A new analysis of pollution data shows that wind strongly affects Beijing’s PM2.5. The data shows that the best air pollution happens when there are northern winds.
Why would northern winds help? North of Beijing is home to sparsely populated Inner Mongolia.
Thus, PM2.5 in China’s capital tends to drop when the wind blows from the north and northwest (left side of the graph).
Meanwhile, when wind comes from the south or east, PM2.5 tends to be above long-term averages. These northern winds help explain why rain seems to clear out pollution, but actually has almost no effect.
Special thanks to Calvin Quek (Twitter @clearroads), who did the original analysis.