Effect of frozen ground on dust outbreaks in spring on the eastern Mongolian Plateau

Very little is known about the effect of frozen ground on dust outbreaks in East Asia. We therefore examined the influence of springtime frozen ground and thawed ground and non-frozen ground before the first rainfall event on dust outbreaks on the eastern Mongolian Plateau, the principal contributor to the long-range transport of dust to the North Pacific, during the springs of 2000–2007. Radar backscatter data, MODIS data and meteorological records were used to investigate the relationship between frozen ground and dust events. We found that dust events occurred in association with strong wind on frozen ground (15.7 m/s) and thawed ground (12.6 m/s), compared with non-frozen ground (10.1 m/s). The number of dust events that occurred before the thaw correlated positively (R2 = 0.82, P < 0.01) with the proportion of non-frozen ground. The number of dust events after the thaw, when water content was high, correlated negatively (R2 = 0.88, P < 0.01) with the proportion of frozen ground. Our results indicate that dust outbreaks in our study area in spring are fewer in years when greater areas of ground are frozen during winter.