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Article Type:
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Paramount Impact of the Indian Ocean Dipole on the East African Short Rains: A CGCM Study

Swadhin K. Behera Frontier Research Center for Global Change/JAMSTEC, Yokohama, Japan

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Jing-Jia Luo Frontier Research Center for Global Change/JAMSTEC, Yokohama, Japan

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Sebastien Masson Frontier Research Center for Global Change/JAMSTEC, Yokohama, Japan

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Pascale Delecluse Laboratoire d’Océanographie Dynamique et de Climatologie, Paris, and Laboratoire des Sciences du Climat et de l’Environnement, Orme, France

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Silvio Gualdi Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy

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Antonio Navarra Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy

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Toshio Yamagata Department of Earth and Planetary Science, University of Tokyo, Tokyo, and Frontier Research Center for Global Change/JAMSTEC, Yokohama, Japan

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Print Publication:
01 Nov 2005
DOI:
https://doi.org/10.1175/JCLI3541.1
Page(s):
4514–4530
Restricted access

Abstract

The variability in the East African short rains is investigated using 41-yr data from the observation and 200-yr data from a coupled general circulation model known as the Scale Interaction Experiment-Frontier Research Center for Global Change, version 1 (SINTEX-F1). The model-simulated data provide a scope to understand the climate variability in the region with a better statistical confidence. Most of the variability in the model short rains is linked to the basinwide large-scale coupled mode, that is, the Indian Ocean dipole (IOD) in the tropical Indian Ocean. The analysis of observed data and model results reveals that the influence of the IOD on short rains is overwhelming as compared to that of the El Niño–Southern Oscillation (ENSO); the correlation between ENSO and short rains is insignificant when the IOD influence is excluded. The IOD–short rains relationship does not change significantly in a model experiment in which the ENSO influence is removed by decoupling the ocean and atmosphere in the tropical Pacific. The partial correlation analysis of the model data demonstrates that a secondary influence comes from a regional mode located near the African coast.

Inconsistent with the observational findings, the model results show a steady evolution of IOD prior to extreme events of short rains. Dynamically consistent evolution of correlations is found in anomalies of the surface winds, currents, sea surface height, and sea surface temperature. Anomalous changes of the Walker circulation provide a necessary driving mechanism for anomalous moisture transport and convection over the coastal East Africa. The model results nicely augment the observational findings and provide us with a physical basis to consider IOD as a predictor for variations of the short rains. This is demonstrated in detail using the statistical analysis method. The prediction skill of the dipole mode SST index in July and August is 92% for the observation, which scales slightly higher for the model index (96%) in August. As observed in data, the model results show decadal weakening in the relationship between IOD and short rains owing to weakening in the IOD activity.

Corresponding author address: Toshio Yamagata, Frontier Research Center for Global Change/JAMSTEC, Showa-machi, Yokohama, Kanagawa 236-0001, Japan. Email: yamagata@eps.s.u-tokyo.ac.jp

Abstract

The variability in the East African short rains is investigated using 41-yr data from the observation and 200-yr data from a coupled general circulation model known as the Scale Interaction Experiment-Frontier Research Center for Global Change, version 1 (SINTEX-F1). The model-simulated data provide a scope to understand the climate variability in the region with a better statistical confidence. Most of the variability in the model short rains is linked to the basinwide large-scale coupled mode, that is, the Indian Ocean dipole (IOD) in the tropical Indian Ocean. The analysis of observed data and model results reveals that the influence of the IOD on short rains is overwhelming as compared to that of the El Niño–Southern Oscillation (ENSO); the correlation between ENSO and short rains is insignificant when the IOD influence is excluded. The IOD–short rains relationship does not change significantly in a model experiment in which the ENSO influence is removed by decoupling the ocean and atmosphere in the tropical Pacific. The partial correlation analysis of the model data demonstrates that a secondary influence comes from a regional mode located near the African coast.

Inconsistent with the observational findings, the model results show a steady evolution of IOD prior to extreme events of short rains. Dynamically consistent evolution of correlations is found in anomalies of the surface winds, currents, sea surface height, and sea surface temperature. Anomalous changes of the Walker circulation provide a necessary driving mechanism for anomalous moisture transport and convection over the coastal East Africa. The model results nicely augment the observational findings and provide us with a physical basis to consider IOD as a predictor for variations of the short rains. This is demonstrated in detail using the statistical analysis method. The prediction skill of the dipole mode SST index in July and August is 92% for the observation, which scales slightly higher for the model index (96%) in August. As observed in data, the model results show decadal weakening in the relationship between IOD and short rains owing to weakening in the IOD activity.

