Over the study period, a total of 8451 severe spring dust storms were observed at the 23 ground stations, with an average of 156.5 severe spring dust storms per year.
Based on the ground observations of dust storm events in central Inner Mongolia, we demonstrated a significant declining trend of severe spring dust storms from 1954 to 2007.
At the decadal scale, the 1960s experienced the highest number of severe spring dust storms (annual average 232.4), and severe spring dust storm occurrence was most restrained in the 1990s (annual average 64.1) (Fig. 3).
The maximum number of severe spring dust storms (566) was recorded in 1966, and the lowest number was observed in 1997 (Fig. 3).
A significant (p < 0.01) linearly decreasing trend of annual spring dust storms indicates a decrease of 2.99 severe spring dust storm events per year from 1954 to 2007.
In retrospect, even the rapid progressions from uncomplicated influenza infections to fatal pneumonia, a hallmark of the 1918 1919 fall and winter waves, had been noted in the relatively few severe spring wave cases.
