Abstract
Spring dust frequency in northeast Asia has been investigated using various approaches to understand the mechanisms of dust emission and transport. However, little attention has been paid to the linkage between dust activity and the Siberian High (SH), particularly when the SH pressure system is highly variable. In this study, we characterize the possible physical mechanisms of dust emission and transport associated with the Siberian High Intensity (SHI) and Siberian High Position Index (SHPI) in March using 18 years of ground-based observations and reanalysis data. We found that when the SHI was strong and the SH’s center was farther east (“Strong–East period”), surface and atmospheric temperatures were cooler than when the SHI was weak and the SH’s center was farther west (“Weak-West period”), due to anomalous anticyclonic pressure and strong easterlies. As a result, a reduction in the meridional temperature gradient in the lower atmosphere suppressed dust emission and transport, due to stagnant atmospheric conditions. This anomalous anticyclonic pressure in the Strong-East case seems to reduce the development of extratropical cyclones (ETC) in northeast Asia, leading to a less effective dust transport. A case study with composite analysis also showed a similar physical mechanism: stagnant air accompanying weakened westerlies in the Strong-East period suppressed dust transport to South Korea. Our findings reveal that the intensity and position of the SH can be utilized to identify spring transboundary air pollutants in northeast Asia.
Highlights
Yellow sand, or Hwang-sa in Korean, is a frequent meteorological phenomenon in which sand dust is suspended in the air and gradually falls to the surface [1]
We demonstrate a possible physical mechanism to explain differences in the dust occurrence frequency (DOF), dust event frequency (DEF), extratropical cyclones (ETC) frequency, and intense ETC frequency associated with synoptic meteorological characteristics over the dust source regions and South Korea
Compared to the 18-year meteorological patterns, the area affected by high mean sea level pressure (MSLP) (>1022 hPa) for the Strong-East period occupied over the full width of the Siberian High Position Index (SHPI) calculation domain (Figure 4b)
Summary
Hwang-sa in Korean, is a frequent meteorological phenomenon in which sand dust is suspended in the air and gradually falls to the surface [1]. Dust storms move to eastern China, the Korean Peninsula, and Japan with strong northwesterly winds induced by atmospheric baroclinic instability in the lower atmosphere [1,8,9,10,11]. Dust aerosols contain both particulate matters (PM) with an aerodynamic diameter smaller than 10 μm (PM10) and smaller than 2.5 μm (PM2.5) [12,13]. In South Korea, the yellow dust events are observed in all seasons except summer. Over the past 100 years, approximately 86% of the dust events observed in Seoul, South Korea, occurred in spring [21]
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