河套地区春季扬沙天气影响因子的初步研究

通过对河套地区扬沙日数、冷空气活动及固定地段土壤湿度的研究 ,探讨了冷空气活动和土壤湿度对河套地区春季扬沙天气频次的影响。结果表明 ,春季大范围的冷空气活动提供了重要的扰动能量 ;同时 ,强冷空气活动较大的风速 ,为扬沙天气的出现提供了动力条件 ;土壤湿度偏小、土壤干燥疏松也是河套地区扬沙频繁发生的重要原因

PRELIMINARY RESEARCH ON EFFECT FACTORS OF BLOWING-SAND WEATHER IN SPRING IN MID-REACHES OF THE HUANGHE RIVER

Study is undertaken of cold air activities and soil moistures effected on the during blowing sand frequency (referred as BSF hereinafter) in terms of nationwide blowing sand frequency during 1961-2001, 61 stations soil moisture during 1980-2001, 14:00 (BT) wind speed of 27 stations in Mid Reaches of the Huanghe River during 1961-2000, nationwide 600 stations daily temperature during 1960-2000, cold air activities (referred as CAA hereinafter) which affected the north China in spring during 1961-2000. Evidence shows that the cold air activities make for outbreaks of blowing sand in spring, and also lower soil moistures result in outbreaks of blowing sand. Mid reaches of the Huanghe River(referred as MRHR hereinafter) locate in the northwest route of cold air outbreaks, the outbreaks along this route cause dust storms in spring frequently. Results suggest that lower temperature, higher BSF in spring, i.e., air temperature is one of factors in favor of the blowing sand outbreaks. Yanchi is one station in the target region, its meteorological elements are in highly relationship with the other target stations. In spring, 59 strong cold air activities in north China result in 51 blowing sand outbreaks in Yanchi. Curves of BSF of MRHR and CAA in the north China indicate that the former with high amplitude has the same tendency of CAA, less CAA during 1980s and 1990s is one cause in decrease of BSF in spring. High wind speed is one signature of CAA, which mainly contributes to blowing sand outbreaks.It is well known that the land surface is much important to blowing sand outbreaks. MRHR belongs to mid latitude arid/semi arid area, lower soil moisture in spring due to the less precipitation and less vegetation. Outcome indicates that higher BSF is in relation with the lower moisture, as well as the thicker dry soil depth which is in favor of blowing sand outbreaks. In general, frequent cold air activities and lower soil moisture in spring exert notable impacts on high blowing sand frequency in MRHR.