Role of Unbalanced Jet Streak Circulations in East Asian Dust Storms

Abstract

A mesoscale study of three severe dust storms over China and Mongolia was conducted using observational and high- resolution numerical model data sets. The analysis of these data indicates many commonalities among the three case studies, (a) precursor wind flow across the mountain creating a strong statically stable layer in the lee of the mountain, (b) interaction of the exit region of the jet streak with that statically stable layer, (c) breakdown of geostrophic balance of the exit region of the jet streak in the leeside of the mountains, (d) generation of low-level ageostrophic isallobaric wind flow (Vis) as a product of the deep three-dimensional mass/momentum adjustment process, and (e) the development of significant planetary boundary layer (PBL) turbulence kinetic energy (TKE). The isallobaric low-level ageostrophic wind-induced vertical shear and warm buoyant air column heated by surface sensible heat flux led to significant TKE generation resulting in extensive deflation of dust from the surface close to the lee of the mountains (namely Tien Shan, Gobi Altai, and Khangai Mountains). Several dust streaks which resulted from the effects of significant vertical motion and TKE at the meso-γ scale were also observed in response to these adjustment processes.