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Comparison of simulated and reconstructed variations in East African hydroclimate over the last millennium

(2016) CLIMATE OF THE PAST. 12(7). p.1499-1518
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Abstract
The multi-decadal to centennial hydroclimate changes in East Africa over the last millennium are studied by comparing the results of forced transient simulations by six general circulation models (GCMs) with published hydroclimate reconstructions from four lakes: Challa and Naivasha in equatorial East Africa, and Masoko and Malawi in southeastern inter-tropical Africa. All GCMs simulate fairly well the unimodal seasonal cycle of precipitation in the Masoko-Malawi region, while the bimodal seasonal cycle characterizing the Challa-Naivasha region is generally less well captured by most models. Model results and lake-based hydroclimate reconstructions display very different temporal patterns over the last millennium. Additionally, there is no common signal among the model time series, at least until 1850. This suggests that simulated hydroclimate fluctuations are mostly driven by internal variability rather than by common external forcing. After 1850, half of the models simulate a relatively clear response to forcing, but this response is different between the models. Overall, the link between precipitation and tropical sea surface temperatures (SSTs) over the pre-industrial portion of the last millennium is stronger and more robust for the Challa-Naivasha region than for theMasoko-Malawi region. At the inter-annual timescale, last-millennium Challa-Naivasha precipitation is positively (negatively) correlated with western (eastern) Indian Ocean SST, while the influence of the Pacific Ocean appears weak and unclear. Although most often not significant, the same pattern of correlations between East African rainfall and the Indian Ocean SST is still visible when using the last-millennium time series smoothed to highlight centennial variability, but only in fixed-forcing simulations. This means that, at the centennial timescale, the effect of (natural) climate forcing can mask the imprint of internal climate variability in large-scale teleconnections.
Keywords
CLIMATE FORCING RECONSTRUCTIONS, INDIAN-OCEAN, RAINFALL ANOMALIES, GAUGE OBSERVATIONS, REGIONAL CLIMATE, PMIP SIMULATIONS, SOUTHERN AFRICA, SYSTEM MODEL, LAKE MASOKO, LONG RAINS

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Citation

Please use this url to cite or link to this publication:

MLA
Klein, François et al. “Comparison of Simulated and Reconstructed Variations in East African Hydroclimate over the Last Millennium.” CLIMATE OF THE PAST 12.7 (2016): 1499–1518. Print.
APA
Klein, F., Goosse, H., Graham, N. E., & Verschuren, D. (2016). Comparison of simulated and reconstructed variations in East African hydroclimate over the last millennium. CLIMATE OF THE PAST, 12(7), 1499–1518.
Chicago author-date
Klein, François, Hugues Goosse, Nicholas E Graham, and Dirk Verschuren. 2016. “Comparison of Simulated and Reconstructed Variations in East African Hydroclimate over the Last Millennium.” Climate of the Past 12 (7): 1499–1518.
Chicago author-date (all authors)
Klein, François, Hugues Goosse, Nicholas E Graham, and Dirk Verschuren. 2016. “Comparison of Simulated and Reconstructed Variations in East African Hydroclimate over the Last Millennium.” Climate of the Past 12 (7): 1499–1518.
Vancouver
1.
Klein F, Goosse H, Graham NE, Verschuren D. Comparison of simulated and reconstructed variations in East African hydroclimate over the last millennium. CLIMATE OF THE PAST. 2016;12(7):1499–518.
IEEE
[1]
F. Klein, H. Goosse, N. E. Graham, and D. Verschuren, “Comparison of simulated and reconstructed variations in East African hydroclimate over the last millennium,” CLIMATE OF THE PAST, vol. 12, no. 7, pp. 1499–1518, 2016.
@article{8519503,
  abstract     = {The multi-decadal to centennial hydroclimate changes in East Africa over the last millennium are studied by comparing the results of forced transient simulations by six general circulation models (GCMs) with published hydroclimate reconstructions from four lakes: Challa and Naivasha in equatorial East Africa, and Masoko and Malawi in southeastern inter-tropical Africa. All GCMs simulate fairly well the unimodal seasonal cycle of precipitation in the Masoko-Malawi region, while the bimodal seasonal cycle characterizing the Challa-Naivasha region is generally less well captured by most models. Model results and lake-based hydroclimate reconstructions display very different temporal patterns over the last millennium. Additionally, there is no common signal among the model time series, at least until 1850. This suggests that simulated hydroclimate fluctuations are mostly driven by internal variability rather than by common external forcing. After 1850, half of the models simulate a relatively clear response to forcing, but this response is different between the models. Overall, the link between precipitation and tropical sea surface temperatures (SSTs) over the pre-industrial portion of the last millennium is stronger and more robust for the Challa-Naivasha region than for theMasoko-Malawi region. At the inter-annual timescale, last-millennium Challa-Naivasha precipitation is positively (negatively) correlated with western (eastern) Indian Ocean SST, while the influence of the Pacific Ocean appears weak and unclear. Although most often not significant, the same pattern of correlations between East African rainfall and the Indian Ocean SST is still visible when using the last-millennium time series smoothed to highlight centennial variability, but only in fixed-forcing simulations. This means that, at the centennial timescale, the effect of (natural) climate forcing can mask the imprint of internal climate variability in large-scale teleconnections.},
  author       = {Klein, François and Goosse, Hugues and Graham, Nicholas E and Verschuren, Dirk},
  issn         = {1814-9332},
  journal      = {CLIMATE OF THE PAST},
  keywords     = {CLIMATE FORCING RECONSTRUCTIONS,INDIAN-OCEAN,RAINFALL ANOMALIES,GAUGE OBSERVATIONS,REGIONAL CLIMATE,PMIP SIMULATIONS,SOUTHERN AFRICA,SYSTEM MODEL,LAKE MASOKO,LONG RAINS},
  language     = {eng},
  number       = {7},
  pages        = {1499--1518},
  title        = {Comparison of simulated and reconstructed variations in East African hydroclimate over the last millennium},
  url          = {http://dx.doi.org/10.5194/cp-12-1499-2016},
  volume       = {12},
  year         = {2016},
}

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