English "Simoom", small and extremely hot and dry local wind in
Arabia
and the Sahara. Its temperature often reaches 55° C (about 130°
F), and its humidity sometimes falls under 10 percent. Intensive ground
heating under a cloudless sky causes the Simoom. The Arabic word means
“poison wind” and refers to the wind's tendency to cause heatstroke.
Introduction
A large portion of airborne particulate matter is derived from arid and
barren regions of the
Earth and is distributed all over the globe. The most prominent example
of this transport is
the export of desert aerosols from the Saharan area (cf. figures),
which extend
over areas of several 100.000 km2. This dust may be regarded
as being
distributed over the
Northern Hemisphere. Since transport distances up to 10.000 km are
observed, desert dust is
virtually omnipresent within the atmosphere.
By its omnipresence, the desert aerosol, consisting of a mixture of
mineral matter from soil erosion and significant contributions of
sulfur, nitrogen compounds, soot from combustion sources, and
particulate matter from the biosphere, is causing a significant impact
on the atmospheric radiation field. Dust not only scatters but also
absorbs solar radiation, and also absorbs and emits outgoing longwave
radiation. The magnitude and even the sign of the direct radiative dust
forcing is uncertain. It depends on the optical properties of dust, its
vertical distribution, cloud cover, and the albedo of the underlying
surface. Strong columnar aerosol mass loadings, which are frequently
observed over deserts and during long-range transport of dust
outbreaks, cause warming of layers aloft and thus changes of the
atmospheric (in)stability. To date no weather model includes any
feedback between these strong diabatic heating rates and atmospheric
dynamics. A magnitude of direct mineral dust forcing of about –0.5 Wm-2
to 0.5 Wm-2 is actually discussed and thus indicates global
significance in comparing with greenhouse gases and other effects.
Dust influences the Earth’s system in several ways. The presence of
dust may alter cloud optical properties by changing the number of cloud
condensation or ice nuclei. The efficiency of dust particles to form
cloud drop nuclei may alter during transport due to mixing with soluble
aerosol species. This can influence both the brightness of clouds and
the formation of rain. Dust particles can change chemical reactions in
the atmosphere because of their large surface area. Micronutrients
(e.g., Fe) deposited with dust particles impact on the marine and
terrestrial ecosystems, thus influencing the carbon cycle and
potentially changing atmospheric greenhouse gases. The impacts of these
indirect dust effects are very uncertain.
Dust outbreaks above Europe, like the one on October 11-16, 2001, were
also thouroughly surveyed by EARLINET.
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Dust outbreak on October 13,
2001, also observed by EARLINET
|
Recording EARLINET stations (red) |
Expectations
|
A plume of Saharan desert dust (light brown
pattern)
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|
Partners
| Research Group | Partners | Title of Project |
|---|---|---|
| Institute for Physics of the Atmosphere, German Aerospace Center (DLR) | Petzold, Ehret, Schumann | Airborne in situ and remote sensing studies on the vertical and area distribution of microphysical and optical properties of Saharan dust |
| Institute for Remote Sensing, Deutsches German Aerospace
Center (DLR), Leibniz Institute for Tropospheric Research, Leipzig (IfT) |
Trautmann, Wendisch, Heintzenberg | Radiative properties of Sahara dust, in-situ aircraft measurements and model calculations |
| Max Planck Institute for Biogeochemistry Jena, Leibniz Institute for Tropospheric Research, Leipzig (IfT) |
Tegen, Heintzenberg, Renner | Regional modeling of the Saharan dust cycle |
| Leibniz Institute for Tropospheric Research, Leipzig (IfT), Institute for Meteorology of the University of Munich |
Ansmann, Wiegner | Vertically resolved characterization of Saharan dust based on observations with lidars |
| Leibniz Institute for Tropospheric Research, Leipzig (IfT) | Heintzenberg, Wiedensohler | Hygroscopicity and optical properties of dust particles: Technical development and field application |
| Institute for Physics of the Atmosphere, University of Mainz, Institute for Mineralogy, Technical University of Darmstadt |
Jaenicke, Schütz, Weinbruch | Physicochemical parameters of desert aerosols |
| Institute for Environmental Physics and Remote Sensing, University of Bremen | Burrows, v. Hoyningen-Huene |
Dust aerosol REtrievAl from space-borne instruMentS (DREAMS) |
| Laboratoire de Physique de l`Atmosphère, Departement de Physique, Faculté des Sciences, Oujda, Morocco | Mohammed Diouri | Columnar optical aerosol properties over Morocco |
Instrument
Our group will participate with the six-wavelength
lidar, a Sun
photometer, and a radiosonde station.
Dust-related publications of our group:
Mattis, I., Ansmann, A., Müller, D., Wandinger, U. and
Althausen, D.
2002. Dual-wavelength Raman lidar observations of the
extinction-to-backscatter ratio of Saharan dust. Geophys. Res. Lett.,
29, 2002GL014721.
Ansmann, A., Bösenberg, J., Chaikovsky, A. P., Comerón,
A., Eixmann,
R., Freudenthaler, V., Ginoux, P., Konguem, L., Linné, H.,
Márquez, M.
Á. L., Manoj, S., Matthias, V., Mattis, I., Mitev, V.,
Müller, D.,
Nickovic, S., Pelon, J., Sauvage, L., Sobolewsky, P., Stohl, A.,
Torres, O., Vaughan, G., Wandinger, U. and Wiegner, M. 2003. Long-range
transport of Saharan dust to northern Europe: The 11-16 October 2001
outbreak with EARLINET. J. Geophys. Res.,
108, 2003JD003757.
Müller, D., Mattis, I., Wandinger, U., Ansmann, A., Althausen, D., Dubovik, O., Eckhardt, S. and Stohl, A. 2003. Saharan dust over a Central European EARLINET-AERONET site: Combined observations with Raman lidar and Sun photometer. J. Geophys. Res., 108, 2002JD002918.
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