Meteorological Aspects of Dust Storms - Mineral Dust: A Key Player in the Earth System - page 120

Chapter 6
Meteorological Aspects of Dust Storms
Peter Knippertz
Abstract Dust emission requires the combination of deflatable soil material and
near-surface wind speeds above the local emission threshold. Across the many
dust source regions on Earth a number of generic meteorological phenomena can
be identified and classified: (1) Large-scale monsoon-type flows associated with
an acceleration towards a continental heat low, predominantly in late spring and
early summer; (2) mobile synoptic-scale systems such as anticyclones, cyclones
and their cold fronts, typically in late winter and spring; (3) gust fronts generated
by outflow from moist convective storms, most common during the beginning
of the summer rainy season; (4) intense dry convection in the daytime planetary
boundary layer particularly during summer, leading to the generation of dust devils
and dusty plumes. These processes can locally be modified by topographic effects
and are usually characterised by marked diurnal cycles, for example caused by
the development and subsequent breakdown of nocturnal low-level jets in areas
of sufficiently large pressure gradients and stable nighttime conditions. In this
chapter the different meteorological phenomena listed above will be explained and
illustrated using ground-based observations, satellite data and measurements from
field campaigns as well as data from meteorological models.
Keywords Meteorology ￿ Large-scale circulations ￿ Cyclones ￿ Anticyclones ￿
Moist convection ￿ Dry convection ￿ Diurnal variations ￿ Topographic effects ￿
Modelling ￿ Cold front ￿ Dust emission ￿ Wind