Quantitative classification of northeast Asian dust events

In this paper, we introduce a quantitative classification of dust events on the basis of dust, PM 10 concentration, and wind speed for northeast Asia. The empirical relationship between visibility and PM 10 concentration is established by regression of visibility and PM 10 concentration that were taken every 5 min at 11 sites in the spring of 2004 and 2005. The empirical relationship is then applied to establish the spatial and temporal patterns of dust and PM 10 concentrations by using the visibility data obtained from 1680 meteorological stations in the spring seasons of 2000–2005. The results showed that the PM 10 concentration estimated from visibility is consistent with the observed PM 10 concentration. The classification standard of dust events used by different countries did not show consistent results in northeast Asia. It is recommended that dust events in northeast Asia be classified as follows: (1) severe dust storm, ρ TSP ≥ 6000 μ g m −3 , ρ PM10 ≥ 5000 μ g m −3 , and v ≥ 10 m s −1 ; (2) dust storm, 3000 μ g m −3 ≤ ρ TSP < 6000 μ g m −3 , 3000 μ g m −3 ≤ ρ PM10 < 5000 μ g m −3 , and 10 m s −1 ≤ v < 15 m s −1 ; (3) blowing dust, 900 μ g m −3 ≤ ρ TSP < 1500 μ g m −3 , 200 μ g m −3 ≤ ρ PM10 < 600 μ g m −3 , and 5 m s −1 ≤ v < 10 m s −1 ; and (4) floating dust, 750 μ g m −3 ≤ ρ TSP < 1200 μ g m −3 , 200 μ g m −3 ≤ ρ PM10 < 400 μ g m −3 , and 2 m s −1 ≤ v < 5 m s −1 .