Abstract. The Sahelian belt is known to be a region where atmospheric levels of suspended mineral dust are among the highest observed on Earth. In the framework of the AMMA (African Monsoon Multidisciplinary Analysis) International Program, a transect of 3 ground based stations, the "Sahelian Dust Transect" (SDT), has been deployed in order to obtain quantitative information on the mineral dust content and its variability over the Sahel. The three stations, namely Banizoumbou (Niger), Cinzana (Mali) and M'Bour (Senegal) are aligned around 14 • N along the east-westward main pathway of the Saharan and Sahelian dust towards the Atlantic Ocean. We discuss data collected between January 2006 and December 2008 to investigate the main characteristics of the mineral dust concentration over West Africa and their connection with the dominant meteorological situations. The succession of the dry season during which the Sahel is under the influence of the dry Harmattan wind and the wet season induced by the entrance of the monsoon flow is clearly identified from the basic meteorological parameters (air temperature and moisture, wind direction). Atmospheric dust concentrations at the three stations exhibit a similar seasonal cycle, with a monthly maximum during the dry season and a minimum occurring during the rainy season, indicating that the general pattern of dust concentration is similar at regional scale. This seasonal cycle of the dust concentrations Correspondence to: B. Marticorena (marticorena@lisa.univ-paris12.fr) is not phased with the seasonal cycle of surface wind velocity locally measured, suggesting that it is mainly controlled by Saharan dust transport. Local dust emissions induced by strong surface winds are responsible for the occurrence of extremely high daily concentrations observed at the beginning of the rainy season. A decrease in the dust concentration is observed when moving from Niger to Senegal.

West Africa and the adjacent oceanic regions are very important locations for studying dust properties and their influence on weather and climate. The SHADOW (study of SaHAran Dust Over West Africa) campaign is performing a multiscale and multilaboratory study of aerosol properties and dynamics using a set of in situ and remote sensing instruments at an observation site located at the IRD (Institute for Research and Development) in Mbour, Senegal (14 • N, 17 • W). In this paper, we present the results of lidar measurements performed during the first phase of SHADOW (study of SaHAran Dust Over West Africa) which occurred in March-April 2015. The multiwavelength Mie-Raman li-dar acquired 3β + 2α + 1δ measurements during this period. This set of measurements has permitted particle-intensive properties, such as extinction and backscattering Ångström exponents (BAE) for 355/532 nm wavelengths' corresponding lidar ratios and depolarization ratio at 532 nm, to be determined. The mean values of dust lidar ratios during the observation period were about 53 sr at both 532 and 355 nm, which agrees with the values observed during the SAMUM-1 and SAMUM-2 campaigns held in Morocco and Cabo Verde in 2006 and 2008. The mean value of the particle depolariza-tion ratio at 532 nm was 30 ± 4.5 %; however, during strong dust episodes this ratio increased to 35 ± 5 %, which is also in agreement with the results of the SAMUM campaigns. The backscattering Ångström exponent during the dust episodes decreased to ∼ −0.7, while the extinction Ångström exponent , though negative, was greater than −0.2. Low values of BAE can likely be explained by an increase in the imaginary part of the dust refractive index at 355 nm compared to 532 nm. The dust extinction and backscattering coefficients at multiple wavelengths were inverted to the particle mi-crophysics using the regularization algorithm and the model of randomly oriented spheroids. The analysis performed has demonstrated that the spectral dependence of the imaginary part of the dust refractive index may significantly influence the inversion results and should be taken into account.

Available data on the long-term consequences of preschool stunting are scarce and conflicting. The objective of this study was to assess the amount of catch-up growth from preschool stunting and the effect of migration (change in environment) during adolescence. A cohort study from preschool age (1-5 y) to adulthood (18-23 y) was conducted among 2874 subjects born in a rural area of Senegal. The subjects were divided into 3 groups of preschool stunting: none, mild, and marked, with height-for-age Z-scores of >-1, -2 to -1, and <-2, respectively. At follow-up, the history of migration was recalled. Mean height was 161.3 cm for girls and 174.0 cm for boys (>/=20 y). Stunted subjects remained smaller than the others: the age-adjusted height deficit between the 2 extreme categories was 6.6 and 9.0 cm in girls and boys, respectively. However, their height increment from early childhood to adulthood differed (69.3, 70.5, and 72.0 cm, P = 0.0001, and 78.9, 80.0, and 80.3 cm, P < 0.01, for nonstunted, mildly stunted, and markedly stunted girls and boys, respectively). The duration of labor migration to the city was associated with height increment in girls only in a nonlinear relation (adjusted means: 67.2, 69.3, 67.4, and 67.7 cm for 4 groups of increasing duration, P < 0.01). In conclusion, Senegalese children caught up in height prior to adulthood, with the adult means approximately 2 cm below the WHO/NCHS reference. However, this global catch up did not reduce height differences between formerly stunted and nonstunted children to any greater extent and it was not enhanced by labor migration.

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Mineral dust deposits were collected at Mbour, Senegal, throughout the spring of 2006 and especially during the well‐documented March 7–13 large Saharan dust outbreak. During this 7‐day period, significant changes in mass flux, grain‐size, clay mineralogy and Sr and Nd isotopic compositions were recorded, indicating distinct provenances for the dust transported and deposited during and outside the event. All these terrigenous proxies, as well as freshwater diatom taxa, also showed significant temporal variations during the outbreak, implying contributions from at least two different provenance regions. Tri‐dimensional back‐trajectories and satellite imaging enabled us to link those distinct signatures to regions increasingly to the southeast within a large area covering Mauritania, Mali and southern Algeria, identified by the Total Ozone Mapping Spectrometer (TOMS) as the main source of the prominent winter/spring plume over the tropical Atlantic. The multiproxy characterization of the March 7–13 dust fall therefore enables us to typify the terrigenous signature of two different regions supplying dust off West Africa, and provide valuable clues for the interpretation of Northeastern Tropical Atlantic Ocean dust sedimentary records in terms of changes in provenance regions and transport systems. Additionally, because dust deposition data are scarce, flux and grain size data obtained in this study, among other parameters such as clay assemblages, provide important constraints for atmospheric transport models and dust deposition budget estimates in this area.