Arctic Oscillation, weather disturbances, and East Asian dust storms

摘要

There is rapidly increasing concern on dust storm activity and its influence as the population and economic significantly grows in East Asia during the recent decades. Dust storm is now regarded as a severe disaster in China, though it has frequently been documented as a natural phenomenon in historical and geological records (e.g. Zhang, 1984; Zhang et al, 1997), as well as a global phenomenon occurs frequently elsewhere, such as in northern Africa and Central Asia (e.g., Littmann, 1991; Goudie and Middleton, 1992). East Asian dust storm activity has experienced evident inter-annual and long-term trends. A predominant feature is the decreasing trends in the number of dust storm days (Zhou 2001). The number of dust storm events also shows a similar and consistent trend (Zhou and Zhang, 2003). A variety factors is suggested to account for the dust storm changes, including (1) atmospheric circulation background changes (Qian et al., 2002; Zhao et al., 2004); (2) Regional climate variables, such as land surface air temperature, precipitation, and gale; (3) teleconnection factors such as ENSO is supposed to, at least partly, play roles in influencing dust storms. Frequent dust storms tend to take place when the La Nina at its peak, through influencing East Asian winter monsoon (Ye et al. 2000; Mu and Li, 1999; Gao et al., 2003). Land surface sensible heat in Tibetan Plateau also may exert influence on middle-high troposphere circulation and consequently influence dust storm weather with an out-of-phase relationship between them (Li et al., 2003); (4) local land cover changes resulted from human activity is often blamed for the genesis and enhancement of dust storms (Ye et al., 2000). Recent decline in dust storm frequency in northern China is found to be in good agreement with the vegetation changes in vegetation health index and vegetation coverage there (Fan, 2003; Zou and Zhai, 2004).