Dust transport · Northern China and Mongolia
Beijing's worst sandstorm in a decade
On the morning of 15 March 2021 Beijing turned yellow-brown. A deep cyclone over Mongolia had whipped up the Gobi desert, and its cold north-westerly wind swept the dust over northern China within a day. Visibility in the capital dropped to a few hundred metres, hundreds of flights were cancelled and China's weather service called it the strongest sandstorm in ten years.
14–16 March 2021 · Beijing, northern China, Mongolia · CAMS, MERRA-2, ERA5
0.58
Dust optical depth, 15 Mar
CAMS, nearest grid point to Beijing; about four times the March mean of 0.15.
What happened
The storm began over southern Mongolia on 14 March, where it killed several people and left hundreds missing in the herding country of the Gobi.N1 By dawn on 15 March the dust had reached Beijing. The sun became a pale disc; ground stations reported PM10 above 8,000 µg m⁻³ for some hours.N1
Measurements over northern China showed record-breaking dust loading, and a second storm followed at the end of the month.S1
A cyclone over the Gobi
Spring dust storms in East Asia need a strong wind over bare, dry ground. In March 2021 the Gobi had had a warm winter with little snow, and on 14 March a cyclone deepened rapidly over Mongolia. Behind its cold front, a gale of 20 m s⁻¹ and more swept south-east across the desert, lifting the dust and driving it towards the North China Plain.S1
Across a continent
The dust maps show the plume leave the Gobi, wrap round the cyclone and reach the sea within two days. Further west, the Taklamakan and the deserts of Central Asia were dusty at the same time.
What a reanalysis sees, and what it misses
CAMS and NASA's MERRA-2 both place the plume over Beijing on 15 March. Yet near the ground the CAMS PM2.5 for Beijing hardly rises above its usual level of about 250 µg m⁻³, while stations measured a daily PM10 of 7,058 µg m⁻³.S1
The difference is size. Desert dust is mostly coarse, larger than 2.5 micrometres, so it counts towards PM10 but little towards PM2.5. And a reanalysis grid cell of 80 km averages a sharp dust front over a wide area. For dust storms the column amount and the maps are the reanalyses' strength; the street-level peak is the stations'.
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References
News
- N1NPR. Desert dust sweeps into Beijing, causing China's worst sandstorm in 10 years. 15 March 2021.The scene in Beijing, cancelled flights and the deaths in Mongolia.
Studies and guidelines
- S1Gui, K., et al. (2022). Record-breaking dust loading during two mega dust storm events over northern China in March 2021: aerosol optical and radiative properties and meteorological drivers. Atmospheric Chemistry and Physics, 22, 7905–7932.Record dust loading in March 2021, the measured PM10 and the meteorology behind the storms.