Influences of a Quasi-stationary Front on Particulate Matter in the Low-latitude Plateau Region in China

ABSTRACT

A comprehensive assessment of the main pollution characteristics of particulate matter (PM) in the low-latitude plateau (LoLaP) region in China by utilizing observation and reanalysis data and statistical methods is presented to reveal influences of the Kunming quasi-stationary front (KMQSF) on PM concentration in LoLaP in winter. It is found that the location and intensity of the KMQSF significantly influenced the distribution pattern of PM and induced high concentrations in some areas in LoLaP region in a typical pollution event in 2016. Furthermore, all the KMQSF synoptic weathers over LoLaP region from 2014-2019 were investigated and classified into 9 Patterns, which led to different air pollution patterns in LoLaP region. When the KMQSF moved westward from middle LoLaP, the PM could be transported to west part of LoLaP by the easterly wind, which led to the daily mean PM₁₀ and PM_2.5 concentrations increase in Kunming, a central city in the west part of LoLaP, at the same time, high concentrations of PM₁₀ and PM_2.5 maintained in Guiyang, a central city locating in the east part of LoLaP. When the KMQSF gradually retreated from west part of LoLaP to east part, the PM in Kunming decreased with a strengthening of the westerly, and the PM in Guiyang further increased with a decrease of the planetary boundary layer (PBL) height and boundary layer dissipation (BLD). When the KMQSF disappeared, the formation of calm inversion pollution could be caused, including a shallow PBL and weak BLD in whole LoLaP, which induced the highest daily mean PM₁₀ and PM_2.5 concentrations both in the two central cities in all patterns.