Introduction - Mineral Dust: A Key Player in the Earth System - page 7

￿ With the first satellite of the Meteosat Second Generation becoming operational

in January 2004, the tracking of individual dust plumes with high resolution
in time and space became possible, both during day and night, at least in a
qualitative sense. This has significantly enhanced our understanding of sources
(e.g. Schepanski et al. 2007 ) as well as dust storm dynamics (e.g. Knippertz and
Todd 2012 ).

￿ The first spaceborne lidar, which allowed the retrieval of a detailed vertical profile

of the dust distribution, is the Cloud-Aerosol Lidar with Orthogonal Polarization
(CALIOP) onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite
Observations (CALIPSO) satellite, which was launched in April 2006. Despite its
low space-time coverage, CALIOP data give unprecedented insight into vertical
mixing and layering processes (Winker et al. 2009 ).

￿ New retrieval development: Traditional satellite retrievals in the visible part of the

spectrum struggle to see dust over bright desert areas due to the small contrast
to the underlying surface and are only available during the day. Recent years
have seen the development of new retrievals for optical thickness that overcome
this problem by (additionally) using channels outside the visible band such
as in the near-ultraviolet (Deep Blue algorithm, Hsu et al. 2004 ) and infrared
(Spinning Enhanced Visible and Infrared Imager (SEVIRI), Brindley and Ignatov
2006 ; Infrared Atmospheric Sounding Interferometer (IASI), Klüser et al. 2011 ;
Atmospheric Infrared Sounder (AIRS), Peyridieu et al. 2010 ).

Recent years have also seen a considerable increase in the number and complex-
ity of dust models used both for research and for forecasting purposes (Chap. 9 ) .
Due to the increase of computer power, these models can be run in higher horizontal
and vertical resolution to allow for investigations of smaller-scale meteorological
processes such as effects of cold outflows from thunderstorms on dust emission
(Reinfried et al. 2009 ; Heinold et al. 2013 ; Chap. 6 ) . At the same time there have
been some new approaches to treat emission processes in models at high resolution
(Kok 2011 ;KloseandShao 2012 ; Chap. 5 ) . An important new development from
an operational perspective is the introduction of dust prediction models at several
modelling centres around the world, which generate daily forecasts of parameters
such as near-surface concentrations and optical thickness for air-quality and weather
warning purposes (Chap. 10 ) . These include both regional and global models. In
contrast to research models, these new systems include the assimilation of satellite
and ground-based observations, making them an important tool for climatological
monitoring as well. The new capabilities in dust observations also play a role in
model evaluation and development. Many of the latest versions of both operational
and research models include couplings between dust and radiation fields (Chaps. 11
and 13 ) , while couplings with cloud microphysics (Chap. 12 ) have become more
widespread in specialised research models.
The increasing complexity in both models and satellite retrievals has led to
the recognition that more detailed information on the characteristics and size
distribution of dust particles (Chap. 2 ) are needed to determine necessary input
parameters and to evaluate the credibility of our approaches. Therefore, a number