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Recent frequent dust events and their relation to surface wind in East Asia Yasunori Kurosaki1,2 and Masao Mikami1 Received

6 March 2003;

revised

24 May 2003;

accepted

9 June 2003;

published

19 July 2003.

[1] A remarkable increase in dust outbreaks has occurred in the eastern part of the Asian Continent over the last three years (2000C2002) compared with the previous seven years (1993C1999). This finding corresponds well with the annual change of Kosa (i.e., yellow sand) events for the same period in Japan. Dust outbreaks occurred in limited regions around southern Mongolia, the Badain Jaran Desert, and the western Loess Plateau from 1993C1999. However, the area of frequent dust outbreaks expanded extensively to the east, and dust outbreaks also frequently occurred in regions around the North China Plain, northeastern China, and the Korean Peninsula in

2000 C 2002. Good correspondence was found between the surface wind and dust outbreaks in year-to-year variations and in spatial distributions. This indicates that frequent strong winds are the primary cause of the recurrent dust outbreaks in the last three years. INDEX TERMS:

0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801);

3309 Meteorology and Atmospheric Dynamics: Climatology (1620);

3307 Meteorology and Atmospheric Dynamics: Boundary layer processes;

3322 Meteorology and Atmospheric Dynamics: Land/ atmosphere interactions;

9320 Information Related to Geographic Region: Asia. Citation: Kurosaki, Y., and M. Mikami, Recent frequent dust events and their relation to surface wind in East Asia, Geophys. Res. Lett., 30(14), 1736, doi:10.1029/2003GL017261, 2003. 1. Introduction [2] Mineral dust aerosol particles give impacts on the global climate via their radiative forcing effects and cloud microphysical processes. Dust storms, which generate min- eral dust, are disasters, affecting human health, traffic conditions, agriculture, and other aspects of daily life. [3] The long-term variations of dust event frequencies have exhibited a negative trend over the last

40 years in China [Qian et al., 2002;

Parungo et al., 1994;

Sun et al., 2000;

Yoshino, 2002]. However, East Asian dust events have become uncommonly active in recent years. A report for the press of Japan Meteorological Agency (http:// www.kishou.go.jp/press/0204/15a/kosa.pdf) stated that it is remarkable that Kosa (i.e., yellow sand) events were fre- quently observed in Japan in the last three years (2000C 2002) (Figure 1). Dust phenomena also frequently occurred after

2000 in Korea. Dust phenomena were observed over

10 days in Seoul City in every year after 2000, although the average number of days of dust phenomena was 5.2 from 1915C2002 [Chun et al., 2002;

Chun et al., 2001]. In addition, large-scale dust events that transported mineral dust particles across the Pacific Ocean occurred in

1998 and

2001 [e.g., Husar et al., 2001]. The reasons for the recent trend of active dust events and any relation to the dust outbreaks in East Asia have not been clarified. [4] Aeolian dust is usually generated by strong surface wind on arid and/or semi-arid regions with low vegetation cover. East Asian cyclone activity is strong around the Gobi Desert in spring [Chen et al., 1991], and the Gobi Desert is a major dust source region in East Asia. [5] The relationship between dust outbreaks and strong winds was investigated in this study to clarify the recent active dust events in East Asia. We conducted statistical analyses of dust outbreaks and strong surface winds in East Asia during the past ten years (1993C2002), using the present weather code and the surface wind velocity obtained from the SYNOP report [WMO, 1974]. 2. Data and Methods [6] The data used in this study were the present weather code and surface wind velocity at a