Corresponding author address: Toshio Yamagata, Frontier Research Center for Global Change/JAMSTEC, Showa-machi, Yokohama, Kanagawa 236-0001, Japan. Email: yamagata@eps.s.u-tokyo.ac.jp

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  • Allan, R., and Coauthors, 2001: Is there an Indian Ocean dipole, and is it independent of the El Niño–Southern Oscillation? CLIVAR Exchanges, Vol. 6, 18–22.

    • Search Google Scholar
    • Export Citation

  • Anderson, D. L. T., 1999: Extremes in the Indian Ocean. Nature, 401 , 337–338.

  • Ashok, K., Z. Guan, and T. Yamagata, 2001: Impact of the Indian Ocean dipole on the decadal relationship between the Indian monsoon rainfall and ENSO. Geophys. Res. Lett., 28 , 4499–4502.

    • Search Google Scholar
    • Export Citation

  • Ashok, K., W. Chan, T. Motoi, and T. Yamagata, 2004: Decadal variability of the Indian Ocean dipole. Geophys. Res. Lett., 31 .L24207, doi:10.1029/2004GL021345.

    • Search Google Scholar
    • Export Citation

  • Baquero-Bernal, A., M. Latif, and S. Legutke, 2002: On dipole-like variability in the tropical Indian Ocean. J. Climate, 15 , 1358–1368.

    • Search Google Scholar
    • Export Citation

  • Behera, S. K., and T. Yamagata, 2003: Influence of the Indian Ocean dipole on the Southern Oscillation. J. Meteor. Soc. Japan, 81 , l69–177.

    • Search Google Scholar
    • Export Citation

  • Behera, S. K., R. Krishnan, and T. Yamagata, 1999: Unusual ocean–atmosphere conditions in the tropical Indian Ocean during 1994. Geophys. Res. Lett., 26 , 3001–3004.

    • Search Google Scholar
    • Export Citation

  • Behera, S. K., J-J. Luo, S. Masson, T. Yamagata, P. Delecluse, S. Gualdi, and A. Navarra, 2003a: Impact of the Indian Ocean dipole on the East African short rains: A CGCM study. CLIVAR Exchanges, Vol. 27, 43–45.

    • Search Google Scholar
    • Export Citation

  • Behera, S. K., S. A. Rao, H. N. Saji, and T. Yamagata, 2003b: Comments on “A cautionary note on the interpretation of EOFs.”. J. Climate, 16 , 1087–1093.

    • Search Google Scholar
    • Export Citation

  • Bjerknes, J., 1969: Atmospheric teleconnections from the equatorial Pacific. Mon. Wea. Rev., 97 , 163–172.

  • Black, E., J. Slingo, and K. R. Sperber, 2003: An observational study of the relationship between excessively strong short rains in coastal East Africa and Indian Ocean SST. Mon. Wea. Rev., 131 , 74–94.

    • Search Google Scholar
    • Export Citation

  • Carton, J. A., G. Chepurin, X. Cao, and B. S. Giese, 2000: A simple ocean data assimilation analysis of the global upper ocean 1950–1995. Part 1: Methodology. J. Phys. Oceanogr., 30 , 294–309.

    • Search Google Scholar
    • Export Citation

  • Clark, C. O., P. J. Webster, and J. E. Cole, 2003: Interdecadal variability of the relationship between the Indian Ocean zonal mode and East African coastal rainfall anomalies. J. Climate, 16 , 548–554.

    • Search Google Scholar
    • Export Citation

  • CLIVAR Africa Report, 1999: Climate research for Africa. WCRP Informal Rep. 16/1999, ICPO Publication Series 29, 79 pp.

  • Feng, M., G. Meyers, and S. Wijffels, 2001: Interannual upper ocean variability in the tropical Indian Ocean. Geophys. Res. Lett., 28 , 4151–4154.

    • Search Google Scholar
    • Export Citation

  • Gualdi, S., E. Guilyardi, A. Navarra, S. Masina, and P. Delecluse, 2003: The interannual variability in the tropical Indian Ocean as simulated by a CGCM. Climate Dyn., 20 , 567–582.

    • Search Google Scholar
    • Export Citation

  • Guan, Z., and T. Yamagata, 2003: The unusual summer of 1994 in East Asia: IOD teleconnections. Geophys. Res. Lett., 30 .1544, doi:10.1029/2002GL016831.

    • Search Google Scholar
    • Export Citation

  • Guilyardi, E., G. Madec, and L. Terray, 2001: The role of lateral ocean physics in the upper ocean thermal balance of a coupled ocean–atmosphere GCM. Climate Dyn., 17 , 589–599.

    • Search Google Scholar
    • Export Citation

  • Hastenrath, S., and D. Polzin, 2003: Circulation mechanisms of climate anomalies in the equatorial Indian Ocean. Meteor. Z., 12 , 81–93.

