Related Information

Background

Objectives

Chairperson and Member of the Working Group

Terms of Reference of the Working Group

Activities

News

Meetings

Reports

Photos and Videos


_____________________________
Pages

WESTPAC Working Groups

Marine Science and Applications

Ocean Observations and Services

Capacity Development

"A dust rain" in Beijing, 2006: 20kg per capita
“Black dust storm” in Minqin, China, April 24, 2010, ref. http://news.qq.com/a/20100426/000334_8.htm

Since 1980s, a variety of studies associated with dust events have been performed, including mineralogy, chemical composition, geologic processes, transport, deposition, optical properties, particle size distributions of globally transported dust and the linkage between dust and atmospheric environment and climate change (Arimoto et al., 2001; Shi et al., 2003 ). The main sources of globally distributed dust are figured out, including the Sahara-Sahel region of Africa, Taklimakan and Gobi deserts of Asian, Australian deserts and Northern America (Zhang et al., 2003). Soil-derived particles account for a large fraction of atmospheric particles, with radii ranging from less than 0.1µm to 100 µm (Arimoto et al., 1997; Prospero et al., 2002). Particles larger than 5 µm are present only in source regions while particles in the size range from 0.1 to 5 µm have a lifetime from hours to weeks, allowing long-range transport over thousands of kilometers from their sources (Arimoto, 2001; Prospero, 2001, 2003). Dry and wet deposition of these particles leads to a large gradient of dust concentrations and deposition fluxes that vary substantially on time scales of ~1 day (Jickells et al., 2005).

There have been a number of investigations in the literature regarding the transport of aerosols from the continents to the ocean (Bergametti et al., 1989; Arimoto et al., 1995; Gong et al., 2003; Zender et al., 2003; Zdanowicz et al., 2006). They reported the existence of Saharan dust even over the remote areas of the Atlantic and Pacific Oceans, and some studies reported that trans-Pacific Asian dust can be often detected in the subarctic and tropical Pacific oceans, especially in the western Pacific Ocean.

Dust sources in East Asia are also the major dust sources on the earth. Asian dust generates at high latitude and high elevation while it is not case for other dust sources. The characteristics of Asian dust in morphology, soil texture, and dust storm activities are unique (Xuan al., 2000; 2002; 2004). Asian dust is driven by the synoptic condition different from others. For example, Asian dust, particularly in the source region of East Asia, frequently occur in spring (Littmann, 1991) while Sahara Desert and most other sources frequently occur in summer (Prospero et al., 2002).

Deserts in Middle Asia, Northwestern China and the boundary area of China and Mongolia are the major source regions of Asian dust. Studies show that dust storm in different extents actually occur in any season including in summer and fall in the proximity to the source area, although the regional outbreak mainly occur in spring.

Although the data and analysis methods used in those studies are different, both the frequency of dust storm (include blowing dust and dust storm) and dust storm days are found to vary greatly year-by-year since 1950’s. There is an evidence to suggest that the frequency and magnitude of Asian dust storms has been on the decline since the late 1970s until recently, has a slight increase in 2000-2002, and 2006-2007(Qian et al., 2002; Ding et al.,2003;Shao et al., 2006; Chen et al., 2007). This is probably a result of the combination of human effort on environment protection and climate variability, but the explanation need more evidences.

The regions affected by the Asian dust storm include not only China and Mongolia but also the downwind Korea, Japan, the Pacific Ocean, the west coast of America, even the subarctic region and Europe (Duce et al., 1980;Husar et al., 2001; Fang et al., 2002;Zdanowicz et al., 2006). The Asian dust storm is obviously a hemispheric scale phenomenon, which has more important impact on the ecosystem in the western Pacific.

Annually, 10 to >102 Tg of soil-derived mineral aerosol are transported from the arid East Asian, contributing to 5%~40% of the global dust release estimated (Zhang et al., 1997;Luo et al.,2003; Ginoux et al., 2004; Tanaka et al., 2006). Asian dust can also deposit large amounts of nutrients (e.g. nitrogen, iron) into the coastal and Pacific Oceans, and impacting surface biological productivity and the air–sea exchange of CO2 associated (Bishop et al., 2002; Yuan.,2006;Zhang et al, 2007). For the subarctic Pacific, an important HNLC (high nitrate low chlorophyll) region in the northern hemisphere, transport and deposition of mineral dust from Asia appears to be the major source of Fe (Duce et al., 1991). Phytoplankton growth in this region has been shown to be stimulated by increasing Fe concentration of the surface waters in the region, but it is still difficult to establish a cause-effect relationship between Asian dust passages and phytoplankton bloom events (Bishop et al., 2002; Yuan et al., 2006). For the subtropical Pacific, typical oligotrophic waters in global ocean, there are some evidences to show dust-driven increases in near surface NO3 concentrations, suggesting that direct atmospheric deposition of both NO3 and Fe (Ditullio and Laws, 1991) and strong wind accompanied by dust storms resulting in nutrient entrainment into the mixed layer from subsurface waters (Hung et al., 2009) were required to stimulate the biota and export flux of particulate organic carbon (POC).

To promote the study on Asian dust and its impact on ocean ecosystem in the western Pacific, a draft scientific plan of ADOES (Asian Dust and Ocean EcoSystem) is proposed in 2008. The goal of ADOES is: To improve the understanding of the deposition flux and bioavailability of Asian dust, and its impact on biogeochemical processes and productivity of marine ecosystem in the western Pacific.

Copyright 2013 © IOC Sub-Commission for the Western Pacific (WESTPAC)