submitted to Journal of Climate
A k-means cluster analysis is used to summarize unfiltered daily atmospheric variability at regional-scale over the western Sahel and eastern tropical North Atlantic during the boreal summer season (July—September) 1961—1998. It employs zonal and meridional regional wind fields at 925, 700 and 200 h...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2006
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.380.7660 http://iri.columbia.edu/~awr/papers/Moron_Senegal_version4_part1.pdf |
| Summary: | A k-means cluster analysis is used to summarize unfiltered daily atmospheric variability at regional-scale over the western Sahel and eastern tropical North Atlantic during the boreal summer season (July—September) 1961—1998. It employs zonal and meridional regional wind fields at 925, 700 and 200 hPa from the European Centre for Medium Weather Forecast Reanalyses (ERA-40). An 8-cluster solution is shown to yield an integrated view of the complex regional circulation variability, without the need for explicit time filtering. Five of the weather types identified characterize typical phases of African easterly waves persistent monsoon surges, while the three others describe different stages of the seasonal cycle. Their temporal sequencing describes a systematic monsoonal evolution, together with considerable variability at subseasonal and inter-annual time scales. Daily rainfall occurrence at 13 gauge stations in Senegal is found to be moderately wellconditioned by the 8 weather types, with positive rainfall anomalies usually associated with lowlevel southerly wind anomalies. Interannual variability of daily rainfall frequency is shown to depend substantially on the frequency of occurrence of weather types specific to the beginning |
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