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Climate Dynamics

, Volume 47, Issue 1–2, pp 295–313 | Cite as

Interannual variability of seasonal rainfall over the Cape south coast of South Africa and synoptic type association

  • Christien J. EngelbrechtEmail author
  • Willem A. Landman
Article

Abstract

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.

Keywords

Cape south coast of South Africa Synoptic types Interannual rainfall variability El Niño Southern Oscillation Southern Annular Mode Intraseasonal predictability 

Notes

Acknowledgments

Constructive comments from three anonymous reviewers improved the manuscript. This research was funded by the Water Research Commission (Project K5/2257/1) and the Applied Centre for Climate and Earth System Studies (ACCESS). Rainfall data were supplied by the South African Weather Service. Support for this study by the Agricultural Research Council and editorial contributions by Dr. Thomas Fyfield is greatly acknowledged. General discussions with Drs. L. Dyson, J. Malherbe and F. Engelbrecht are appreciated.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Christien J. Engelbrecht
    • 1
    • 2
    Email author
  • Willem A. Landman
    • 2
    • 3
  1. 1.Institute for Soil, Climate and WaterAgricultural Research CouncilPretoriaSouth Africa
  2. 2.Department of Geography, Geoinformatics and MeteorologyUniversity of PretoriaPretoriaSouth Africa
  3. 3.Climate Studies, Modelling and Environmental HealthCSIR Natural Resources and EnvironmentPretoriaSouth Africa

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