内蒙古中西部地区土壤水分对沙尘暴的贡献

THE CONTRIBUTION OF SOIL MOISTURE TO DUST STORM IN WESTERN AND CENTRAL INNER MONGOLIA, CHINA

以2001年4月至2002年6月内蒙中部地区逐时观测的土壤水分资料为基础,论证了该区日土壤水分和日平均风速的变化规律,统计分析了日平均风速与土壤水分对沙尘暴的成生综合贡献。得出的主要结论是:①该地区沙尘暴发生时日平均风速的最小值是3.5m/s。如果日平均风速大于8.0m/s,预示着有沙尘暴的发生。②在平均风速大于3.5m/s的条件下,观测样本中18.4%日数发生沙尘暴,而81.6%日数没有发生。说明大风的天气条件不应当被视其为沙尘暴的唯一重要的因子。③在同一地点、同样的风力条件下,在沙尘暴发生时,日平均风速与日平均土壤水分呈明显的反相关变化;而它们的反相关关系不明显时,沙尘暴就很少发生。

To recuperate the shortage of soil moisture, based on hourly soil moisture date observed from April 2001 to June 2003 in western and central Inner Mongolia of China, the change regulation of daily mean soil moisture and daily mean wind speed and their integrative contributions are analyzed in the paper. Then rationality of the statistic result is discussed, from which some interesting results can be drawn as follows: (1)The minimum value of daily mean wind speed for dust storm emission is 3.5m/s, and dust storm will occur when the wind speed over 8m/s in this area. (2)There are 18.4% of dust storms that occurred and 81.6% of non-dust storms that occurred in the total data collected when the wind speed was more than 3.5m/s. It indicated that dynamical factor with daily mean wind speed is not a most important one in the factors of dust storm emission. (3)If only soil moisture and wind speed are consider, when there is a inverse relation between daily mean soil moisture and daily mean wind speed, dust storm would occurred (r= -0.674). Otherwise, if their relation were not shown as this inverse, dust storm would not occur. The formation and development of dust storm is an integrative result of soil moisture and wind speed. Continuous data of soil moisture would be an avail index to study dust storm for showing the humid status of soil directly and for scaling the status of vegetation cover indirectly.