[Impact of Atmospheric Circulation Patterns on Ozone Changes in the Pearl River Delta from 2015 to 2020]

Based on the ozone observation data and meteorological reanalysis data of the Pearl River Delta (PRD) from 2015 to 2020, the Lamb-Jenkinson weather typing method (LWTs) was used to analyze the characteristics of different circulation types and quantify their contributions to the interannual ozone variation. The results showed that there was a total of 18 weather types in PRD. Type ASW was more likely to occur with ozone pollution, and Type NE was associated with more serious ozone pollution. To better explore the ozone generation mechanism under different weather types, the 18 weather types were merged into five weather categories based on the wind direction change of the 850 hPa wind field and the different positions of the central system. The weather categories with high ozone concentration were the N-E-S directional category[(161±68) μg·m^-3] and category A[(122±39) μg·m^-3]. The ozone concentrations of these two categories were significantly positively correlated with the daily maximum temperature and the net amount of solar radiation. The N-E-S directional category was the dominant circulation pattern in autumn, whereas category A mostly occurred in spring, and 90% of the ozone pollution events occurring in PRD in spring were related to category A. The contribution of changes in atmospheric circulation frequency and intensity to interannual change in ozone concentration in PRD was 69%, and the contribution of changes in atmospheric circulation frequency alone was 4%. The changes in atmospheric circulation intensity and frequency on ozone-exceeding days contributed comparably to the interannual fluctuations in ozone pollution concentrations.