Diabatic heating, divergent circulation and moisture transport in the African monsoon system

Samson Hagos, Chidong Zhang

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


The dynamics of the West African monsoon system is studied through the diagnosis of the roles of diabatic heating in the divergent circulation and moisture transport. The divergent circulation is partitioned into latent-heating and non-latent-heating (the sum of surface sensible heat flux and radiative heating) driven components based on its field properties and its relationship with diabatic heating profiles. Roles of latent and non-latent diabatic heating in the moisture transport of the monsoon system are thus distinguished. The gradient in surface sensible heat flux between the Saharan heat-low and the Gulf of Guinea drives a shallow meridional circulation, which transports moisture far into the continent on the northern side of the monsoon rain band and thereby promotes the seasonal northward migration of monsoon precipitation. In contrast, the circulation directly associated with latent heating is deep and the corresponding moisture convergence maximum is within the region of precipitation and thus enhances local monsoon precipitation. Meanwhile, latent heating also induces dry air advection from the north. The seasonal northward migration of precipitation is encouraged by neither of the two effects. On the other hand, the divergent circulation forced by remote latent heating influences local moisture distribution through advection. Specifically by bringing Saharan air from the north, and driving moisture to the adjacent oceans, global latent heating has an overall drying effect over the Sahel.

Original languageEnglish (US)
Pages (from-to)411-425
Number of pages15
JournalQuarterly Journal of the Royal Meteorological Society
Issue numberSUPPL. 1
StatePublished - Jan 2010


  • African monsoon
  • Diabatic heating
  • Divergent circulation
  • Moisture transport

ASJC Scopus subject areas

  • Atmospheric Science


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