2017, 2019, and 2021. The variation characteristics of the SBLH and its relationship with near-surface meteorological factors are described. We quantitatively analyzed the degree of influence of near-surface meteorological factors affecting the SBLH and verified it using a model. The study also elucidates the possible formation mechanism of the SBLH in the TD hinterland. The SBLH in the TD hinterland trended upward in July 2017, 2019, and 2021, which is consistent with the changes in meteorological factors, according to the near-surface meteorological observation and ERA5 data. Therefore, we think that an inherent connection exists between near-surface meteorological factors and the SBLH. The results of correlation analysis show that complex internal connections and interactions exist among the meteorological factors near the ground; some thermal, dynamic, and other meteorological factors strongly correlate with the SBLH. Having established the change in SBLH (ΔSBLH) and in major thermal, dynamic, and other meteorological factors (Δ), the linear regression equation between them revealed that near-surface meteorological factors can affect the SBLH. The dynamic factors have a stronger influence on the ΔSBLH than thermal and other factors. The results of model validation based on the variable importance projection (VIP) also confirmed that the SBLH in the TD hinterland is jointly affected by dynamic and thermal factors, but the dynamic factors have a stronger impact. The mechanism through which the SBLH forms is relatively complex. At night, surface radiative cooling promotes the formation of a surface inversion layer, and low-level jets strengthen wind shear, reducing atmospheric stability. The combined effects of heat and dynamics play an important role in dynamically shaping the SBLH. This study helps us with accurately predicting and understanding the characteristics of the changes in and the factors influencing the SBLH in the TD hinterland, providing a reference for understanding the mechanism through which the SBLH forms in this area. At the same time, it provides a scientific basis for regional weather and climate simulation, meteorological disaster defense, air quality forecasting, and model parameterization improvement.