Influence of circulation types on temporal and spatial variations of ozone in Beijing.

This study analyzes the impact of circulation types (CTs) on ozone (O ₃ ) pollution in Beijing. The easterly high-pressure (SWW) circulation occurred most frequently (30%; 276 day), followed by northwesterly high-pressure (AN) circulation (24.3%; 224 day). The SWW type had the highest O ₃ anomaly of +17.28 µg/m ³ , which was caused by excellent photochemical reactions, poor diffusion ability and regional transport. Due to the higher humidity and precipitation in the low-pressure type (C), the O ₃ increase (+8.02 µg/m ³ ) was less than that in the SWW type. Good diffusion/wet deposition and weak formation ability contributed to O ₃ decrease in AN (-12.54 µg/m ³ ) and northerly high-pressure (ESN) CTs (-12.26 µg/m ³ ). The intra-area transport of O ₃ was significant in polluted circulations (SWW- and C-CTs). In addition, higher temperature, radiation and less rainfall also contributed to higher O ₃ in northern Beijing under the SWW type. For the clean CTs (AN and ESN CTs), precursor amount and intra-area transport played a dominant role in O ₃ distribution. Under the northeasterly low-pressure CT, better formation conditions and higher precursor amount combined with the intra-area southerly transport to cause higher O ₃ values in the south than in the north. The higher O ₃ in the northwestern area under the northeasterly high-pressure type was influenced by weaker titration loss and high O ₃ concentration in previous day. Annual variation in the CTs contributed up to 86.1% of the annual variation in O ₃ . About 78%-83% of the diurnal variation in O ₃ resulted from local meteorological factors.
(Copyright © 2022. Published by Elsevier B.V.)