Dust Observations and Climatology - Mineral Dust: A Key Player in the Earth System - page 150

et al. 2013 ; SAMUM; Ansmann et al. 2011 ) used in situ dust measurements in
synergy with satellite observations. Likewise, remote sensing data are essential for
constraining, evaluating and improving aerosol and dust simulations with global and
regional models (Mangold et al. 2011 ;Yuetal. 2013 ; Chap. 9 ) and for progressing
towards operational predictions (Chap. 10 ) . The global (or regional) repetitive view
provided by satellite measurements is valuable to investigate the high spatial and
temporal variability of mineral dust, allowing to progress in the understanding of
transport pathways and identification of main source regions. Current algorithms
allow deriving more detailed information, such as size parameters (Tanré et al. 2011 )
and optical properties (Chap. 12 ) . A better knowledge of all these parameters is
highly needed to reduce current uncertainties with respect to the radiative effects of
mineral dust, both direct and indirect through interactions with clouds (Chap. 11 ) .
In this chapter, we first present a brief review of measurement systems that have
been applied for dust monitoring (Sect. 7.2 ). The main scientific applications of
dust observations, focusing on satellite remote sensing techniques, are presented
in Sect. 7.3 . Section 7.3.1 shows their use for studies of dust source regions and
Sect. 7.3.2 for dust transport monitoring. Long-term satellite dust records that
have been used to explore interannual variability and trends will be presented in
Sect. 7.3.3 , while Sect. 7.3.4 discusses recent progress on observing the vertical
distribution of dust. Conclusion will be given in Sect. 7.4 .

7.2 Observational Systems

The first available dust observations were from synoptic meteorological stations
(Goudie and Middleton 1992 ; Mahowald et al. 2007 ), based on either visibility
reduction or dust weather code analysis (Klose et al. 2010 ;Table 7.2 ). Dust weather
conditions are subjectively determined by trained observers but have the advantage
to be available for decades at many stations located in the arid and semi-arid areas
of Africa and Asia (Cowie et al. 2013 ; Kurosaki and Mikami 2003 ).
More recent dust measurements can generally be divided into two broad cate-
gories: in situ and remote sensing. Remote sensing systems include ground-based
and space-based instruments. Both of these may be performed with either passive
or active techniques. Examples of these different types of observations for dust
monitoring are given in Table 7.2 . Rodriguez et al. ( 2012 ) present a recent review
of long-term in situ measurements of dust. These authors report that only four sites
have been active during at least the last two decades for continuous in situ dust
monitoring, three being in the North Atlantic (Barbados, Miami, Izaña) and one in
the South Pacific (Samoa).
In situ measurements to determine surface dust concentrations generally consist
of collecting particles on filters followed by weighting or chemical analysis in the
laboratory. Table 7.2 lists some examples of in situ dust data that have been available
for more than 1 year, focusing on dust load monitoring, that is, mass concentrations,
derived from various sampling systems (TEOM, filters). Besides surface air quality