    • Search Google Scholar
    • Export Citation

  • Hastenrath, S., A. Nicklis, and L. Greischar, 1993: Atmospheric–hydrospheric mechanisms of climate anomalies in the western equatorial Indian Ocean. J. Geophys. Res., 98 , 20219–20235.

    • Search Google Scholar
    • Export Citation

  • Iizuka, S., T. Matsuura, and T. Yamagata, 2000: The Indian Ocean SST dipole simulated in a coupled general circulation model. Geophys. Res. Lett., 27 , 3369–3372.

    • Search Google Scholar
    • Export Citation

  • Jury, R. M., 2002: Economic impacts of climate variability in South Africa and development of resource prediction models. J. Appl. Meteor., 41 , 46–55.

    • Search Google Scholar
    • Export Citation

  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77 , 437–471.

  • Lau, N-C., and M. J. Nath, 2004: Coupled GCM simulation of atmosphere–ocean variability associated with zonally asymmetric SST changes in the tropical Indian Ocean. J. Climate, 17 , 245–265.

    • Search Google Scholar
    • Export Citation

  • Legates, D. R., and C. J. Willmott, 1990: Mean seasonal and spatial variability in gauge-corrected, global precipitation. Int. J. Climatol., 10 , 111–127.

    • Search Google Scholar
    • Export Citation

  • Luo, J-J., S. Masson, S. Behera, P. Delecluse, S. Gualdi, A. Navarra, and T. Yamagata, 2003: South Pacific origin of the decadal ENSO-like variation as simulated by a coupled GCM. Geophys. Res. Lett., 30 .2250, doi:10.1029/2003GL018649.

    • Search Google Scholar
    • Export Citation

  • Madec, G., P. Delecluse, M. Imbard, and C. Levy, 1998: OPA version 8.1 ocean general circulation model reference manual. Tech. Rep./Note 11, LODYC/IPSL, 91 pp.

  • Masson, S., and Coauthors, 2005: Impact of barrier layer on winter–spring variability of the southeastern Arabian Sea. Geophys. Res. Lett., 32 .L07703, doi:10.1029/2004GL021980.

    • Search Google Scholar
    • Export Citation

  • Morse, A. P., M. B. Hoshen, F. D. Reyes, and M. C. Thomson, 2003: Towards forecasting epidemics in Africa—The use of seasonal forecasting. CLIVAR Exchanges, Vol. 27, 50–52.

    • Search Google Scholar
    • Export Citation

  • Murtugudde, R. G., J. P. McCreary, and A. J. Busalacchi, 2000: Oceanic processes associated with anomalous events in the Indian Ocean with relevance to 1997–1998. J. Geophys. Res., 105 , 3295–3306.

    • Search Google Scholar
    • Export Citation

  • Mutai, C. C., and M. N. Ward, 2000: East African rainfall and the tropical circulation/convection on intraseasonal to interannual time scales. J. Climate, 13 , 3915–3939.

    • Search Google Scholar
    • Export Citation

  • Ogallo, L. J., 1988: Relationship between seasonal rainfall in East Africa and the Southern Oscillation. J. Climatol., 8 , 31–43.

  • Ogallo, L. J., J. E. Janowiak, and M. S. Halpert, 1988: Teleconnection between seasonal rainfall over East Africa and global surface temperature anomalies. J. Meteor. Soc. Japan, 66 , 807–821.

    • Search Google Scholar
    • Export Citation

  • Philippon, N., P. Camberlin, and N. Fauchereau, 2002: Empirical predictability study of October–December East African rainfall. Quart. J. Roy. Meteor. Soc., 128 , 2239–2256.

    • Search Google Scholar
    • Export Citation

  • Rao, S. A., and T. Yamagata, 2004: Abrupt termination of Indian Ocean dipole events in response to intraseasonal disturbances. Geophys. Res. Lett., 31 .L19306, doi:10.1029/2004GL020842.

    • Search Google Scholar
    • Export Citation

  • Rao, S. A., and S. K. Behera, 2005: Subsurface influence on SST in the tropical Indian Ocean structure and interactions. Dyn. Atmos. Ocean, 39 , 103–135.

    • Search Google Scholar
    • Export Citation

  • Rao, S. A., S. K. Behera, Y. Masumoto, and T. Yamagata, 2002: Interannual variability in the subsurface tropical Indian Ocean with a special emphasis on the Indian Ocean dipole. Deep-Sea Res., 49B , 1549–1572.

    • Search Google Scholar
    • Export Citation

  • Rayner, N. A., E. B. Horton, D. E. Parker, C. K. Folland, and R. B. Hackett, 1996: Version 2.2 of the Global Sea-Ice and Sea Surface Temperature data set, 1903–1994. Climate Research Tech. Note 74, U.K. Met Office, 21 pp.

