民勤沙尘源区近地面降尘特征研究

借助近地面沙尘暴监测系统进行沙尘暴监测，分析民勤沙尘源区近地面降尘分布特征.结果表明:民勤降尘量与沙尘天气发生频率密切相关，春季3，4月沙尘高发期月降尘量分别为9.0和9.5 mg/cm2.降尘随距地面高度的增加而减小，最大降尘出现在近地面1 m处，月降尘量为9.7 mg/cm2；降尘受下垫面条件影响较大，从荒漠区到绿洲边缘，风速减弱4.11%，总降尘量由25.0 mg/cm2减少到20.6 mg/cm2；绿洲内部受防护林作用，风速减弱30.45%，总降尘量增到24.6 mg/cm2，最大降尘量提高到近地面9 m处，与绿洲防护林冠层平均高度相吻合.风速对近地面20m内的降尘影响明显，平均降尘量2.5 mg/cm2.距地面9 m的高度范围内，降尘随持续时间变化迅速增加，降尘增量可达3.1 mg/cm2. 

Study on Character of Dustfull near the Ground in Minqin Dust Source Regions

A near ground sandstorm observation system was used to monitor the sandstorms and analyze the character of dustfall near the ground in Minqin dust source regions. The results show that the dustfall in Minqin has the same frequency as dust events, and the monthly dustfall intensity is 9.0 and 9.5 mg/cm2 respectively in March and April which are the two months with highest occurrences of dust events. The quantity of dustfall decreases with the height, and the maxim dustfall appears at 1 m near ground, with the monthly value of 9.7 mg/cm2. The condition of underlying surface significantly affects the dustfall, from the desert to the oasis edge, the wind speed weakens by 4.11% and the total dustfall decreases from 25.0　mg/cm2 to 20.6　mg/cm2. Within the oasis, thewind speed weakens by 30.45%, the total dustfall increases to 24.6 mg/cm2 due to protection of defense forest, and maximum dustfall enhances to the height of 9 m, inosculating with the height of average coronal layer of oasis defense forest. It is evident that the wind speed affects the dustfall near the surface of 20 m heights, with the average dustfall of 2.5 mg/cm2. The dustfall rapidly increases with duration time of dust and sand, and the increment of dustfall can reach 3.1　mg/cm2 within the height of 9　m.