Interannual variability of seasonal rainfall over the Cape south coast of South Africa and synoptic type association
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- 作者：Christien J. Engelbrecht ; Willem A. Landman
- 刊名：Climate Dynamics
- 出版年：2016
- 出版时间：July 2016
- 年：2016
- 卷：47
- 期：1-2
- 页码：295-313
- 全文大小：5,243 KB
- 刊物类别：Earth and Environmental Science
- 刊物主题：Earth sciences
Geophysics and Geodesy
Meteorology and Climatology
Oceanography - 出版者：Springer Berlin / Heidelberg
- ISSN：1432-0894
- 卷排序：47
文摘
The link between interannual variability of seasonal rainfall over the Cape south coast of South Africa and different synoptic types as well as selected teleconnections is explored. Synoptic circulation over the region is classified into different synoptic types by employing a clustering technique, the self-organizing map (SOM), on daily circulation data for the 33-year period from 1979 to 2011. Daily rainfall data are used to investigate interannual variability of seasonal rainfall within the context of the identified synoptic types. The anomalous frequency of occurrence of the different synoptic types for wet and for dry seasons differs significantly within the SOM space, except for austral spring. The main rainfall-producing synoptic types are to a large extent consistent for wet and dry seasons. The main rainfall-producing synoptic types have a notable larger contribution to seasonal rainfall totals during wet seasons than during dry seasons, consistent with a higher frequency of occurrence of the main rainfall-producing synoptic types during wet seasons compared to dry seasons. Dry seasons are characterized by a smaller contribution to seasonal rainfall totals by all the different synoptic types, but with the largest negative anomalies associated with low frequencies of the main rainfall-producing synoptic types. The frequencies of occurrence of specific configurations of ridging high pressure systems, cut-off lows and tropical-temperate troughs associated with rainfall are positively linked to interannual variability of seasonal rainfall. It is also shown that the distribution of synoptic types within the SOM space is linked to the Southern Annular Mode and El Niño Southern Oscillation, implying some predictability of intraseasonal variability at the seasonal time scale.KeywordsCape south coast of South AfricaSynoptic typesInterannual rainfall variabilityEl Niño Southern OscillationSouthern Annular ModeIntraseasonal predictability