Dust Observations and Climatology - Mineral Dust: A Key Player in the Earth System - page 159

passes per month), have been shown to provide reliable AOD over bright desert
surfaces (Martonchik et al. 2004 ) and can complement past and current satellite
analysis. Other approaches like inverse modelling, which combines models and
multiple satellite datasets, are promising to retrieve mineral dust sources (Dubovik
et al. 2008 ;Wangetal. 2012 ; Chap. 10 ) .

7.3.2 Transport

General Features

From a general point of view, the development of satellite technology has played a
key role in improving our knowledge of transported dust. One of the first highlights
is that desert dust is the species responsible for the largest and most persistent
aerosol loads over the world's oceans as indicated by all global aerosol satellite
maps (Husar et al. 1997 ;Hermanetal. 1997 ). The first direct application of satellite
observations has been to track long-range transport of desert dust. Satellites can
provide spectacular imagery of major dust events, showing large plumes crossing
the entire ocean basins, especially over the North Atlantic and Pacific (Husar
et al. 2001 ; Hsu et al. 2006 ;Yuetal. 2013 ). One of the first studies of this kind
has monitored the daily evolution of AOD during a dust event over the North
Atlantic in March 1988 based on Meteosat observations (Jankowiak and Tanré
1992 ). Interestingly, some studies also attempted to go beyond simple detection
with imagery to estimate columnar mass transport of desert dust (Dulac et al. 1992 ;
Kaufman et al. 2005 ) or to derive more detailed characterization of transported dust
(Kalashnikova and Kahn 2008 ). Generally the trans-Atlantic transport of dust has
been well documented with satellite observations, while the trans-Pacific transport
has been studied less. Other transport paths of dust would require more research
efforts, particularly in the Southern Hemisphere where only a few observational
studies are available (e.g. from the Patagonia desert; Gasso and Stein 2007 ;Lietal.
2010 ). Despite the dominance of dust mass emitted and transported from tropical
and mid-latitude arid regions, dust events also occur in less explored areas at high
latitudes such as Alaska, New Zealand or Iceland (Prospero et al. 2012 ), where the
analysis of satellite imagery is of primary interest.
One main feature of dust transport revealed by ground- and space-based obser-
vations is high variability in space and time. Temporal variability is evident at
timescales from the diurnal cycle to multiannual changes, including large seasonal
variations. The main drivers are meteorological factors (see Chap. 6 ) thatexert
control on both emission and transport processes. As North Africa is the largest
dust source, its transport over the surrounding marine regions has been investigated
most in the past, with three major pathways identified, that is, (1) westwards and
southwards to the North Atlantic Ocean, (2) towards the Mediterranean and Europe
(Dulac et al. 1992 ; Israelevich et al. 2012 ) and (3) towards the eastern Mediterranean
and the Middle East (Engelstaedter et al. 2006 ). Characteristics and seasonality of