Meteorological Drivers of East Asian dust activity in spring 2001-2022

East Asian dust storms from the Gobi and the Taklamakan Desert occur frequently in spring. Dust aerosols influence climate through effects on radiation and clouds, and impair air quality with impacts on human health. However, large uncertainties in model simulations of dust aerosols persist. An estimation of the relative contributions of different meteorological drivers to dust activities can help to improve the representation of dust storms in models.

Mongolian cyclones, which form East of the Altai-Sayan Mountains, are important for dust-emitting winds in the Gobi Desert. Utilizing an automated detection algorithm of extratropical cyclones and multiple datasets for dust aerosol for 2001–2022, the contribution of Mongolian cyclones to East Asian dust emission and dust optical depth is quantitatively estimated (Mu and Fiedler). The results highlight that springtime dust storms in East Asia are primarily associated with a low-pressure system over Mongolia. Mobile Mongolian cyclones explain almost half of the total spring dust emission amount of the Gobi Desert. The calculated relative contributions of Mongolian cyclones to dust emissions in the Gobi Desert are similar from two different products, despite differences in the physical parameterization schemes for dust emission, number and location of the prescribed potential dust sources, and in the absolute dust emission amount by a factor ten. Dust emissions in the Gobi Desert and dust aerosol optical depth in the region downwind have decreased in the past decades, with Mongolian cyclones contributing to reductions of 10%-18% decade^-1 and 11%--15% decade^-1, respectively. The reduction of dust emissions and dust aerosol optical depth is at least in part explained by weaker and fewer Mongolian cyclones over time. 

Mongolian cyclones may also affect the dust activity in the Taklamakan Desert to the west of the Gobi Desert. The passage of the Mongolian cyclone in mid-March 2021 has led to a cold air intrusion into the Taklamakan Desert. The cold air favored the nighttime near-surface temperature inversion. The stable stratification near the surface allows the development of Nocturnal Low-Level Jets (NLLJs). The breakdown of NLLJs results in a strengthening of near-surface winds, which are sufficiently strong for dust emissions in many parts of the Taklamakan Desert (Mu et al., 2023). The Taklamakan dust was elevated by deep mixing and transported eastwards by prevailing mid-level westerlies, impacting air quality primarily in western China. Ongoing work addresses the link of cyclones and NLLJs in the Taklamakan Desert from the climatological perspective.

References:

Mu, F., Luiz, E.W., Fiedler, S., 2023. On the dynamics and air-quality impact of the exceptional East Asian dust outbreak in mid-March 2021. Atmos. Res. 292, 106846.
Mu, F. and Fiedler, S., in review. How much do atmospheric depressions and Mongolian cyclones contribute to East Asian spring dust activities?