Structure of dust and air pollutant outflow over East Asia in the spring

Abstract

Springtime outflow of Asian dust and air pollutants was investigated by a synergetic analysis of ground‐based/space‐borne Lidar observations and numerical models. We identified two prominent outflow patterns, and its occurrence frequency. Pattern I was induced within a typical warm‐sector which lifted up dust particles into the free troposphere, and the existence of two sequential low‐pressure systems played an important role. Pattern II was a ‘behind cold front’ outbreak. Atmospheric stratification was significantly different; Pattern I had weak stratification within the troposphere (potential temperature gradient of ∼2–3.4 K/km), and most of elevated dust layer (typically horizontally 1500–2000 km, vertically 2.5–4 km AGL) remained unmixed with pollutants. Pattern II was characterized by a strong stratification of ∼5 K/km; dust and pollutants were trapped and well mixed within the PBL, forming ‘polluted’ dust. Among the six cases of large‐scale dust/pollutants outbreaks, only two cases are belonged to Pattern I.