Relationship between air pollutant distribution and large-scale circulation

Abstract

The Antarctic Oscillation (AAO) has long been linked to the weather and climate of the Northern Hemisphere (NH); however, its linkage with pollutant distribution in China has seldom been discussed. In this study, using the boundary layer structure index (BLSI), NOAA–ESRL and NCEP/NCAR reanalysis data, the effect of boreal summer AAO on pollutant distribution was studied. Regarding the relationship between AAO and pollutant distribution, the Antarctic Oscillation Index (AAOI) was correlated with the dust surface mass concentration (DSMC) of PM_2.5 over China, in which boreal summer (June and July) AAO signals (JJ–AAOI) were selected as the determinant leading factor in establishing a relationship with pollutants during boreal winter (from November to February). The results show that the average of JJ–AAOI has a significant correlation with the DSMC of PM_2.5. August–October were the most significant months over the Antarctic, as indicated by their large coverage of significant areas compared to the coverage of other months. These findings imply that the signals of JJ–AAOI can be stored in Antarctic sea ice up to August–October before they affect the atmospheric boundary layer (ABL), which ultimately affects pollutant distribution in the end. The analysis of the relationship between the DSMC of PM_2.5 and large-scale circulation first involved the use of the empirical orthogonal function (EOF) of the decomposed winter DSMC of PM_2.5. The time series from the EOF1 analysis showed a wave train of four years of positive and negative (+, −, +), followed by a decadal negative value. Moreover, the analysis of the composite difference of meridional circulation between the years of high and low JJ–AAOI shows significant ascending and southerly anomalies at around 25 °N and 35 °N during the higher JJ–AAOI years. These results act as a good starting point for the effort to develop a comprehensive forecasting model for pollutant distribution.