Comparisons of day-time and night-time dust accumulation in a desert region

The aeolian accumulation of natural atmospheric dust in a desert environment was investigated during a 24-month experiment. Accumulation was measured with marble collectors every month. At the same time, wind speed, dust concentration, dew formation and rainfall were recorded. Atmospheric stability was measured from a 90 m tower several km from the test site. Dust accumulation by day was systematically higher than dust accumulation at night. Also, dust concentration was higher, but the higher concentrations cannot completely explain die higher accumulation values. Both average monthly concentration and accumulation are considerably influenced by the occurrence of high-magnitude dust events, either dust storms or dust hazes. The dust that accumulated at night was systematically coarser than the dust that accumulated during the day. No seasonal trend was observed in the grain size of the sediment. The velocity of accumulation, defined as the ratio between accumulation and concentration, varied between 1·18 m.s^-1 and 4·53 m.s^-1. Dew formation did not seem to have a serious impact upon dust accumulation, whereas wind erosion, and especially the erosion occurring during heavy gusts, appears to play a very important role, since these gusts may be able to blow away large amounts of sediment that accumulated during the preceding hours, days or even weeks.