关键词: 强浓雾, 逆温, 地形动力, 触发因子

Abstract:

Using 5 min dense observations from automatic meteorological stations, second-level sounding data, wind profile radar data, and ERA5 hourly reanalysis data from the European Centre, the circulation pattern, evolution characteristics, and causes of explosive intensification of a persistent heavy fog event in Guanzhong Plain, Shaanxi from January 10 to 12, 2019 were analyzed.The Results show that this heavy fog event has the characteristics of high intensity, long duration, and explosive enhancement in multiple locations.The highly humid environment after the rain provides favorable water vapor conditions for this heavy fog event.The stable and persisting strong inversion layer causes large amounts of moisture to accumulate near the surface and is difficult to diffuse, which provides favorable stratification conditions for the explosive intensification and persistence of this heavy fog.The convergence of the wind field formed by the special terrain of Guanzhong Plain makes the water vapor fully condense, which is conducive to the development of heavy fog.Triggering factors such as the sudden change of wind direction and the return of cold air near the surface, may have caused the short-term explosive intensification of heavy fog in multiple locations.The preemptive jump of the static stability index before the fog outbreak and the near-surface easterly backflow below 925 hPa under the static and stable weather background can be used as a reference index for the fog outbreak enhancement in this region.

Key words: Heavy fog, Temperature inversion, Topographic dynamics, Trigger factor