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Accueil du site → Doctorat → Royaume-Uni → 1999 → Dust-climate interactions in the Sahel-Sahara zone of northern Africa, with particular reference to late twentieth century Sahelian drought

University of East Anglia (1999)

Dust-climate interactions in the Sahel-Sahara zone of northern Africa, with particular reference to late twentieth century Sahelian drought

Brooks Nick

Titre : Dust-climate interactions in the Sahel-Sahara zone of northern Africa, with particular reference to late twentieth century Sahelian drought.

Auteur : Nick Brooks

Université de soutenance : University of East Anglia

Grade : Doctor of Philosophy (PhD) 1999

Résumé
Since the 1950s, the Sahel region of Africa has experienced a decline in rainfall, while levels of atmospheric dust in the region have increased. The potential of atmospheric dust to modify the radiative structure of the atmosphere, and its absence from GCM simulations, suggests that an investigation of the role of mineral aerosols in regional climate modification in the Sahel is appropriate.The Infra-red Difference Dust Index (IDDI), a new satellite-derived proxy dust-loading climatology for 1984-1993, is used to examine variability of dust production in the Sahel-Sahara region. The relative roles of rainfall and the synoptic climatology in determining dust production are investigated, and the likelihood that widespread land degradation in the Sahel has contributed to increased atmospheric dust concentrations is assessed. The potential of atmospheric dust to exert an influence on the thermal and convective properties of the atmosphere is revealed through correlation analyses of IDDI and NCEP/NCAR climatological reanalysis data.It is inferred that the observed increases in dust concentrations over the Sahel are most probably due to a combination of changes in atmospheric mobilisation and transport mechanisms, and changes in the regional hydrological and geomorphological cycles. There is little evidence that anthropogenic land degradation has resulted in increased dust mobilisation. Atmospheric dust has the largest thermal impact over the Sahel and southern Sahara, where it results in widespread cooling below about 3-4 kilometres, and a more limited warming in the middle troposphere. There is evidence that dust modifies the atmospheric dynamics, possibly inhibiting the onset of the West African monsoon in May of some years.

Mots Clés : abridged - dust, drought and land degradation

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Page publiée le 27 décembre 2011, mise à jour le 6 février 2017