Editorial Type:
Article
Article Type:
Research Article

Climate Adjustments over Africa Accompanying the Indian Monsoon Onset

P. Camberlin Centre de Recherches de Climatologie, UMR 5210 CNRS/uB, Université de Bourgogne, Dijon, France

Search for other papers by P. Camberlin in
Current site
Google Scholar
PubMed Close
,
B. Fontaine Centre de Recherches de Climatologie, UMR 5210 CNRS/uB, Université de Bourgogne, Dijon, France

Search for other papers by B. Fontaine in
Current site
Google Scholar
PubMed Close
,
S. Louvet HydroSciences Montpellier, UMR 5569, IRD/Université de Montpellier 2, Montpellier, France

Search for other papers by S. Louvet in
Current site
Google Scholar
PubMed Close
,
P. Oettli Centre de Recherches de Climatologie, UMR 5210 CNRS/uB, Université de Bourgogne, Dijon, and LOCEAN, UMR 7159 NRS/IRD/UPMC/MNHN, Université Pierre et Marie Curie, Paris, France

Search for other papers by P. Oettli in
Current site
Google Scholar
PubMed Close
, and
P. Valimba Department of Water Resources Engineering, College of Engineering and Technology, University of Dar es Salaam, Dar es Salaam, Tanzania

Search for other papers by P. Valimba in
Current site
Google Scholar
PubMed Close
Print Publication:
15 Apr 2010
DOI:
https://doi.org/10.1175/2009JCLI3302.1
Page(s):
2047–2064
Restricted access

Abstract

Rainfall and circulation changes accompanying the Indian monsoon onset are examined, focusing on the African continent and neighboring areas. The Indian Meteorological Department official monsoon onset dates over Kerala (MOK; on average on 1 June) are used. Composites are formed at a pentad (5 days) time scale to compare pre- and postonset conditions. Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) data for 1979–2007 indicate that a substantial rainfall decrease over several parts of Africa is associated with MOK. Significant rainfall anomalies, after removal of the mean seasonal cycle, are found in eastern Africa and the nearby western Indian Ocean. Indian monsoon onset dates over the period 1958–2001 are correlated at 0.55 with the cessation dates of the March–May rainy season (the long rains) averaged over Kenya and northern Tanzania. The rainy season cessation leads the onset by 12 days, on average. An early cessation of the March–May rains tends to precede an early onset over India. Over East Africa, the rainfall decrease is associated with a strengthening of the southerly winds (Somali jet) shortly before MOK, enhancing wind divergence and wind shear.

A weaker rainfall signal is noted over western Africa and the Gulf of Guinea. MOK coincides with a pause in the progression of the West African monsoon. The pause is associated with anomalous descent over the Sahel, culminating two to three pentads after MOK. Composite maps further indicate that MOK is followed over much of the African continent by a sea level pressure rise and, between India and North Africa, a westward propagation of easterly wind and positive geopotential height anomalies. Many of these signals are associated with Madden–Julian oscillations, but independent features, suggesting Rossby wave propagation over North Africa, are also found to connect MOK and West Africa. Overall, these results are indicative of a large-scale adjustment of the atmospheric dynamics across both eastern and western Africa in conjunction with the monsoon onset over India.

Corresponding author address: Pierre Camberlin, 6 Bd Gabriel, Centre de Recherches de Climatologie, UMR 5210 CNRS/uB, Université de Bourgogne, 21000 Dijon, France. Email: camber@u-bourgogne.fr

Abstract

Rainfall and circulation changes accompanying the Indian monsoon onset are examined, focusing on the African continent and neighboring areas. The Indian Meteorological Department official monsoon onset dates over Kerala (MOK; on average on 1 June) are used. Composites are formed at a pentad (5 days) time scale to compare pre- and postonset conditions. Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) data for 1979–2007 indicate that a substantial rainfall decrease over several parts of Africa is associated with MOK. Significant rainfall anomalies, after removal of the mean seasonal cycle, are found in eastern Africa and the nearby western Indian Ocean. Indian monsoon onset dates over the period 1958–2001 are correlated at 0.55 with the cessation dates of the March–May rainy season (the long rains) averaged over Kenya and northern Tanzania. The rainy season cessation leads the onset by 12 days, on average. An early cessation of the March–May rains tends to precede an early onset over India. Over East Africa, the rainfall decrease is associated with a strengthening of the southerly winds (Somali jet) shortly before MOK, enhancing wind divergence and wind shear.

