• Aceituno, P., 1988: On the functioning of the Southern Oscillation in the South American sector. Part I: Surface climate. Mon. Wea. Rev., 116 , 505524.

    • Search Google Scholar
    • Export Citation
  • Barros, V., , M. González, , B. Liebmann, , and I. Camilloni, 2000: Influence of the South Atlantic convergence zone and South Atlantic sea surface temperature on interannual summer rainfall variability in southeastern South America. Theor. Appl. Climatol., 67 , 123133.

    • Search Google Scholar
    • Export Citation
  • Cazes-Boezio, G., , A. W. Robertson, , and C. R. Mechoso, 2003: Seasonal dependence of ENSO teleconnections over South America and relationships with precipitation in Uruguay. J. Climate, 16 , 11591176.

    • Search Google Scholar
    • Export Citation
  • Enfield, D. B., , and A. M. Mestas-Nuñez, 1999: Multiscale variabilities in global sea surface temperatures and their relationships with tropospheric climate patterns. J. Climate, 12 , 27192733.

    • Search Google Scholar
    • Export Citation
  • Grimm, A. M., 2003: The El Niño impact on the summer monsoon in Brazil: Regional processes versus remote influences. J. Climate, 16 , 263280.

    • Search Google Scholar
    • Export Citation
  • Grimm, A. M., 2004: How do La Niña events disturb the summer monsoon system in Brazil? Climate Dyn., 22 , 123138.

  • Grimm, A. M., , and P. L. Silva Dias, 1995: Analysis of tropical–extratropical interactions with influence functions of a barotropic model. J. Atmos. Sci., 52 , 35383555.

    • Search Google Scholar
    • Export Citation
  • Grimm, A. M., , V. R. Barros, , and M. E. Doyle, 2000: Climate variability in southern South America associated with El Niño and La Niña events. J. Climate, 13 , 3558.

    • Search Google Scholar
    • Export Citation
  • Grimm, A. M., , C. S. Vera, , and C. R. Mechoso, 2005: The South American monsoon system. The Global Monsoon System: Research and Forecast, WMO/TD1266-TMRP 70, C.-P. Chang, B. Wang, and N.-C. G. Lau, Eds., WMO, 219–238. [Available online at http://www.wmo.int/pages/prog/arep/tmrp/documents/global_monsoon_system_IWM3.pdf.].

    • Search Google Scholar
    • Export Citation
  • Grimm, A. M., , J. Pal, , and F. Giorgi, 2007: Connection between spring conditions and peak summer monsoon rainfall in South America: Role of soil moisture, surface temperature, and topography in eastern Brazil. J. Climate, 20 , 59295945.

    • Search Google Scholar
    • Export Citation
  • Higgins, W., , and W. Shi, 2000: Dominant factors responsible for interannual variability of the summer monsoon in the southwestern United States. J. Climate, 13 , 759776.

    • Search Google Scholar
    • Export Citation
  • Higgins, W., , K. C. Mo, , and Y. Yao, 1998: Interannual variability of the U.S. summer precipitation regime with emphasis on the southwestern monsoon. J. Climate, 11 , 25822606.

    • Search Google Scholar
    • Export Citation
  • Hu, Q., , and S. Feng, 2002: Interannual rainfall variations in the North American summer monsoon region: 1900-98. J. Climate, 15 , 11891202.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77 , 437471.

  • Liebmann, B., , G. N. Kiladis, , C. S. Vera, , A. C. Saulo, , and L. M. V. Carvalho, 2004: Subseasonal variations of rainfall in South America in the vicinity of the low-level jet east of the Andes and comparison to those in the South Atlantic convergence zone. J. Climate, 17 , 38293842.

    • Search Google Scholar
    • Export Citation
  • Paegle, J. N., , and K. C. Mo, 2002: Linkages between summer rainfall variability over South America and sea surface temperature anomalies. J. Climate, 15 , 13891407.

    • Search Google Scholar
    • Export Citation
  • Paegle, J. N., , L. A. Byerle, , and K. C. Mo, 2000: Intraseasonal modulation of South American summer precipitation. Mon. Wea. Rev., 128 , 837850.

    • Search Google Scholar
    • Export Citation
  • Paegle, J. N., and Coauthors, 2002: Progress in pan American CLIVAR research: Understanding the South American monsoon. Meteorologica, 27 , 130.

    • Search Google Scholar
    • Export Citation
  • Rayner, N. A., , D. E. Parker, , E. B. Horton, , C. K. Folland, , L. V. Alexander, , D. P. Rowell, , E. C. Kent, , and A. Kaplan, 2003: Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res., 108 , 4407. doi:10.1029/2002JD002670.

    • Search Google Scholar
    • Export Citation
  • Robertson, A. W., , and C. R. Mechoso, 2000: Interannual and interdecadal variability of the South Atlantic convergence zone. Mon. Wea. Rev., 128 , 29472957.

