hide
Free keywords:
-
Abstract:
Although the frequency and intensity of dust storm event (DSE) have decreased in northern China in recent years, its occurrence and impacts continue with a more complex formation mechanism under the background of climate change. The results of this study suggest that 2 days prior to the outbreak of the DSE (“Day -2”), the convergence of transient-momentum transport is beneficial for increasing the wind speed to become a jet stream (JS) in the upper level above South Xinjiang. Then, until “Day 0”, the wind speed in the mid-high troposphere remains as a JS, with the largest value on “Day -1”. Through downward upper-level momentum, the lower-level wind increases to a maximum value on “Day 0”. Additionally, the direct influence of transient-heat transport convergence and the indirect influence of transient-momentum transport divergence are helpful for the establishment of the Ural ridge under the negative phase of Eurasian (EU) teleconnection pattern, reinforcing the Siberian Highs (SH) and leading to low-level gales. Consistent high winds at the low-high levels and obvious vertical motion (descending from “Day -3” to “Day -1” and ascending from “Day 0” to “Day +2”) result in dust emissions and transport. Thus, the dust column mass density (CMD) begins to concentrate in South Xinjiang on “Day -2” and achieves the strongest on “Day 0”. Although the influence of the transient eddy and the wind speed decrease after the DSE outbreak, atmospheric circulation is also helpful for dust to expand to adjust and downstream regions over the following 4 days.