A weaker rainfall signal is noted over western Africa and the Gulf of Guinea. MOK coincides with a pause in the progression of the West African monsoon. The pause is associated with anomalous descent over the Sahel, culminating two to three pentads after MOK. Composite maps further indicate that MOK is followed over much of the African continent by a sea level pressure rise and, between India and North Africa, a westward propagation of easterly wind and positive geopotential height anomalies. Many of these signals are associated with Madden–Julian oscillations, but independent features, suggesting Rossby wave propagation over North Africa, are also found to connect MOK and West Africa. Overall, these results are indicative of a large-scale adjustment of the atmospheric dynamics across both eastern and western Africa in conjunction with the monsoon onset over India.

Corresponding author address: Pierre Camberlin, 6 Bd Gabriel, Centre de Recherches de Climatologie, UMR 5210 CNRS/uB, Université de Bourgogne, 21000 Dijon, France. Email: camber@u-bourgogne.fr

Save
Cover Journal of Climate
Journal of Climate

  • Anantakrishnan, R., and M. K. Soman, 1988: The onset of the south-west monsoon over Kerala: 1901–1980. J. Climatol., 8 , 283–296.

  • Boos, W. R., and K. A. Emanuel, 2009: Annual intensification of the Somali jet in a quasi-equilibrium framework: Observational composites. Quart. J. Roy. Meteor. Soc., 135 , 319–335.

    • Search Google Scholar
    • Export Citation

  • Cadet, D. L., and M. Desbois, 1980: The burst of the 1978 Indian summer monsoon as seen from METEOSAT. Mon. Wea. Rev., 108 , 1697–1701.

    • Search Google Scholar
    • Export Citation

  • Camberlin, P., and O. Planchon, 1997: Coastal precipitation regimes in Kenya. Geogr. Ann., 79A , 1–2. 109–119.

  • Camberlin, P., and R. E. Okoola, 2003: The onset and cessation of the “long rains” in eastern Africa and their interannual variability. Theor. Appl. Climatol., 75 , 43–54.

    • Search Google Scholar
    • Export Citation

  • Chakraborty, A., R. S. Nanjundiah, and J. Srinivasan, 2008: Impact of African orography and the Indian summer monsoon on the low-level Somali jet. Int. J. Climatol., 29 , 983–992. doi:10.1002/joc.1720.

    • Search Google Scholar
    • Export Citation

  • Fasullo, J., and P. J. Webster, 2003: A hydrological definition of Indian monsoon onset and withdrawal. J. Climate, 16 , 3200–3211.

  • Findlater, J., 1969: A major low-level air current near the Indian Ocean during the northern summer. Quart. J. Roy. Meteor. Soc., 95 , 362–380.

    • Search Google Scholar
    • Export Citation

  • Findlater, J., 1974: The low-level cross-equatorial air current of the western Indian Ocean during the northern summer. Weather, 29 , 411–416.

    • Search Google Scholar
    • Export Citation

  • Findlater, J., 1978: Observational aspects of the low-level cross-equatorial jet stream. Monsoon Dynamics, T. N. Krishnamurti, Ed., Birkhäuser Verlag, 1251–1262.

    • Search Google Scholar
    • Export Citation

  • Flohn, H., 1957: Large-scale aspects of the “summer monsoon” in south and East Asia. J. Meteor. Soc. Japan, 35 , 180–186.

  • Fontaine, B., and S. Louvet, 2006: Sudan-Sahel rainfall onset: Definition of an objective index, types of years, and experimental hindcasts. J. Geophys. Res., 111 , D20103. doi:10.1029/2005JD007019.

    • Search Google Scholar
    • Export Citation

  • Fontaine, B., S. Louvet, and P. Roucou, 2008: Definition and predictability of an OLR-based West African monsoon onset. Int. J. Climatol., 28 , 1787–1798. doi:10.1002/joc.1674.

