关键词: 大风日数, 沙尘日数, 时空分布, 变化趋势

Abstract: Based on ground meteorological observational data, and taking the days of instantaneous wind speed ≥17.0 m·s-1 or wind force scale ≥8 and the sand-dust weather days as indexes, the author analyzed the space-time distribution and the changing trend of gale and sand-dust weather in Shanxi. Besides, the causes of sand-dust weather change are discussed from aspects of modern climatic change, general circulation characters and gale frequency change. Main results are as follows: The temporal variations of sand-dust storm, sand-blowing days and gale frequency are synchronous, showing "one-peak and one-vale inner-year mode" with peak in April and vale in month from Aug. to Sep. Variation of dust-floating days shows " two-peak and two-vale inner-year mode" whose principal peak and vale appeare simultaneously with gale, and secondary peak and vale appeare differently on December and February. The peak value and vale value of gale frequency are respectively as 8.39 and 83.3 times of that of sand-dust storm and 2.31 and 18^98 times of that of sand-blowing days. As for spatial distribution, sand-dust storm, sand-blowing days and gale days are more in the north than in the sout of Shanxi, but the distribution of dust-floating days is opposite. Variation in time, the total days of sand-dust storm and dust-blowing weather after early 1900s has decreased by 84.9% and 77.1% of that in 1950s and 1970s respectively. In the years when sand-dust events frequently happened the meridionality of general circulation is much forceful, the Ural pressure ridge is slightly strong, the East Asia great trough lies by west and deepens, but in the less sand-storm events years the case is on the contrary. The changing trend of sandstorm and sand-blowing days had perfect coherence with that of gale, and their linear correlative coefficients differently reach to 0.80 and 0.82. The result indicates that gale is the controlling factor of sand-dust storm and dust-blowing weather days in Shanxi province. Causes for decrease of sand-dust storm and sand-blowing days in Shanxi province during 1957—2007 mainly lie in wind force weakness due to frequency decrease and force weakness of going southward cold air from high latitude.

Key words: gale days, sand-dust days, space-time distribution, changing trend