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Communication incl. Poster: BibTeX citation key:  Gueyea
Gueye, A. K., Janicot, S., Niang, A., Sawadogo, S., Sultan, B., Diongue-Niang, A. & Thiria, S. 2009. Synoptic climatology over Senegal during the summer monsoon season with Self-Organizing Maps. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: Devic 2009-10-12 10:41:04    Last Edited by: roussot 2009-10-16 16:31:34
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Categories: General
Keywords: Precipitation
Creators: Diongue-Niang, Gueye, Janicot, Niang, Sawadogo, Sultan, Thiria
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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Abstract
The aim of this work is to define the main synoptic weather regimes relevant for understanding the daily variability of rainfall during the summer monsoon season over Senegal. “Pure” synoptic weather regimes have been defined by removing the influence of seasonal and interannual time scales, in order to highlight the day by day variability of the atmospheric circulation. The Self-Organizing Maps approach, an efficient clustering methodology based on non-linear artificial neural network, has been applied to compute these regimes. Nine weather regimes have been highlighted using the mean sea level pressure and 850 hPa wind field as variables. Two of them represent the classical 3-5-day African easterly waves with a mean wavelength of about 3000 kilometres. Three others are characterized by a modulation of the semi-permanent trough located along the western coast of West Africa and might be interpreted in terms of the 6-9-day easterly waves, located more to the north than the 3-5-day easterly waves. The last four weather regimes are characterized by a more or less strong north-south or south-north dipole of circulation. They can be interpreted as a northward/southward displacement of the Saharan depression for two of them, and a filling/deepening of this depression for the other two. The circulation patterns of all these nine weather regimes are very consistent with the associated anomaly patterns of precipitable water height, mid-troposphere vertical velocity, and outgoing longwave radiation, as well as with rainfall distribution and rainfall extremes over the Senegal. These weather regimes can provide useful information for estimating daily rainfall amounts at a local scale.
Last Edited by: roussot