火星表面风沙物理过程及沙尘暴的起动风速

Physics of Wind-blown Sand and the Threshold Wind Speed of Dust Storms on Mars

通过建立风吹动地表沙粒运动的模型并根据大气湍流边界层风速廓线规律,计算了火星上沙尘暴的起动风速和沙尘暴发生时空中悬浮沙尘粒径的大小,并对沙粒从地面跳起进入气流的方式进行了验证.发现当大气为中性层结时,火星沙尘暴的起动需要离地面2 m高处的风速达到28.7 m·s^(-1).在起动临界风速下,地表沙粒需要滚动一个粒径的距离才能跳起,沙尘暴发生后,火星大气中悬浮沙尘的粒径小于30μm.

The planet Mars is most closely related to Earth in its size and character. From the comparative planetology point of view, what happens on Mars is of importance to our human being on the Earth. There exist dust storms on both Earth and Mars. The dust storm on Mars is different from that on Earth in its scale. However, in some aspects, they are similar on these two planets, like the mechanism for the generation of dust storm. In this paper, a model of wind-blown sand at the surface of sanded ground is constructed, and the threshold wind speed for dust storms to start on Mars is calculated based on the wind profile of atmospheric turbulent boundary layer. It is concluded that the wind speed of 28.Tm.s-1 at 2 m height is needed for a dust storm to start on Mars, and the suspended dust particles＇ diameter is less than 30 μm when wind speed is at the threshold value. It is also found that sands need to roll a distance of one particle＇s diameter before saltation.