A composite comparative study of the dust events in Taipei and Beijing

The purpose of this study was to identify predictors of dust events. A longitudinal study of dust events that occurred in Taipei and Beijing from 2000 to 2002 was investigated. The events were separated into two groups. Group 1 was the dust events, which affected Beijing, and Group 2 was dust events, which affected Taipei. The separation of dust events by the position and extension of the polar continental high was determined. Composite analysis of geopotential height, 850 hPa vorticity and principal components (PC) were then carried out for these two categories. Comparisons of the East Asian main trough distributions, for high-low and negative-positive vorticity demonstrated differences between both of categories. PC analysis revealed that both geopotential height and wind field, for the first two principal components (PC1 and PC2) of Group 1 and Group 2 were also quite different and that the total variance ratio was greater than 90%. The results indicated that the position of the polar high in both cases was similar. The extension of the high that influenced Beijing however covered an area to the north of the Yellow River and that which influenced Taipei, covered an area to the south of the Yellow River. The results also indicated that the trough (PCI) and the cyclonic circulation (PC2) were stronger in Group 2 than Group 1.