Double Compressions of Atmospheric Depth by Geopotential Tendency, Vorticity, and Atmospheric Boundary Layer Affected Abrupt High Particulate Matter Concentrations at a Coastal City for a Yellow Dust Period in October

Figure 8

Schematic profile of geopotential height change with time (geopotential tendency (∂Φ/∂ t); m day⁻¹) at 500 hPa level (approximately 5.5 km height) and atmospheric boundary layer (ABL), modified from Choi et al. [28]. Negative geopotential tendency (∂Φ/∂ t) means the decrease of geopotential height for 24 hours (i.e., shrunken atmospheric layer) and vice versa. Positive vorticity (+𝜁=𝜕𝑣/𝜕𝑥−𝜕𝑢/𝜕𝑦) at the 500 hPa level, which implies the downward motion of air toward the ground corresponds to negative geopotential tendency area and vice versa.