    • Search Google Scholar
    • Export Citation
  • Ropelewski, C. F., , and M. S. Halpert, 1987: Global and regional scale precipitation patterns associated with the El Niño/Southern Oscillation. Mon. Wea. Rev., 115 , 16061626.

    • Search Google Scholar
    • Export Citation
  • Rossato, L., , R. C. S. Alvalá, , and J. Tomasella, 2004: Spatiotemporal variation of soil moisture in Brazil: Analysis of the mean conditions in the period 1971–1990 (in Portuguese). Rev. Bras. Meteor., 19 , 113122.

    • Search Google Scholar
    • Export Citation
  • Zhou, J., , and W. K-M. Lau, 2001: Principal modes of interannual and decadal variability of summer rainfall over South America. Int. J. Climatol., 21 , 16231644.

    • Search Google Scholar
    • Export Citation
  • Zhu, C., , D. P. Lettenmaier, , and T. Cavazos, 2005: Role of antecedent land surface conditions on North American monsoon rainfall variability. J. Climate, 18 , 31043121.

    • Search Google Scholar
    • Export Citation
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Interannual Variability and Seasonal Evolution of Summer Monsoon Rainfall in South America

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  • 1 Department of Physics, and Post Graduate Program on Water Resources and Environmental Engineering, Federal University of Paraná, Curitiba, Brazil
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Abstract

The analysis of the interannual variability of the South American monsoon rainfall is carried out separately for austral spring and summer (and for November and January), based on a 40-yr station gauge dataset. Relationships between modes of variability in these seasons show the influence of antecedent conditions in spring (or November) on the evolution of the monsoon rainfall in peak summer (or January). In spring the first mode is dipolelike, with opposite loadings over central-eastern and southeastern South America. It is connected with ENSO. The second mode shows the highest loadings slightly south of the South Atlantic convergence zone. The leading mode of summer also features dipolelike oscillations between central-eastern and southeastern South America, but is not strongly connected with ENSO. The second mode represents the impact of ENSO, and the third is modulated by SST anomalies in the southern tropical Atlantic.

Significant relationships are disclosed between the first dipolelike modes of spring and summer rainfall and thus between the rainfall in spring and summer over central-eastern South America, which includes part of the monsoon core region. These dipolelike modes are associated with a rotational anomaly over southeast Brazil that either conveys moisture flux into central-eastern Brazil (if it is cyclonic) or into southeastern South America (if it is anticyclonic). In spring this anomaly seems to be remotely forced, but after strong rainfall anomalies over central-eastern Brazil in spring, it tends to reverse sign in peak summer, inverting the dipolelike rainfall anomalies. This reversal is hypothesized to be locally forced by surface–atmosphere feedback triggered by the spring anomalies, as weaker teleconnections in summer allow local processes that are stronger in summer to overcome remote forcing. SST and circulation anomalies associated with the first modes in spring and summer, and also the relationship between the first summer mode and surface temperature in spring, are consistent with that hypothesis.

Corresponding author address: Dr. Alice M. Grimm, Dept. of Physics, Federal University of Paraná, Caixa Postal 19044, 81531-990 Curitiba, PR, Brazil. Email: grimm@fisica.ufpr.br

Abstract

The analysis of the interannual variability of the South American monsoon rainfall is carried out separately for austral spring and summer (and for November and January), based on a 40-yr station gauge dataset. Relationships between modes of variability in these seasons show the influence of antecedent conditions in spring (or November) on the evolution of the monsoon rainfall in peak summer (or January). In spring the first mode is dipolelike, with opposite loadings over central-eastern and southeastern South America. It is connected with ENSO. The second mode shows the highest loadings slightly south of the South Atlantic convergence zone. The leading mode of summer also features dipolelike oscillations between central-eastern and southeastern South America, but is not strongly connected with ENSO. The second mode represents the impact of ENSO, and the third is modulated by SST anomalies in the southern tropical Atlantic.

Significant relationships are disclosed between the first dipolelike modes of spring and summer rainfall and thus between the rainfall in spring and summer over central-eastern South America, which includes part of the monsoon core region. These dipolelike modes are associated with a rotational anomaly over southeast Brazil that either conveys moisture flux into central-eastern Brazil (if it is cyclonic) or into southeastern South America (if it is anticyclonic). In spring this anomaly seems to be remotely forced, but after strong rainfall anomalies over central-eastern Brazil in spring, it tends to reverse sign in peak summer, inverting the dipolelike rainfall anomalies. This reversal is hypothesized to be locally forced by surface–atmosphere feedback triggered by the spring anomalies, as weaker teleconnections in summer allow local processes that are stronger in summer to overcome remote forcing. SST and circulation anomalies associated with the first modes in spring and summer, and also the relationship between the first summer mode and surface temperature in spring, are consistent with that hypothesis.

Corresponding author address: Dr. Alice M. Grimm, Dept. of Physics, Federal University of Paraná, Caixa Postal 19044, 81531-990 Curitiba, PR, Brazil. Email: grimm@fisica.ufpr.br

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