Synoptic Kelvin type perturbation waves over Congo basin over the period 1979–2010

The synoptic structure and inter-annual variability of Kelvin waves over the Congo basin from 1979 to 2010 are explored using outgoing longwave radiation (OLR) and National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis data. Composite method sho...

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Bibliographic Details
Published in:Journal of atmospheric and solar-terrestrial physics 2015-08, Vol.130-131, p.43-56
Main Authors: Sinclaire, Zebaze, Lenouo, André, Tchawoua, Clément, Janicot, Serge
Format: Article
Language:English
Subjects:
3–10 Days variability
Atmospherics
Basins
Congo basin
Convection
Geophysics
Kelvin waves
Low level
Perturbation methods
Physics
Precipitation
Surface chemistry
Time series
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Summary:The synoptic structure and inter-annual variability of Kelvin waves over the Congo basin from 1979 to 2010 are explored using outgoing longwave radiation (OLR) and National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis data. Composite method shows that high values of synoptic Kelvin wave (SKW) index are located over Congo basin during March–June where the convective active phase favours the formation of convective synoptic systems. Mean composite SKWs structure shows that these waves propagate faster over land surface and dissipate with suppressed phase. Because convective instability is smaller, these waves cannot grow in Congo basin. High correlation between SKWs and precipitation time series occurs when the Kelvin waves lead the precipitation time series by about 4 days. The analysis of 32 years datasets (1979–2010) also shows that in some particular year, strong SKWs propagation exists with periods centred around 5 days. Otherwise, results show marked inter-annual variability of Kelvin wave activity over Congo basin associated with divergence and low level westerly trade winds. •Synoptic structure and variability of Kelvin waves over the Congo basin are explored.•Mechanism responsible for the origin of the 3–10-day oscillation was used.•The convective active phase favours the formation of convective synoptic systems.•Synoptic Kelvin wave activity is correlated with 3–10 day precipitation anomalies.•Convectively active phase is coupled to atmospheric equatorial Kelvin wave.
ISSN:1364-6826
1879-1824
DOI:10.1016/j.jastp.2015.04.015