This article includes supplemental data for the main article “So You Thought Hong Kong’s Pollution Comes From the Mainland?”
This supplemental data will show how high and low wind speeds affect the PM2.5 levels and hence Hong Kong’s pollution. Ultimately, this supplemental article draws the same conclusion as the main article.
Does Wind Speed Affect PM2.5?
What if particulate matter can only be transported at high speeds? In order to test if wind speed affects PM2.5, I repeated the analysis for PM2.5 data at wind speeds below average and above average.
The data shows that lower wind speeds in Hong Kong almost always correlated with lower PM2.5 levels, regardless of the wind direction.
However, this also shows that air pollution was significant even without strong winds blowing PM2.5 from Mainland China. This means that there are PM2.5 sources within Hong Kong as well.
When wind was blowing at higher speeds from the direction of Mainland China, the PM2.5 level was about 20% higher than average.