Dust storms and haboobs
Dust storms and haboobs
复制标题
沙尘暴和哈布暴
作者：
Marsham J
沙尘暴在世界干旱地区和沙漠中最为常见，但也可能在任何地方形成，只要强风联合收割机与沉积物结合，沉积物就很容易被抬升到空中。灰尘通常是由一个称为“跳跃”的过程产生的：风速超过阈值（通常约为6至11米/秒）的风夹带较大的颗粒（0.1至1毫米），这些颗粒在表面反弹。这些颗粒本身太重，无法被高高地提升到空气中，但当它们撞击土壤时释放的能量可以克服束缚力，允许较小的颗粒（通常为0.1至50微米）被排放并夹带到大气中。沙尘气溶胶通常是石英、粘土（如高岭石、伊利石）、方解石、石膏和氧化铁的外部混合物。颗粒通常是非球形和片状的。沙尘扬起的理想条件是强风、很少或没有植被以及干燥的沉积物表面。排放率通常被认为是摩擦速度的三次函数，在对应于10米风速约为6至11米/秒的阈值以下没有排放。因此，排放是一个高度非线性的响应，仅取决于相对罕见的高风速事件，使其成为一个挑战模型。主要的灰尘来源包括干涸的湖床（例如撒哈拉南部的Bodélé凹陷），以及受到罕见的山洪暴发影响的地区，一旦再次变得干燥，就会带来新的沉积物供应。
Dust storms are most common in the world’s arid regions and deserts, but can form anywhere where strong winds combine with sediment that can be easily uplifted into the air. Dust is normally generated by a process called ‘saltation’: winds above a threshold wind-speed (typically around 6 to 11 m/s) entrain larger particles (0.1 to 1 mm) which bounce across the surface. These particles are themselves too heavy to be lifted high into the air, but energy released when they impact the soil can overcome binding forces, allowing smaller particles (typically 0.1 to 50 microns) to be emitted and entrained into the atmosphere. Dust aerosol is typically an external mixture of quartz, clays (such as kaolinite, illite), calcite, gypsum and iron oxides. Particles are typically non-spherical and platelet shaped. Ideal conditions for dust uplift are strong winds, little or no vegetation and a dry, sediment-based surface. Emission rates are usually considered to be a cubic function of friction velocity, with no emission below a threshold corresponding to a 10-m wind-speed of around 6 to 11 m/s. Emission is therefore a highly non-linear response that depends only on the relatively rare high wind-speed events, making it a challenge to model. Major dust sources include dried up lake beds (eg the Bodélé Depression in the southern Sahara), and areas affected by rare flash floods which bring new supplies of sediment to be uplifted, as soon as it becomes dry again.
DOI：
10.1007/978-94-017-8978-3
发表时间：
2014-04
期刊：
Mineral Dust
影响因子：
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作者：
P. Knippertz;J. Stuut
通讯作者：
P. Knippertz;J. Stuut