African dry air outbreaks

Chidong Zhang, Jeremy Pennington

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Dry air outbreaks from Africa into the tropical Atlantic region are documented using daily layered precipitable water (LPW) data of satellite remote sensing for 1993-1997. A dry air outbreak is defined as an abrupt decrease in middle-troposphere (700-500 hPa) LPW that is greater than 1 mm d-1 and remains below normal for at least two consecutive days in a reference box off the west coast of Africa. Pathways of individual dry air outbreaks thus identified are tracked both forward and backward in time. Dry air outbreaks intruding into the tropical Atlantic may originate from different source regions: the northern Atlantic Ocean, northern Africa, Sahel, and equatorial Africa. Some of these outbreaks can keep their identities up to 2 weeks, propagate across the Atlantic Ocean, and reach South America and the Caribbean Sea. Boreal summer is the overall peak season, with the majority of the outbreaks occurring north of the Intertropical Convergence Zone (ITCZ). In spring more outbreaks occur south of the ITCZ. Precipitation in the ITCZ tends to decrease during periods of the outbreaks in both spring and summer. Observed large-scale patterns of African dry air outbreaks are compared to known characteristics of African dust outbreaks. The results from this study suggest that African dry air outbreaks should and can be treated as prominent phenomena independent of African dust outbreaks. This study calls for systematic investigations on the similarities and differences between African dust and dry air outbreaks for a better understanding of their effects on weather and climate in the tropical Atlantic region.

Original languageEnglish (US)
JournalJournal of Geophysical Research C: Oceans
Volume109
Issue number20
DOIs
StatePublished - Oct 27 2004

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air
Air
intertropical convergence zone
Dust
Atlantic Ocean
precipitable water
dust
summer
Troposphere
Water
ocean
troposphere
coasts
weather
water
climate
Coastal zones
boxes
remote sensing
Remote sensing

Keywords

  • ITCZ
  • Precipitation
  • Tropical atlantic

ASJC Scopus subject areas

  • Oceanography
  • Astronomy and Astrophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Geophysics
  • Geochemistry and Petrology

Cite this

African dry air outbreaks. / Zhang, Chidong; Pennington, Jeremy.

In: Journal of Geophysical Research C: Oceans, Vol. 109, No. 20, 27.10.2004.

Research output: Contribution to journalArticle

Zhang, Chidong ; Pennington, Jeremy. / African dry air outbreaks. In: Journal of Geophysical Research C: Oceans. 2004 ; Vol. 109, No. 20.
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