An Overview of Triggering Mechanisms and Characteristics of Local Strong Sandstorms in China and Haboobs

Abstract

The local strong sandstorms (LSS), similar to haboobs in Sahara and the North America, often occur suddenly, in tens of minutes during the late afternoon, and before dusk in deserts in China, causing a significant impact on the local atmospheric environment. The Sudan haboob or American haboob often appears in the wet season, followed by thunderstorm events. In contrast, the LSS in China appears most frequently in relatively dry season. The lack of observational data in weather conditions before their formation, during their development and after their disappearance have hindered our understanding of the evolution mechanism of LSS/haboobs. This paper provides a review of the current status and model studies on LSS/haboobs in different time and space to characterize the weather conditions and triggering mechanisms for LSS/haboobs occurrence, as well as highlight the subject for further understanding of LSS/haboobs. LSS are always followed by the occurrence of a dry squall. The interaction of dust radiation heating in the near-surface mixing layer with a mesoscale anticyclone air mass (cold-air pool) in the upper layer is the key process that leads to an LSS. Haboobs are followed by the occurrence of a wet squall. The release of latent heat due to the condensation of water vapor, involving moist convection and cold downdraughts, is the main driving force that cause the occurrence of a haboob. For a better understanding of the characteristics of the wind-sand two-phase flow and the mechanism of energy dissipation in LSS/haboobs, further accumulation of meteorological observation data and small-scale multiple-phase numerical simulations are required.