奈曼沙漠化对草地微气象特性影响的研究

为探索沙漠化发生机制，在内蒙古奈曼的流动沙丘，干草地和湿草地进行了微气象观测，并用热量平衡法分析观测数据。观测结果表明，沙漠化发生后，反射率增加，净 辐射减少；而且热量平衡中土壤热通量所占份额增加，潜热通量所占份额减少。干、湿草地的风速廓线在白天和夜间都近于对数分布。而沙丘的风速廓线只在晚上近于对数分布。白天沙丘近地表风速垂直切变较大，从而对沙丘表面产生较强切应力。曳力系数白天低于夜里，沙丘低于干、湿草地。

A Study of the Influence of Desertification on Micrometeorological Characteristics of Grassland at Naiman, Inner Mongolia, China

In order to find the mechanism of desertification in semi-arid areas, the measurement of micrometeorological elements were carried out at a sand dune, a dry grassland and a humid grassland in the desertified area at Naiman, Inner Mongolia, China. The obtained data were analyZed using the energy balance method. The results show that: with progression of the desert, the albedo increases and thus the net radiation decreases; the share of the soil heat in the heat budget increases, and the share of the latent heat decreases. The wind profile over the dry and humid grasslands is nearly logarithmic in the daytime as well as at night. The wind profile above the sand dune is nearly logarithmic only at night. The vertical wind--speed gradient near the sand dune surface is larger in the daytime, which produces stronger shear stress on the surface. The drag coefficient is lower during daytime than at night, and lower at the sand dune than at the dry and humid grasslands.