@article{fdi:010042589,
  title = {{T}he west {A}frican monsoon dynamics. {P}art {III} : the quasi-biweekly zonal dipole},
  author = {{M}ounier, {F}. and {J}anicot, {S}erge and {K}iladis, {G}. {N}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}his paper presents an investigation of the mechanisms giving rise to the main intraseasonal mode of convection in the {A}frican monsoon during northern summer, here identified as the quasi-biweekly zonal dipole ({QBZD}). {T}he {QBZD} is primarily characterized by a quasi-stationary zonal dipole of convection whose dimension is larger than the {W}est {A}frican monsoon domain, with its two poles centered along the {G}uinean coast and between 30 and 60 {W} in the equatorial {A}tlantic. {T}he {QBZD} dynamical processes within the {A}tlantic-{A}frica domain are examined in some detail. {T}he {QBZD} has a dipole pattern associated with a {W}alker-type circulation in the near-equatorial zonal plane. {I}t is controlled both by equatorial atmospheric dynamics through a {K}elvin wave-like disturbance propagating eastward between its two poles and by land surface processes over {A}frica, inducing combined fluctuations in surface temperatures, surface pressure, and low-level zonal winds off the coast of {W}est {A}frica. {W}hen convection is at a minimum over central and {W}est {A}frica, a lack of cloud cover results in higher net shortwave flux at the surface, which increases surface temperatures and lowers surface pressures. {T}his creates an east - west pressure gradient at the latitude of both the {ITCZ} (10 degrees {N}) and the {S}aharan heat low (20 degrees {N}), leading to an increase in eastward moisture advection inland. {T}he arrival from the {A}tlantic of the positive pressure signal associated with a {K}elvin wave pattern amplifies the low-level westerly wind component and the moisture advection inland, leading to an increase in convective activity over central and {W}est {A}frica. {T}hen the opposite phase of the dipole develops. {P}ropagation of the {QBZD} convective envelope and of the associated 200 high-level velocity potential anomalies is detected from the eastern {P}acific to the {I}ndian {O}cean. {W}hen the effect of the {K}elvin wave propagation is removed by filtering, the stationary character of the {QBZD} is highlighted. {T}he impact of the {QBZD} in combination with a {K}elvin wave is illustrated by a case study of the monsoon onset in 1984.},
  keywords = {},
  booktitle = {},
  journal = {{J}ournal of {C}limate},
  volume = {21},
  numero = {9},
  pages = {1911--1928},
  ISSN = {0894-8755},
  year = {2008},
  DOI = {10.1175/2007{JCLI}1706.1},
  URL = {https://www.documentation.ird.fr/hor/fdi:010042589},
}