@article{fdi:010053019,
  title = {{V}ariability of aerosol vertical distribution in the {S}ahel},
  author = {{C}avalieri, {O}. and {C}airo, {F}. and {F}ierli, {F}. and {D}i {D}onfrancesco, {G}. and {S}nels, {M}. and {V}iterbini, {M}. and {C}ardillo, {F}. and {C}hatenet, {B}. and {F}ormenti, {P}. and {M}articorena, {B}. and {R}ajot, {J}ean-{L}ouis},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n this work, we have studied the seasonal and inter-annual variability of the aerosol vertical distribution over {S}ahelian {A}frica for the years 2006, 2007 and 2008, characterizing the different kind of aerosols present in the atmosphere in terms of their optical properties observed by ground-based and satellite instruments, and their sources searched for by using trajectory analysis. {T}his study combines data acquired by three ground-based micro lidar systems located in {B}anizoumbou ({N}iger), {C}inzana ({M}ali) and {M}'{B}our ({S}enegal) in the framework of the {A}frican {M}onsoon {M}ultidisciplinary {A}nalysis ({AMMA}), by the {AERO}sol {RO}botic {NET}work ({AERONET}) sun-photometers and by the space-based {C}loud-{A}erosol {L}idar with {O}rthogonal {P}olarization ({CALIOP}) onboard the {CALIPSO} satellite ({C}loud-{A}erosol {L}idar and {I}nfrared {P}athfinder {O}bservations). {D}uring winter, the lower levels air masses arriving in the {S}ahelian region come mainly from {N}orth, {N}orth-{W}est and from the {A}tlantic area, while in the upper troposphere air flow generally originates from {W}est {A}frica, crossing a region characterized by the presence of large biomass burning sources. {T}he sites of {C}inzana, {B}anizoumbou and {M}'{B}our, along a transect of aerosol transport from {E}ast to {W}est, are in fact under the influence of tropical biomass burning aerosol emission during the dry season, as revealed by the seasonal pattern of the aerosol optical properties, and by back-trajectory studies. {A}erosol produced by biomass burning are observed mainly during the dry season and are confined in the upper layers of the atmosphere. {T}his is particularly evident for 2006, which was characterized by a large presence of biomass burning aerosols in all the three sites. {B}iomass burning aerosol is also observed during spring when air masses originating from {N}orth and {E}ast {A}frica pass over sparse biomass burning sources, and during summer when biomass burning aerosol is transported from the southern part of the continent by the monsoon flow. {D}uring summer months, the entire {S}ahelian region is under the influence of {S}aharan dust aerosols: the air masses in low levels arrive from {W}est {A}frica crossing the {S}ahara desert or from the {S}outhern {H}emisphere crossing the {G}uinea {G}ulf while in the upper layers air masses still originate from {N}orth, {N}orth-{E}ast. {T}he maximum of the desert dust activity is observed in this period which is characterized by large {AOD} (above 0.2) and backscattering values. {I}t also corresponds to a maximum in the extension of the aerosol vertical distribution (up to 6 km of altitude). {I}n correspondence, a progressive cleaning up of the lowermost layers of the atmosphere is occurring, especially evident in the {B}anizoumbou and {C}inzana sites. {S}ummer is in fact characterized by extensive and fast convective phenomena. {L}idar profiles show at times large dust events loading the atmosphere with aerosol from the ground up to 6 km of altitude. {T}hese events are characterized by large total attenuated backscattering values, and alternate with very clear profiles, sometimes separated by only a few hours, indicative of fast removal processes occurring, likely due to intense convective and rain activity. {T}he inter-annual variability in the three year monitoring period is not very significant. {A}n analysis of the aerosol transport pathways, aiming at detecting the main source regions, revealed that air originated from the {S}aharan desert is present all year long and it is observed in the lower levels of the atmosphere at the beginning and at the end of the year. {I}n the central part of the year it extends upward and the lower levels are less affected by air masses from {S}aharan desert when the monsoon flow carries air from the {G}uinea {G}ulf and the {S}outhern {H}emisphere inland.},
  keywords = {},
  booktitle = {},
  journal = {{A}tmospheric {C}hemistry and {P}hysics},
  volume = {10},
  numero = {24},
  pages = {12005--12023},
  ISSN = {1680-7316},
  year = {2010},
  DOI = {10.5194/acp-10-12005-2010},
  URL = {https://www.documentation.ird.fr/hor/fdi:010053019},
}