East Asia dust storms in spring 2021: Transport mechanisms and impacts on China

Abstract

In spring 2021, several strong dust export processes crossed over East Asia, including the combined transport of Mongolia Gobi and Inner Mongolia dust. Based on CAMS forecast systems and satellite sensors, we analyzed the transport mechanisms and impact on China. Our case studies illustrate that in all 4 dust storms, the initial phase of transport was strongly confined by a low-level Mongolian cyclone facilitated by a deep cold-core upper trough. Using a methodology based on MODIS Deep Blue AOD data enables us to estimate the dust optical depth (DOD) and the impact of dust plumes on different areas in China. The result shows that North China was the most affected area in all cases, second only to the source region, with a mean observed DOD >0.8 and depolarization ratio > 0.2. The vertical distribution of the aerosol frequency of occurrence (FoO) was yielded using the CALIOP aerosol classification result. Dust storms were the dominant factor within 6 km (peaked at 2–3 km), while a significant amount of transported smoke aerosols dominated the upper troposphere. Even in dust storms, anthropogenic aerosols still occupied a high proportion of China's atmosphere, especially in South China, indicating the great contribution of human activities. As a subdominant aerosol type, polluted dust showed a profile similar to that of polluted continental aerosols, with peak heights generally lower than that of pure dust, at approximately 1–2 km. The development of cyclone/anticyclone activities was mostly modulated by the atmospheric dynamic background. By discussing the climatic index related to dust storm occurrence in East Asia, we found that the high-frequency years in the 21st century have a satisfactory correspondence with the negative phase of the Pacific Decadal Oscillation (PDO) and the positive phase of the Southern Oscillation Index (SOI). These findings may have positive significance for dust forecasting in East Asia in the future.