    • Search Google Scholar
    • Export Citation

  • Gill, A. E., 1980: Some simple solutions for heat-induced tropical circulation. Quart. J. Roy. Meteor. Soc., 106 , 447–462.

  • Hagos, S. M., and K. H. Cook, 2007: Dynamics of the West African monsoon jump. J. Climate, 20 , 5264–5284.

  • Hahn, D. G., and S. Manabe, 1975: The role of mountains in the South Asian monsoonal circulation. J. Atmos. Sci., 32 , 1515–1541.

  • Hart, J. E., 1977: On the theory of the East African low level jet stream. Pure Appl. Geophys., 115 , 1263–1282.

  • He, H., J. W. McGinnis, Z. Song, and M. Yanai, 1987: Onset of the Asian monsoon in 1979 and the effect of the Tibetan Plateau. Mon. Wea. Rev., 115 , 1966–1995.

    • Search Google Scholar
    • Export Citation

  • Hendon, H. H., and M. L. Salby, 1994: The life cycle of the Madden–Julian oscillation. J. Atmos. Sci., 51 , 2225–2237.

  • Janicot, S., 2009: A comparison of Indian and African monsoon variability at different time scales. C. R. Geosci., 351 , 575–590. doi:10.1016/j.crte.2009.02.002.

    • Search Google Scholar
    • Export Citation

  • Janicot, S., F. Mounier, N. M. J. Hall, S. Leroux, B. Sultan, and G. N. Kiladis, 2009: Dynamics of the West African monsoon. Part IV: Analysis of 25–90-day variability of convection and the role of the Indian monsoon. J. Climate, 22 , 1541–1565.

    • Search Google Scholar
    • Export Citation

  • Joseph, P. V., J. K. Eischeid, and P. J. Pyle, 1994: Interannual variability of the onset of the Indian summer monsoon and its association with atmospheric features, El Niño, and sea surface temperatures. J. Climate, 7 , 81–105.

    • Search Google Scholar
    • Export Citation

  • Joseph, P. V., K. P. Sooraj, and C. K. Rajan, 2006: The summer monsoon onset over process over south Asia and an objective method for the date of monsoon onset over Kerala. Int. J. Climatol., 26 , 1871–1893.

    • Search Google Scholar
    • Export Citation

  • Kanamitsu, M., W. Ebisuzaki, J. Woollen, S. K. Yang, J. J. Hnilo, M. Fiorion, and G. L. Potter, 2002: NCEP-DOE AMIP-II Reanalysis (R-2). Bull. Amer. Meteor. Soc., 83 , 1631–1643.

    • Search Google Scholar
    • Export Citation

  • Kinuthia, J. H., and G. C. Asnani, 1982: A newly found jet in north Kenya (Turkana channel). Mon. Wea. Rev., 110 , 1722–1728.

  • Knutson, T. R., and K. M. Weickmann, 1987: 30–60-day atmospheric oscillations: Composite life cycles of convection and circulation anomalies. Mon. Wea. Rev., 115 , 1407–1436.

    • Search Google Scholar
    • Export Citation

  • Koteswaram, P., 1958: The easterly jet stream in the tropics. Tellus, 10 , 42–57.

  • Krishnamurti, T. N., J. Molinari, and H. L. Pan, 1976: Numerical simulation of the Somali jet. J. Atmos. Sci., 33 , 2350–2362.

  • Krishnamurti, T. N., V. Wong, H. L. Pan, R. Pasch, J. Molinari, and P. Ardanuy, 1983: A three-dimensional planetary boundary layer model for the Somali jet. J. Atmos. Sci., 40 , 894–908.

    • Search Google Scholar
    • Export Citation

  • Lavender, S. L., and A. J. Matthews, 2009: Response of the West African monsoon to the Madden–Julian oscillation. J. Climate, 22 , 4097–4116.

    • Search Google Scholar
    • Export Citation

  • Lawrence, D. M., and P. J. Webster, 2002: The boreal summer intraseasonal oscillation: Relationship between northward and eastward movement of convection. J. Atmos. Sci., 59 , 1593–1606.