  • Reverdin, G., D. L. Cadet, and D. Gutzler, 1986: Interannual displacements of convection and surface circulation over the equatorial Indian Ocean. Quart. J. Roy. Meteor. Soc., 112 , 43–67.

    • Search Google Scholar
    • Export Citation

  • Roeckner, E., and Coauthors, 1996: The atmospheric general circulation model ECHAM4: Model description and simulation of present day climate. Max-Plank-Institut für Meteorologie Rep. 218, Hamburg, Germany, 90 pp.

  • Ropelewski, F., and M. S. Halpert, 1987: Global and regional scale precipitation patterns associated with the El Niño/Southern Oscillation. Mon. Wea. Rev., 115 , 1602–1626.

    • Search Google Scholar
    • Export Citation

  • Saji, H. N., and T. Yamagata, 2003a: Structure of SST and surface wind variability in COADS observations during IOD years. J. Climate, 16 , 2735–2751.

    • Search Google Scholar
    • Export Citation

  • Saji, N. H., and T. Yamagata, 2003b: Interference of teleconnection patterns generated from the tropical Indian and Pacific Oceans. Climate Res., 25 , 151–169.

    • Search Google Scholar
    • Export Citation

  • Saji, N. H., B. N. Goswami, P. N. Vinayachandran, and T. Yamagata, 1999: A dipole mode in the tropical Indian Ocean. Nature, 401 , 360–363.

    • Search Google Scholar
    • Export Citation

  • Shinoda, T., M. A. Alexander, and H. H. Hendon, 2004: Remote response of the Indian Ocean to interannual SST variations in the tropical Pacific. J. Climate, 17 , 362–372.

    • Search Google Scholar
    • Export Citation

  • Tozuka, T., and T. Yamagata, 2003: Annual ENSO. J. Phys. Oceanogr., 33 , 1564–1578.

  • Valcke, S., L. Terray, and A. Piacentini, 2000: The OASIS coupler user guide version 2.4. Tech. Rep. TR/CMGC/00-10, CERFACS, Toulouse, France, 85 pp.

  • Vinayachandran, P. N., N. H. Saji, and T. Yamagata, 1999: Response of the equatorial Indian Ocean to an anomalous wind event during 1994. Geophys. Res. Lett., 26 , 1613–1616.

    • Search Google Scholar
    • Export Citation

  • Webster, P. J., A. Moore, J. Loschnigg, and M. Leban, 1999: Coupled ocean–atmosphere dynamics in the Indian Ocean during 1997–98. Nature, 401 , 356–360.

    • Search Google Scholar
    • Export Citation

  • Willmott, C. J., and K. Matsuura, 1995: Smart interpolation of annually averaged air temperature in the United States. J. Appl. Meteor., 34 , 2557–2586.

    • Search Google Scholar
    • Export Citation

  • Xie, S-P., H. Annamalai, F. Schott, and J. P. McCreary, 2002: Structure and mechanisms of south Indian Ocean climate variability. J. Climate, 15 , 864–878.

    • Search Google Scholar
    • Export Citation

  • Yamagata, T., S. K. Behera, S. A. Rao, Z. Guan, K. Ashok, and H. N. Saji, 2002: The Indian Ocean dipole: A physical entity. CLIVAR Exchanges, Vol. 24, 15–18.

    • Search Google Scholar
    • Export Citation

  • Yamagata, T., S. K. Behera, S. A. Rao, Z. Guan, K. Ashok, and H. N. Saji, 2003: Comments on “Dipoles, temperature gradient, and tropical climate anomalies.”. Bull. Amer. Meteor. Soc., 84 , 1418–1422.

    • Search Google Scholar
    • Export Citation

  • Yamagata, T., S. K. Behera, J-J. Luo, S. Masson, M. Jury, and S. A. Rao, 2004: Coupled ocean–atmosphere variability in the tropical Indian Ocean. Earth Climate: The Ocean–Atmosphere Interaction, Geophys. Monogr., No. 147, Amer. Geophys. Union, 189–212.

  • Yu, J-Y., and K. M. Lau, 2004: Contrasting Indian Ocean SST variability with and without ENSO influence: A coupled atmosphere–ocean GCM study. Meteor. Atmos. Phys., doi:10.1007/s00703-00400094-7.

    • Search Google Scholar
    • Export Citation

  • Yule, G. U., 1907: On the theory of correlation for any number of variables treated by a new system of notation. Proc. Roy. Soc., 79A , 182–193.

    • Search Google Scholar
    • Export Citation

  • Zubair, L., S. A. Rao, and T. Yamagata, 2003: Modulation of Sri Lankan Maha rainfall by the Indian Ocean dipole. Geophys. Res. Lett., 30 .1063, doi:10.1029/2002GL015639.

    • Search Google Scholar
    • Export Citation
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