民勤近地面沙尘暴气溶胶浓度变化特征初探

Seasonal variations of sandstorm-aerosol concentration near the ground surface around Minqin

借助近地面沙尘暴监测系统对民勤沙尘源区不同沙尘天气的气溶胶浓度进行了监测,初步分析了民勤近地面沙尘暴气溶胶浓度的变化特征.结果表明:沙尘暴气溶胶浓度春季最高,为14.61mg·m-3;夏季逐渐降低,为12.49mg·m-3;秋季无沙尘暴出现,气溶胶浓度最小;冬季趋于回升,可达9.82mg·m-3,沙尘暴气溶胶浓度季节变化与沙尘暴发生频率相一致.不同沙尘天气条件下沙尘气溶胶浓度表现为强沙尘暴最大,为18.80mg·m-3;中沙尘暴次之,为13.56mg·m-3;扬沙浮沉天气较小,只有3.07mg·m-3.随着沙漠向绿洲的过渡,沙尘暴气溶胶浓度明显降低,沙漠、绿洲边缘、绿洲3个下垫面条件下沙尘暴气溶胶浓度依次为21.07mg·m-3、12.09mg·m-3、6.49mg·m-3.沙尘暴气溶胶浓度随观测高度变化遵循幂函数规律,浓度梯度变幅表现为沙尘暴高发季节大于低峰季节,沙尘暴天气大于扬沙浮尘天气,沙漠下垫面大于绿洲下垫面;不同下垫面条件下沙尘暴气溶胶浓度在41m高度处趋于一致,表明沙尘源区的沙尘浓度在约40m范围内受地面影响较为显著.

In order to continuously monitor the sand-dust aerosol concentration in Minqin, a dust source area in China, a monitoring system was set up in 2005. The characteristics of the sandstorm-aerosol concentrations near the surface were determined from January to December 2006. The results showed that the concentration of aerosols in spring was the highest with an average value of 14.61 mg·m^-3, It reduced gradually to 12.49 mg·m^- 3 in summer. There was no sandstorm in fall and the average concentration was 9.82 mg·m^-3 in winter. The sandstorm-aerosol concentration increased proportionally with the sandstorm intensity： the average concentration for strong, middle, and weaker sandstorms was 18.80, 13.56, and 3.07 mg·m^-3 respectively. The sandstorm-aerosols concentration dropped sharply from desert to oasis and the corresponding concentrations were 21.07, 12.09, and 6.49 mg·m^-3 in desert, at the edge of desert and oasis, and in oasis, respectively. Regardless of the type of ground cover, sandstorm-aerosol concentration reduced in power function with height. The range of the sandstorm-aerosol concentrations in the high-frequency season was larger than that in the low-frequency season. The sandstorm-aerosol concentrations were almost the same above a height of 41 m, regardless of the ground cover, indicating that the effects of different ground cover were only apparent to a height of 40 m in the Minqin area.