    • Search Google Scholar
    • Export Citation

  • Le Barbé, L., T. Lebel, and D. Tapsoba, 2002: Rainfall variability in West Africa during the years 1950–1990. J. Climate, 15 , 187–202.

    • Search Google Scholar
    • Export Citation

  • Li, C., and M. Yanai, 1996: The onset and interannual variability of the Asian summer monsoon in relation to land–sea thermal contrast. J. Climate, 9 , 358–375.

    • Search Google Scholar
    • Export Citation

  • LinHo, L. H., X. Huang, and N. Lau, 2008: Winter-to-spring transition in East Asia: A planetary-scale perspective of the South China spring rain onset. J. Climate, 21 , 3081–3096.

    • Search Google Scholar
    • Export Citation

  • Louvet, S., B. Fontaine, and P. Roucou, 2003: Active phases and pauses during the installation of the West African monsoon through 5-day CMAP rainfall data (1979–2001). Geophys. Res. Lett., 30 , 2271–2275.

    • Search Google Scholar
    • Export Citation

  • Lumb, F. E., 1966: Synoptic disturbances causing rainy period along the East African coast. Meteor. Mag., 95 , 150–159.

  • Maloney, E. D., and J. Shaman, 2008: Intraseasonal variability of the West African monsoon and Atlantic ITCZ. J. Climate, 21 , 2898–2918.

    • Search Google Scholar
    • Export Citation

  • Matthews, A. J., 2004: Intraseasonal variability over tropical Africa during northern summer. J. Climate, 17 , 2427–2440.

  • Murakami, T., 1987: Effects of the Tibetan Plateau. Monsoon Meteorology, C.-P. Chang and T. N. Krishnamurti, Eds., Oxford University Press, 235–270.

    • Search Google Scholar
    • Export Citation

  • Murakami, T., L-X. Chen, A. Xie, and M. L. Shresha, 1986: Eastward propagation of 30–60-day perturbations as revealed from outgoing longwave radiation data. J. Atmos. Sci., 43 , 961–971.

    • Search Google Scholar
    • Export Citation

  • Nicholson, S. E., 1996: A review of climate dynamics and climate variability in Eastern Africa. The Limnology, Climatology and Paleoclimatology of the East African Lakes, T. C. Johnson and E. O. Odada, Eds. Gordon and Breach, 25–56.

    • Search Google Scholar
    • Export Citation

  • Ogallo, L. J., 1985: Climatology of rainfall in East Africa. WMO Conf. on GATE, WAMEX and Tropical Meteorology, Dakar, Senegal, WMO, 96–102.

    • Search Google Scholar
    • Export Citation

  • Okoola, R. E., P. Camberlin, and J. M. Ininda, 2008: Wet periods along the East Africa coast and the extreme wet spell event of October 1997. J. Kenya Meteor. Soc., 2 , 67–83.

    • Search Google Scholar
    • Export Citation

  • Pai, D. S., and R. M. Nair, 2009: Summer monsoon onset over Kerala: New definition and prediction. J. Earth Syst. Sci., 118 , 123–135.

  • Pohl, B., S. Janicot, B. Fontaine, and R. Marteau, 2009: Implication of the Madden–Julian oscillation in the 40-day variability of the West African monsoon. J. Climate, 22 , 3769–3785.

    • Search Google Scholar
    • Export Citation

  • Raju, P. V. S., U. C. Mohanty, and R. Bhatla, 2005: Onset characteristics of the southwest monsoon over India. Int. J. Climatol., 25 , 167–182.

    • Search Google Scholar
    • Export Citation

  • Raju, P. V. S., U. C. Mohanty, and R. Bhatla, 2007: Interannual variability of onset of the summer monsoon over India and its prediction. Nat. Hazards, 42 , 287–300.

    • Search Google Scholar
    • Export Citation

  • Rao, V. B., J. P. Reyes Fernandez, and S. H. Franchito, 2000: Monsoonlike circulations in a zonally averaged numerical model with topography. Mon. Wea. Rev., 128 , 779–794.

