Yanli Lyu

East Asian dust storm in May 2017: observations, modelling and its influence on Asia-Pacific region

A severe dust storm event originated from the Gobi Desert in Central and East Asia during 2–7 May 2017. Based on Moderate Resolution Imaging Spectroradiometer (MODIS) satellite products, hourly environmental monitoring measurements from Chinese cities and East Asian meteorological observation stations, and numerical simulations, we analysed the spatial and temporal characteristics of this dust event as well as its associated impact on the AsiaPacific region. The maximum observed hourly PM10 (particulate matter with an aerodynamic diameter ≤ 10 μm) concentration was above 1000 μg m−3 in Beijing, Tianjin, Shijiazhuang, Baoding, and Langfang and above 2000 μg m−3 in Erdos, Hohhot, Baotou, and Alxa in northern China. This dust event affected over 8.35 million km2, or 87 % of the Chinese mainland, and significantly deteriorated air quality in 316 cities of the 367 cities examined across China. The maximum surface wind speed during the dust storm was 23– 24 m s−1 in the Mongolian Gobi Desert and 20–22 m s−1 in central Inner Mongolia, indicating the potential source regions of this dust event. Lidar-derived vertical dust profiles in Beijing, Seoul, and Tokyo indicated dust aerosols were uplifted to an altitude of 1.5–3.5 km, whereas simulations by the Weather Research and Forecasting with Chemistry (WRFChem) model indicated 20.4 and 5.3 Tg of aeolian dust being deposited respectively across continental Asia and the North Pacific Ocean. According to forward trajectory analysis by the FLEXible PARTicle dispersion (FLEXPART) model, the East Asian dust plume moved across the North Pacific within a week. Dust concentrations decreased from the East Asian continent across the Pacific Ocean from a magnitude of 103 to 10−5 μg m−3, while dust deposition intensity ranged from 104 to 10−1 mg m−2. This dust event was unusual due to its impact on continental China, the Korean Peninsula, Japan, and the North Pacific Ocean. Asian dust storms such as those observed in early May 2017 may lead to wider climate forcing on a global scale.

Blown Sand Disasters in China

Blown sand disasters are caused by sand activity. It can lead to casualties of people and livestock, declining productivity of farmland and pasture, damage to buildings, roads, communication and other facilities, as well as deterioration of air quality (Gao et al. 2000). In northern China, due to the dry and windy climate and large land areas that are covered with sparse vegetation, sand activity is intense and blown sand disasters occur frequently with serious damages. Depending on the severity, sand and dust storm (SDS) weathers can be divided into floating dust, sand-blowing, and sand and dust storm types. Among these, strong and extremely strong sand and dust storms are the main types of SDS weather that causes blown sand disasters (CMA 2006). Sandstorm and dust storm have been a notable natural phenomenon in northern China historically (Zhang 1982). Due to the constantly growing human activities, the coupling effect of land desertification and climatic aridification has been strengthened and thus increases the risk of blown sand disasters. This chapter discusses sand and dust storm and blown sand disasters in northern China, including the spatiotemporal distribution characteristics of sand and dust storms, formation process of blown sand disasters and influences, blown sand disaster risk, and a case of blown sand disasters in China in 2000.

Desertification and Blown Sand Disaster in China

Approximately 331 million ha, one-third of China’s total land, is prone to desertification processes, leading to natural disasters and economic losses. In this study, the situation, tendency, their influences and their risk governance of desertification and blown sand disaster in China were examined using satellite images, field photographs, field data and a literature review. The desiccated areas in Lop Nor and the lower Heihe River fluvial plain covered about 50,000 km and 40,000 km, respectively. In Ejina, about 100 species of vegetation became extinct. The rate of wind erosion in China was between 1,000 tons/km/year and 2,000 tons/km/year. There were 12 sand deserts and sandy lands, occupying a total of 710,000 km. Salinized soils occurred across 99.1 million ha. The two main sand and dust storm-prone areas in China were the Tarim Basin and its surroundings, and the Alxa Plateau and its surroundings. From 1981 to 2007, the annual average frequency of sand and dust storms varied from 1 d to 37 d with a general increase from southeast to northwest. Since 1978, China has implemented a number of ecological construction projects that have reduced desertification from 1999 to 2004 and from 2005 to 2009, and the number of dust and sand storm days from 9.3 d between 1954 and 1959 to 4.4 d between 2000 and 2007. The results could improve understanding of desertification and blown sand disasters in China and provide valuable experiences for global desertification control.