Influence of the Madden–Julian Oscillation on Southern African Summer Rainfall

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dc.contributor.authorPohl, B
dc.contributor.authorRichard, Y
dc.contributor.authorFauchereau, N
dc.date.accessioned2021-10-08T07:04:26Z
dc.date.available2021-10-08T07:04:26Z
dc.date.issued2007
dc.description.abstractComposite maps of outgoing longwave radiation (OLR) anomalies over the Madden-Julian oscillation (MJO) cycle show marked intraseasonal fluctuations over southern Africa (south of 15°S). Large-scale convective clusters are seen to propagate eastward and then northward over the continent, mainly between 10° and 20°S. The corresponding response of the rainfall field presents the alternation, over the cycle, of dry and humid phases, which are both significant. Moisture flux anomalies indicate an intraseasonal modulation of the midtropospheric easterly flow over the Congo basin at 700 hPa; these fluctuations are coupled to meridional flux anomalies that extend from the tropical to the subtropical austral latitudes, and favor occurrences of wet or dry conditions over the domain. Though statistically significant, the influence of the MJO on southern Africa is however not homogeneous spatially, and only the tropical areas exhibit sharp periodicities in the 30-60-day period range. The OLR dipole observed in previous studies at the interannual and synoptic time scales between the hinterland parts of southern Africa and the southwestern Indian Ocean in the north of Madagascar is investigated next, as it also shows strong fluctuations at the intraseasonal time scale. The study points out that the dipole is partly influenced by the MJO, though the strongest periodicities are found for slightly longer periods (35-80 days) than those typically associated with the oscillation. The forcing of the MJO on the OLR dipole, though significant, remains thus partial.
dc.identifier.apacitationPohl, B., Richard, Y., & Fauchereau, N. (2007). Influence of the Madden–Julian Oscillation on Southern African Summer Rainfall. <i>Journal of Climate</i>, 20(16), 4227 - 4242. http://hdl.handle.net/11427/34504en_ZA
dc.identifier.chicagocitationPohl, B, Y Richard, and N Fauchereau "Influence of the Madden–Julian Oscillation on Southern African Summer Rainfall." <i>Journal of Climate</i> 20, 16. (2007): 4227 - 4242. http://hdl.handle.net/11427/34504en_ZA
dc.identifier.citationPohl, B., Richard, Y. & Fauchereau, N. 2007. Influence of the Madden–Julian Oscillation on Southern African Summer Rainfall. <i>Journal of Climate.</i> 20(16):4227 - 4242. http://hdl.handle.net/11427/34504en_ZA
dc.identifier.issn0894-8755
dc.identifier.issn1520-0442
dc.identifier.ris TY - Journal Article AU - Pohl, B AU - Richard, Y AU - Fauchereau, N AB - Composite maps of outgoing longwave radiation (OLR) anomalies over the Madden-Julian oscillation (MJO) cycle show marked intraseasonal fluctuations over southern Africa (south of 15°S). Large-scale convective clusters are seen to propagate eastward and then northward over the continent, mainly between 10° and 20°S. The corresponding response of the rainfall field presents the alternation, over the cycle, of dry and humid phases, which are both significant. Moisture flux anomalies indicate an intraseasonal modulation of the midtropospheric easterly flow over the Congo basin at 700 hPa; these fluctuations are coupled to meridional flux anomalies that extend from the tropical to the subtropical austral latitudes, and favor occurrences of wet or dry conditions over the domain. Though statistically significant, the influence of the MJO on southern Africa is however not homogeneous spatially, and only the tropical areas exhibit sharp periodicities in the 30-60-day period range. The OLR dipole observed in previous studies at the interannual and synoptic time scales between the hinterland parts of southern Africa and the southwestern Indian Ocean in the north of Madagascar is investigated next, as it also shows strong fluctuations at the intraseasonal time scale. The study points out that the dipole is partly influenced by the MJO, though the strongest periodicities are found for slightly longer periods (35-80 days) than those typically associated with the oscillation. The forcing of the MJO on the OLR dipole, though significant, remains thus partial. DA - 2007 DB - OpenUCT DP - University of Cape Town IS - 16 J1 - Journal of Climate LK - https://open.uct.ac.za PY - 2007 SM - 0894-8755 SM - 1520-0442 T1 - Influence of the Madden–Julian Oscillation on Southern African Summer Rainfall TI - Influence of the Madden–Julian Oscillation on Southern African Summer Rainfall UR - http://hdl.handle.net/11427/34504 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/34504
dc.identifier.vancouvercitationPohl B, Richard Y, Fauchereau N. Influence of the Madden–Julian Oscillation on Southern African Summer Rainfall. Journal of Climate. 2007;20(16):4227 - 4242. http://hdl.handle.net/11427/34504.en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Oceanography
dc.publisher.facultyFaculty of Science
dc.sourceJournal of Climate
dc.source.journalissue16
dc.source.journalvolume20
dc.source.pagination4227 - 4242
dc.source.urihttps://dx.doi.org/10.1175/JCLI4231.1
dc.subject.otherDynamical climatology
dc.subject.otherTriggering
dc.subject.othermechanism
dc.subject.otherInterannual variation
dc.subject.otherAtmospheric convection
dc.subject.otherAtmospheric dynamics
dc.subject.otherMadden Julian oscillation
dc.subject.otherIntraseasonal variation
dc.subject.otherSummer
dc.subject.otherrainfall
dc.subject.otheratmospheric precipitation
dc.subject.othersubtropical zone
dc.subject.othertropical zone
dc.subject.otherHydroclimatology
dc.subject.otherClimate variability
dc.subject.otherOutgoing longwave radiation
dc.subject.otherComposite analysis
dc.subject.otherSouthern Africa
dc.subject.otherAfrica
dc.subject.otherClimatologie dynamique
dc.subject.otherDéclenchement
dc.subject.otherMécanisme
dc.subject.otherVariation interannuelle
dc.subject.otherConvection atmosphérique
dc.titleInfluence of the Madden–Julian Oscillation on Southern African Summer Rainfall
dc.typeJournal Article
uct.type.publicationResearch
uct.type.resourceJournal Article
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