Research

摘要

Dust storms which typically originate in the world's desert and semi-desert drylands can have wide-ranging impacts. The geographer, writer and broadcaster Nick Middleton has recently reviewed the global hazards of desert dusts (Middleton, 2017, Aeolian Research, v.24, pp.53-63). Strong turbulent winds blowing over the surface can pick up silt and clay sized particles, reducing visibility to less than 1 km (Fig. 14). In severe events, the concentration of particulate matter, with a particle size of less than 10 μm (PM10) can exceed 15000 μg/m3. Meteorological data and satellite-borne sensors provide a picture of the present day dusts sources, with the Sahara being the most important (contributing 50 percent of the total global dust), followed by China, Central Asia, Arabia and Australia. Within these dryland areas, large basins with internal drainage, alluvial deposits, playas and piedmont alluvial fans are typically richer in dust-sized sediment grains and consequently supply most of the desert dust. Although estimates range hugely, the total mineral dust load added to the atmosphere each year is enormous, with values ranging between 1 and 3 billion tonnes per annum.