沙尘天气过程沙地下垫面沙尘通量的获取与分析研究

EXPERIMENT ON DUST FLUX DURING DUST STORMPERIODS OVER SAND DESERT AREA

中文关键词:  湍流输送，沙尘浓度通量，临界摩擦速度，沙尘暴，沙地.

英文关键词:Turbulent transfer,Dust concentration flux,Threshold friction velocity,Dust storm,Sand area.

中文摘要:

      利用浑善达克沙地地区2004年春季沙尘暴和微气象学加强观测实验资料，计算了浑善达克沙地地区不同沙尘天气条件下湍流交换系数、湍流动量通量和感热通量、沙尘浓度通量；研究了沙尘暴过程中湍流作用、沙尘输送特征及起沙条件。结果显示：浑善达克沙地地区非沙尘天气白天近地层热力湍流作用强于动力湍流，湍流交换以感热交换为主；沙尘天气过程中，近地面层湍流动力作用明显增加，湍流动量和感热交换都对湍流输送有主要贡献，感热通量数值有不同程度的降低。较强沙尘暴天气过程中动力湍流强于热力湍流。随着沙尘天气经历起沙、平衡、沉降的演变过程，沙尘通量数值呈现由正值为主，过渡到向上和向下数值相当、向下数值比例增加。非沙尘天气、扬沙天气和沙尘暴天气过程的沙尘通量值范围分别是±5 μg/(m２?s)、±30μg/(m２?s)和-200—300 μg/(m２?s)之间。浑善达克沙地地区，非沙尘天气也存在一定量的沙尘输送，但数值较小。浑善达克沙地地区沙尘通量与摩擦速度的三次方成正比，为F=Cu 3*。临界起沙风速和临界摩擦速度分别约为6 m/s和0.4 m/s。

英文摘要:

      Based on dust concentration and micrometeorological data obtained during the IOP (Intensive Observation Period) of dust storm over Hunshandake desert area during the spring of 2004, the turbulent exchange coefficients, turbulent fluxes of momentum, heat and dust concentration were calculated. The characteristics of turbulence and dust transport, as well as the dust emission conditions were investigated. The results show that the turbulent exchange of heat is dominant during daytime of non-dusty days over Hunshandake desert area. During dust events, dynamic turbulence increases obviously, the turbulent exchanges of momentum and sensible heat are both important in the surface layer and the sensible heat flux is reduced by different degrees. During the intense dust storm event, the dynamic turbulence even exceeds the thermodynamic turbulence. During dust events, the value of dust flux gradually varies from positive to negative, which indicates the time evolvement of dust storm process. The range of dust flux are ±5 μg/(m2?s), ±30 μg/(m2?s) and -200-300 μg/(m2?s) during non dusty days, blowing dust and dust storm event, respectively. Smaller value of dust flux can be observed during non-dusty days over Hunshandake desert area. The dust emission flux is approximately proportional to the third power of friction velocity over Hunshandake desert area. The threshold values of wind speed and friction velocity are found to be about 6 and 0.4 m/s, respectively.