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DOI	10.1175/JCLI-D-19-0176.1
	On the structure of the regional-scale circulation over Central Africa: Seasonal evolution; variability; and mechanisms
	Longandjo G.-N.T.; Rouault M.
发表日期	2020
ISSN	0894-8755
起始页码	145
结束页码	162
卷号	33 期号:1
英文摘要	Atmospheric circulation over central Africa is dominated by the tropical easterly jet, the African easterly jet, and the low-level westerly jet. In the lower troposphere, a zonal overturning cell occurs over central Africa, but the mechanisms driving its formation, seasonal evolution, and variability are still unclear. Here, using reanalyses (ERA-Interim, NCEP-2, and JRA-55) and the ECHAM5.3 atmospheric model forced by observed sea surface temperature, we highlight the existence, in the lower troposphere, of a separated single, closed, counterclockwise, and shallow zonal overturning cell, namely, the Congo basin cell. This Congo basin cell persists year round, with maximum intensity and width in August/September and minimum intensity and width in May. This shallow cell extracts heat from the warm central Africa landmass through latent and internal energies and transports it to the cold eastern equatorial Atlantic Ocean, reminiscent of the mixed Carnot-steam cycle. Indeed, the monsoon-like circulation triggered by the zonal surface pressure gradient between the warm central Africa landmass and surrounding cold oceans produces mass convergence at the Congo Air Boundary, providing necessary upward motion to air parcels to destabilize the atmosphere over central Africa. As result, convective updrafts depend on underlying moist static energy and the induced lowlevel westerly jet, controlled by the near-surface land-ocean thermal contrast through the zonal surface pressure gradient between the warm central African landmass and cold eastern equatorial Atlantic Ocean, rather than the midlevel easterly jet. This midlevel easterly jet is formed by the mechanical work that balances the convection associated with the saturation and rainfall. Furthermore, the efficiency of the Congo basin cell determines seasonality over central Africa. © 2019 American Meteorological Society.
英文关键词	Cytology; Pressure gradient; Steam engineering; Surface waters; Troposphere; African easterly jet; Atmospheric circulation; Eastern equatorial Atlantic; Lower troposphere; Maximum intensities; Moist static energy; Sea surface temperature (SST); Tropical Easterly Jet; Oceanography; atmospheric circulation; atmospheric modeling; atmospheric structure; easterly wave; jet stream; monsoon; pressure gradient; seasonal variation; tropical environment; troposphere; updraft; Atlantic Ocean; Atlantic Ocean (Equatorial); Central Africa; Congo Basin
语种	英语
来源期刊	Journal of Climate
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/171544
作者单位	Department of Oceanography, Nansen-Tutu Centre for Environmental Marine Research, University of Cape Town, Cape Town, South Africa; Faculty of Environmental Science and Engineering, Université Nouveaux Horizons, Lubumbashi, Democratic Republic Congo
推荐引用方式 GB/T 7714	Longandjo G.-N.T.,Rouault M.. On the structure of the regional-scale circulation over Central Africa: Seasonal evolution; variability; and mechanisms[J],2020,33(1).
APA	Longandjo G.-N.T.,&Rouault M..(2020).On the structure of the regional-scale circulation over Central Africa: Seasonal evolution; variability; and mechanisms.Journal of Climate,33(1).
MLA	Longandjo G.-N.T.,et al."On the structure of the regional-scale circulation over Central Africa: Seasonal evolution; variability; and mechanisms".Journal of Climate 33.1(2020).