    • Search Google Scholar
    • Export Citation

  • Riddle, E. E., and K. H. Cook, 2008: Abrupt rainfall transitions over the Greater Horn of Africa: Observations and regional model simulations. J. Geophys. Res., 113 , D15109. doi:10.1029/2007JD009202.

    • Search Google Scholar
    • Export Citation

  • Rodwell, M. J., 1997: Breaks in the Asian monsoon: The influence of Southern Hemisphere weather systems. J. Atmos. Sci., 54 , 2597–2611.

    • Search Google Scholar
    • Export Citation

  • Rodwell, M. J., and B. J. Hoskins, 1995: A model of the Asian summer monsoon. Part II: Cross-equatorial flow and PV behavior. J. Atmos. Sci., 52 , 1341–1356.

    • Search Google Scholar
    • Export Citation

  • Rodwell, M. J., and B. J. Hoskins, 1996: Monsoons and the dynamics of deserts. Quart. J. Roy. Meteor. Soc., 122 , 1385–1404.

  • Slingo, J., H. Spencer, B. Hoskins, P. Berrisford, and E. Black, 2004: The meteorology of the western Indian Ocean and the influence of the East African highlands. Philos. Trans. Roy. Soc. London, 363A , 25–42.

    • Search Google Scholar
    • Export Citation

  • Sultan, B., and S. Janicot, 2000: Abrupt shift of the ITCZ over West Africa and intra-seasonal variability. Geophys. Res. Lett., 27 , 3353–3356.

    • Search Google Scholar
    • Export Citation

  • Sultan, B., and S. Janicot, 2003: The West African monsoon dynamics. Part II: The “pre-onset” and the “onset” of the summer monsoon. J. Climate, 16 , 3407–3427.

    • Search Google Scholar
    • Export Citation

  • Uppala, S. M., and Coauthors, 2005: The ERA-40 Re-Analysis. Quart. J. Roy. Meteor. Soc., 131 , 2961–3012.

  • Wang, B., Q. Ding, and P. V. Joseph, 2009: Objective definition of the Indian summer monsoon onset. J. Climate, 22 , 3303–3316.

  • Webster, P. J., T. Palmer, M. Yanai, R. Tomas, V. Magana, J. Shukla, and A. Yasunari, 1998: Monsoons: Processes, predictability and the prospects for prediction. J. Geophys. Res., 103 , 14451–14510.

    • Search Google Scholar
    • Export Citation

  • Wheeler, M. C., and H. H. Hendon, 2004: An all-season real-time multivariate MJO index: Development of an index for monitoring and prediction. Mon. Wea. Rev., 132 , 1917–1932.

    • Search Google Scholar
    • Export Citation

  • Wu, M. L. C., S. Schubert, and N. E. Huang, 1999: The development of the South Asian summer monsoon and the intraseasonal oscillation. J. Climate, 12 , 2054–2075.

    • Search Google Scholar
    • Export Citation

  • Xavier, P. K., C. Marzin, and B. N. Goswami, 2007: An objective definition of the Indian summer monsoon season and a new perspective of the ENSO-monsoon relationship. Quart. J. Roy. Meteor. Soc., 133 , 749–764. doi:10.1002/qj.45.

    • Search Google Scholar
    • Export Citation

  • Xie, P., and P. A. Arkin, 1997: Global precipitation: A 17-year monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bull. Amer. Meteor. Soc., 78 , 2539–2558.

    • Search Google Scholar
    • Export Citation

  • Yin, M. T., 1949: A synoptic-aerologic study of the onset of the summer monsoon over India and Burma. J. Meteor., 6 , 393–400.

  • Yin, X., A. Gruber, and P. Arkin, 2004: Comparison of the GPCP and CMAP merged gauge–satellite monthly precipitation products for the period 1979–2001. J. Hydrometeor., 5 , 1207–1222.

    • Search Google Scholar
    • Export Citation

  • Zorita, E., and F. F. Tilya, 2002: Rainfall variability in northern Tanzania in the March–May season (long rains) and its links to large-scale climate forcing. Climate Res., 20 , 31–40.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 749 214 10
PDF Downloads 431 93 4