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Control of atmospheric export of dust from North Africa by the North Atlantic Oscillation

Nature volume 387, pages 691–694 (1997)Cite this article

Abstract

All year long, massive airborne plumes of desert dust from the Sahara and surrounding regions are exported to the North Atlantic Ocean1 and the Mediterranean Sea2. The mass of African dust transported in the atmosphere is large—about one billion tonnes per year (ref. 3)—and it has been suggested that the wind-blown dusts have a substantial influence on the regional radiative budget4,5,6. Here we use daily satellite observations of airborne dusts7 to obtain an 11-year regional-scale analysis of dust transport out of Africa. The substantial seasonal variability over the Atlantic Ocean and Mediterranean Sea can be explained by the synoptic meteorology. Interannual variations in dust transport are similar over both regions, and are well correlated with the climatic variability defined by the North Atlantic Oscillation8. This large-scale climatic control on the dust export is effected through changes in precipitation and atmospheric circulation over the regions of dust mobilization and transport. Such natural variability is so large that it is difficult to resolve any anthropogenic influences on atmospheric dust loads, such as those due to desertification or land-use changes. It seems likely that the North Atlantic Oscillation will also affect the distribution—and radiative influence—of other aerosols.

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Figure 1: Seasonal maps of the desert dust optical depth (at a wavelength of 0.55 μm) over the Atlantic Ocean and the Mediterranean Sea, obtained by averaging 4,000 daily Meteosat images of the solar (VIS) channel from 1984 to 1994.
Figure 2: Comparison between the North Atlantic Oscillation (NAO) index (bold continuous line; J.W. Hurrell, personal communication) and the mean optical depth of desert dust in summer from 1983 to 1994 over the whole Mediterranean (open circles) and the Atlantic zone defined in Fig. 1 (filled circles).
Figure 3: Maps of the desert dust optical depth (averaged from March to August) over the Mediterranean and the Atlantic for a dust-poor year (1986; left) and a dust-rich year (1989; right).
Figure 4: Comparison of the North Atlantic Oscillation (NAO) index (bold continuous line; J.W. Hurrell, personal communication) between 1964 and 1996 with the annual mean of desert dust surface concentrations at Barbados, West Indies, between 1965 and 1995 (filled circles; J. M. Prospero, personal communication).

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Acknowledgements

We thank J. W. Hurrell and J. M. Prospero for providing us with their data, and for their comments; Y. Balkanski for facilitating the access to the AVISO archive; V. Masson, J. Orr and B. Ziv for discussions about climatic variability; and W. Guelle and X. Schneider for their utility computer codes. This work was supported by the CEA and the CNRS.

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Authors and Affiliations

  1. *Laboratoire de Modlisation du Climat et de l'Environnement, CEA, Gif-sur-Yvette, 91191, cedex, France

    Cyril Moulin

  2. †Centre des Faibles Radioactivités, CNRS-CEA, Gif-sur-Yvette, 91198, cedex, France

    Claude E. Lambert & François Dulac

  3. ‡Environmental and Risk Assessment Section, SNRC, Yavne, 81800, Israel

    Uri Dayan

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  1. Cyril Moulin
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  2. Claude E. Lambert
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  4. Uri Dayan
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Correspondence to François Dulac.

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Moulin, C., Lambert, C., Dulac, F. et al. Control of atmospheric export of dust from North Africa by the North Atlantic Oscillation. Nature 387, 691–694 (1997). https://doi.org/10.1038/42679

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