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Meridional ozone gradients in the African upper troposphere
Author(s) -
Sauvage B.,
Thouret V.,
Cammas J.P.,
Brioude J.,
Nédélec P.,
Mari C.
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl028542
Subject(s) - intertropical convergence zone , hadley cell , troposphere , ozone , atmospheric sciences , zonal and meridional , climatology , environmental science , tropospheric ozone , relative humidity , equator , latitude , geology , meteorology , climate change , general circulation model , geography , precipitation , oceanography , geodesy
This study presents regular observations from the MOZAIC data base over Africa (1994–2004) to highlight the role of Hadley cells in tropical ozone production. We show the presence in the African upper troposphere (9–12 km) of a minimum of ozone and of a maximum of relative humidity that both follow the meridional migration of the Inter‐Tropical Convergence Zone (ITCZ). We suggest that mechanisms contributing to meridional ozone gradients (0.3 to 1.5 ppbv deg −1 ) on both sides of the ozone minimum in the 20°S–20°N latitude band are (1) the vertical transport of relatively poor ozone air masses by tropical convection, and (2) the photochemical production of ozone in upper‐level branches of the Hadley circulation. Depending on the season and on the meridional side of the ITCZ, ozone precursors injected in the ascending branch of the ITCZ include biomass burning, biogenic, lightning and anthropogenic emissions.