The frequency and source areas of dust storms

Dust events are important geomorphological phenomena in many of the world’s dry lands and four main types can be defined: dust storms, dust haze, blowing dust and dust devils. This paper is concerned with the first two of these categories. Methods for their investigation include the examination of terrestrially observed meteorological data, remote sensing, and deep-sea core sediments. Meteorological data are widely available, but care needs to be exercised in their use. Three main types of remote sensing platforms have proved to be useful: geostationary meteorological satellites, polar orbiting satellites, and the space shuttle orbiters. The deep-sea record provides a long sequence of deposition and helps in the identification of major sinks. Combining the data from these three sources, the major locations of dust storm activity can be identified. However, dust storm frequencies are prone to variation from year to year, and land-use and climatic changes can substantially affect their occurrence. Among important controls of the distributional pattern are the meteorological conditions that entrain dust, including low pressure fronts with intense baroclinal gradients, the convergence zone between cold air masses in regions of monsoonal airflow, katabatic winds, and local convectional cells (haboobs). Another major control is the nature of the surface upon which deflational activity works.