Environmental impacts of three Asian dust events in the northern China and the northwestern Pacific in spring 2021.

In March 2021, China experienced three dust events (Dust-1, 2, 3), especially the first of which was reported as the strongest one in recent ten years. Their environmental impacts have received great attention, demanding comprehensive study to assess such impacts quantitatively. Multiple advanced measurement methods, including satellite, ground-based lidar, online aerosol speciation instrument, and biogeochemical Argo float, were applied to examine and compare the transport paths, optical and chemical properties, and impacts of these three dust events on urban air quality and marine ecosystem. The results showed that Dust-1 exhibited the largest impacts on urban area, increasing PM10 concentration in Beijing, Shuozhou, and Shijiazhuang up to 7525, 3819, and 2992 μg m-3, respectively. However, due to fast movement of the Mongolian low-pressure cyclone, the duration of northwest wind over the land was quite short (e.g., only 10 h in Beijing), which prevented the transport of dust plume to the northwestern Pacific, resulting in limited impact on the ocean. Dust-2 and Dust-3, though weaker in intensity, were transported directly to the sea, and led to a substantial increase in chlorophyll-a concentration (up to near 3 times) in the northwestern Pacific, comparing to climatological value. This indicates that the impacts of dust events on ocean was not necessarily and positively correlated to their impacts on land. Based on the analyses of land-ocean-space integrated observational data and synoptic systems, this study examined how marine ecosystem responded to three significant Asian dust events in spring 2021 and quantitatively assessed the overall impacts of mega dust storms both on land and ocean, which could also provide an interdisciplinary research methodology for future research on strong aerosol emission events such as wildfire and volcanic eruption.