The impact of ENSO on Southern African rainfall in CMIP5 ocean atmosphere coupled climate models

Bastien Dieppois, M. Rouault, M. New

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    Abstract

    We study the ability of 24 ocean atmosphere global coupled models from the Coupled Model Intercomparison Project 5 (CMIP5) to reproduce the teleconnections between El Niño Southern Oscillation (ENSO) and Southern African rainfall in austral summer using historical forced simulations, with a focus on the atmospheric dynamic associated with El Niño. Overestimations of summer rainfall occur over Southern Africa in all CMIP5 models. Abnormal westward extensions of ENSO patterns are a common feature of all CMIP5 models, while the warming of the Indian Ocean that happens during El Niño is not correctly reproduced. This could impact the teleconnection between ENSO and Southern African rainfall which is represented with mixed success in CMIP5 models. Large-scale anomalies of suppressed deep-convection over the tropical maritime continent and enhanced convection from the central to eastern Pacific are correctly simulated. However, regional biases occur above Africa and the Indian Ocean, particularly in the position of the deep convection anomalies associated with El Niño, which can lead to the wrong sign in rainfall anomalies in the northwest part of South Africa. From the near-surface to mid-troposphere, CMIP5 models underestimate the observed anomalous pattern of pressure occurring over Southern Africa that leads to dry conditions during El Niño years.
    Original languageEnglish
    Pages (from-to)2425-2442
    JournalClimate Dynamics
    Volume45
    Issue number9
    DOIs
    Publication statusPublished - Jan 2015

    Bibliographical note

    The final publication is available at Springer via http://dx.doi.org/10.1007/s00382-015-2480-x

    Keywords

    • Southern Africa
    • Rainfall
    • El Niño Southern Oscillation (ENSO)
    • Coupled model
    • CMIP5
    • Teleconnection

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