Inrtoduction of Dust Storm |
East Asian dust storm events are mostly originated from Mongolia and deserts in the northwestern China, covering a total area of 600,000 square kilometers. For those areas, the annual rainfall is less than 400mm, and the season distribution is uneven. Loose soil, dry and non-vegetated surface are often associated. Dust storm events occur mostly from March to May, accounting for 60% of the whole year. After the formation of large-scale dust storms, the air will contain a lot of dust particles and obscure the sunshine, even with zero visibility. so a powerful sandstorm is also known as Black Blizzards. After the dust The larger particles may settle on the adjacent areaswhile the smaller particles may rise to the altitude of 850-700 hPa, equivalent to 1500 meters to 3000 meters, and then being delivered by the westerly winds to the East. A portion of the dust particles are dispersed or diluted during transmission, resulting in lower concentration with longer distance. Dust from the northwestern China can be transported as far as Korea, Japan, North Pacific and Hawaii (10,000 km away). Hong Kong, Taiwan and Philippines at the South are also affected. There were dust storm events recorded in Korea’s history as early as 479 AD and 700 AD. A number of studies have shown that sand and dust from the desert regions are major sources of suspended particles, and those from the Sahara desert have accounted for 25% of the particulate matter in the atmosphere (Zhou and Yu, 1990). Therefore, the influence brought by deserts in the northwestern China should not be underestimated. (Cited and edited from: Taiwan Environmental Protection Administration in China dust monitoring network http://taqm.epa.gov.tw/dust/zh-tw/default.aspx)
The negative impact caused by dust storminclude the deterioration of air quality and reduced visibility. Due to the rising trends of the East Asian dust storm events in terms of their frequency, scale and magnitude, the influences brought to the public are becoming more serious. The increase of suspended particles in the air, likely to cause allergic rhinitis, coughing, wheezing, eye irritation, skin irritation, itching and other symptoms. According to the study by EPD, a prevalence of respiratory symptoms, an increase of sick leave students and rising clinic rate of the general public are the most obvious impact on human health.
The huge amount of the suspended particles lead to deterioration of air quality. Therefore, those who have respiratory or cardiovascular diseases, especially the elderly and children, should avoid any outdoor activities during sand and dust weather. Face masks and goggles are effective to prevent direct contact if outdoor activities are necessary.
(The above quoted and edited from: Sharon Cai Liang Hong Kong Observatory of the March 21, 2010 sandstorm affecting Hong Kong case studies)
