@article{fdi:010080467,
  title = {{D}aytime low-level clouds in {W}est {A}frica : occurrence, associated drivers, and shortwave radiation attenuation},
  author = {{D}anso, {D}. {K}. and {A}nquetin, {S}. and {D}iedhiou, {A}rona and {K}ouadio, {K}. and {K}obea, {A}. {T}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}his study focuses on daytime low-level clouds ({LLC}s) that occur within the first 2 km of the atmosphere over {W}est {A}frica ({WA}). {T}hese daytime {LLC}s play a major role in the earth's radiative balance, yet their understanding is still relatively low in {WA}. {W}e use the state-of-the-art {ERA}5 dataset to understand their occurrence and associated drivers as well as their impact on the incoming surface solar radiation in the two contrasting {G}uinean and {S}ahelian regions of {WA}. {T}he diurnal cycle of the daytime occurrence of three {LLC} classes namely {N}o {LCC}, {LLC} {C}lass-1 ({LLC}s with lower fraction), and {LLC} {C}lass-2 ({LLC}s with higher fraction) is first studied. {T}he monthly evolutions of hourly and long-lasting {LLC} (for at least 6 consecutive hours) events are then analyzed as well as the synoptic-scale moisture flux associated with the long-lasting {LLC} events. {F}inally, the impact of {LLC} on the surface heat fluxes and the incoming solar irradiance is investigated. {D}uring the summer months in the {G}uinean region, {LLC} {C}lass-1 occurrence is low, while {LLC} {C}lass-2 is frequent (occurrence frequency around 75 % in {A}ugust). {I}n the {S}ahel, {LLC} {C}lass-1 is dominant in the summer months (occurrence frequency more than 80 % from {J}une to {O}ctober); however the peak occurrence frequency of {C}lass-2 is also in the summer. {I}n both regions, events with {N}o {LLC} do not present any specific correlation with the time of the day. {H}owever, a diurnal evolution that appears to be strongly different from one region to the other is noted for the occurrence of {LLC} {C}lass-2. {LLC} occurrence in both regions is associated with high moisture flux driven by strong southwesterly winds from the {G}ulf of {G}uinea and significant background moisture levels. {LLC} {C}lass-2 in particular leads to a significant reduction in the upward transfer of energy and a net downward energy transfer caused by the release of large amounts of energy in the atmosphere during the cloud formation. {I}n {J}uly, {A}ugust, and {S}eptember ({JAS}), most of the {LLC} {C}lass-2 events may likely be the low-level stratiform clouds that occur frequently over the {G}uinean region, while they may be deep convective clouds in the {S}ahel. {A}dditionally, {LLC} {C}lass-2 causes high attenuation of the incoming solar radiation, especially during {JAS}, where about 49 % and 44 % of the downwelling surface shortwave radiation is lost on average in {G}uinea and the {S}ahel, respectively.},
  keywords = {{AFRIQUE} {DE} {L}'{OUEST} ; {ZONE} {SAHELIENNE} ; {ZONE} {GUINEENNE}},
  booktitle = {},
  journal = {{E}arth {S}ystem {D}ynamics},
  volume = {11},
  numero = {4},
  pages = {1133--1152},
  ISSN = {2190-4979},
  year = {2020},
  DOI = {10.5194/esd-11-1133-2020},
  URL = {https://www.documentation.ird.fr/hor/fdi:010080467},
}