Formation mechanism of heavy haze-fog associated with the interactions between different scales of atmospheric processes in China

Abstract

Large-scale meteorological processes associated with aerosol pollution can be represented by two parameters: sensitive parameter θe with non-conservative changes and a decreasing mixing layer height (MLH), typically for 3–5 days. Pollution-associated micro-scale processes can be represented by atmospheric condensation rate function and atmospheric super-saturation S to measure the degrees of thermal stability and dynamic dispersion. This shows that the interactions between large- and micro-scale movements in lower atmosphere are critical for the formation of heavy haze-fog, which consists of three progressive processes. In the initial stage, with sufficiently large convective inhibition (CIN), air stratification stabilizes and reduces the MLH. During the micro-scale process, MLH reductions suddenly increase atmospheric super-saturation S, which accumulates additional aerosol by enhancing hygroscopic growth and accelerating secondary reactions. Secondly, from micro-to large-scale process, heat releases during the condensation processes, which is accelerated by an increase in super-saturation, thus, increasing the virtual temperature of ambient atmosphere and decreasing the virtual temperature of the polluted particulate matter. The negative virtual temperature difference δ (T′v−Tv) between the polluted particulate matter and environment further increases as the intensity of S increases with altitude, resulting in larger CIN and consequently more reductions in the MLH. Subsequently, a vicious cycle of increasing super-saturation starts, which again aggravates the haze-fog. This is the basic formation mechanism of heavy pollution under the boundary layer.