The 10-to 30-Day Intraseasonal Weather Process Associated With Wintertime PM2.5 Pollution in Eastern China

Severe PM2.5 pollution strikes winter eastern China, while its physical process associated with the atmospheric evolution from several days to weeks is not clear. This study uses weather types as intermediate agents between large-scale atmospheric circulation and regional air pollution, to explore the whole circulation evolutionary chain related to wintertime PM2.5 pollution in eastern China. We extract objectively 6 weather types (WTs) for wintertime surface synoptic patterns in eastern China and analyze quantitatively the impacts of WTs on PM2.5 pollution. Then the preferred transitions between WTs are explored to explain potential weather process. We find a most frequently recurring circulation evolution corresponding to Mongolia high pressure that stretches southward to eastern China, referred as the WTs transition of YSH- > BLH- > MH, with PM2.5 increased in North China and dissipated as the high pressure moves southward. Further to establish intraseasonal connections between large-scale circulation and regional synoptic patterns, several leading evolutionary chains are discovered among tropical Madden-Julian Oscillation (MJO), extratropical teleconnections, and WTs of eastern China at an extended period. The positive or negative phase of teleconnections can indicate the WTs change 4-10 days in advance, while MJO further extends that indicative effect to 10-15 days. The intraseasonal oscillations of teleconnections such as conventional Eurasia, Scandinavia, Arctic Oscillation, Polar/Eurasia, Western Pacific and East Atlantic are associated with the transition of YSH- > BLH- > MH, and MJO may act as a precursor of teleconnection phases to extend effectively the prediction time for surface weather conditions and air pollution in eastern China.

Automated summary

This study explores the relationship between large-scale atmospheric circulation and regional air pollution in eastern China during winter by using weather types as intermediaries. The research finds that the most common circulation evolution leading to PM2.5 pollution is the southward movement of Mongolia high pressure into eastern China. Additionally, the study discovers connections between tropical Madden-Julian Oscillation, extratropical teleconnections, and weather types in eastern China, which can help predict surface weather conditions and air pollution in the region.