A transient simulation of precession-scale spring dust activity over northern China and its relation to mid-latitude atmospheric circulation

Abstract

Dust aerosol plays an important role in energy and water cycles of the earth system across multiple spatial and temporal scales, and it is also a key factor in determining air quality in arid and semi-arid areas of Asia. Spring is the season of peak dust activity (i.e. emission, transport, and sedimentation) in Asia. However, on the Earth's orbit scale, spring dust activity in northern China (NC) and its relationship with atmospheric circulation have seldom been investigated. We present the results of an analysis of the evolution characteristic on the astronomical timescale, and dynamic mechanism of spring dust activity in NC, based on a transient numerical simulation over the past 150 kyr spanning multiple precessional cycles. We found that within the precessional band, spring dust transport is in-phase with insolation, the upper Westerly Jet on the north (nWJ) of the Tibetan Plateau (TP), surface wind, and heating of the TP; whereas it is out-of-phase with Siberian high (SH), atmospheric precipitation, and soil water. During the high-insolation stage, the nWJ is strengthened by the thermal forcing of the TP, which causes a northward shift of the location of the Westerly Jet, so that dust activity is enhanced by the propagation of upper-level waves. Meanwhile, during the high-insolation stage, the instability of the lower atmosphere is increased due to the strengthening of the northerly wind associated with the weakening of the SH and surface warming, together with their higher interaction, with the nWJ giving rise to dust mobilization in the Asian arid and semi-arid source areas, and vice versa. Rainfall and soil moisture have little influence on the dust cycle on the orbital scale, although modern observations show they have an important inhibitory effect on dust emission.