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

Large-scale meteorological processes associated with aerosol pollution can be represented by two parameters: sensitive parameter theta e 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 largescale process, heat releases during the condensation processes, which is accelerated by an increase in supersaturation, thus, increasing the virtual temperature of ambient atmosphere and decreasing the virtual temperature of the polluted particulate matter. The negative virtual temperature difference delta (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.