[ABSTRACT] A study on dust storms observed over the territory of Mongolia from January to May in 2004 was carried out. Asian regional and local weather maps at surface and 500-hPa level, and NOAA satellite images were used for the study. The study focused on formation, intensity and movement of dust events originated in Mongolian Gobi Desert area. Atmospheric circulation factors causing formation of dust events are reviewed. During the spring, there were 10 cases of strong dust events and 6 moderate or weak dust events in Mongolia. About 6 of them arrived at and Japan via NE China and the Korean Peninsular. Favourable and unfavourable conditions including winter and spring snowfall for the formation of intense dust storms were studied. Snowfall amount was 1- 12 mm over the Gobi Desert area from January to February, and there was no snowfall over the some areas of the Gobi Desert in those months. Monthly precipitation amount in January and February fluctuated around the climate normal between 1961 and 1990, and less than that. March and April of 2004 were the driest months in Mongolia including the Gobi Desert areas. Monthly precipitation amounts were about 0-5 mm over the most areas of Mongolia in those months. Monthly precipitation amounts were less than the climate normal over the Gobi Desert area in Mongolia in the period from March to May. Soil wet was small in winter and spring, and it was favourable for the formation of dust storms in those periods. NOAA satellite images discover dust clouds over NE Asia in spring.
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