Differences Among Thermal, Dynamic, and Material Boundary Layers Over Complex Terrain

Abstract

Planetary boundary layers (PBL) characterized by thermal, dynamic, and material types and their spatiotemporal structures were simultaneously detected with ground-based remote sensing instruments in summer by parcel method, Richardson number (Ri), and photoextinction coefficients at Wuhai City. The research site is located at the exit of the valley combined with desert, lake, and the Yellow River, which result in the diurnal variation and inconsistency of three types of PBL. Convective boundary layer (CBL) reaches 3,500 m in daytime while the top of stable boundary layer (SBL) reaches 1,500 m at night. The depth of surface layer, mixing layer (ML), residual layer (RL), entrainment zone (EZ), and temperature inversion are closely correlated with diurnal temperature variation. Substantial variability in CBL and SBL heights up to hundreds of meters was observed in high spatiotemporal resolution. Dynamic PBL representing dynamic stability from Ri fluctuates around 1,000 m during nighttime and rises to about 1,500 m during daytime. Material PBL, representing the distribution of atmospheric substances driven by solar heating, is classified into residual height of material boundary layer and accumulation height of material boundary layer to describe the capacity of dispersion and accumulation affected by CBL and SBL, respectively. Material PBL demonstrates similar trends to the thermal PBL in the daytime ranging from 1,500 to 3,500 m and shows similar variation with dynamic PBL in the nighttime due to orographic winds. This study emphasizes the differences among various kinds of PBL and importance of high resolution in meso-micro scale study of PBL researches.