Meteorology and Atmospheric Physics

, Volume 93, Issue 1–2, pp 17–35 | Cite as

Observational study of the seasonality of the submonthly and intraseasonal signal over the tropics

  • M. I. Vitorino
  • P. L. da Silva Dias
  • N. J. Ferreira
Article

Summary

Atmospheric variability in outgoing long-wave radiation (OLR) and tropospheric relative vorticity (VOR) over the South American region was studied from 1979 to 1996 using the complex Morlet wavelet function. The analyses focus on spatial variation in intraseasonal and submonthly scales. Scalograms were used to measure submonthly intraseasonal oscillations in convection, which were found to be predominant in the tropical regions. However, 7-day and 15-day oscillations were observed at tropical and extratropical latitudes in spring and winter, indicating that transient disturbances play a more prominent role. Regarding VOR, tropical energy intensities were highest in the spring and summer, whereas subtropical and extratropical energy intensities were highest in the autumn and winter. The dynamics of the 25-day and 45-day VOR oscillations indicates a possible correlation with Rossby waves over the eastern tropical Pacific Ocean, mainly during the summer. During winter, the 7-day and 15-day VOR oscillations are more frequent at higher latitudes and are enhanced along storm tracks. It was also observed that convection amplitudes in the regions of maximum intensity change appreciably from year to year and from season to season, showing that the behavior of the submonthly and intraseasonal oscillations is nonperiodic and correlates strongly with El Niño/Southern Oscillation years. These results confirm the efficiency of wavelet analysis for time-scale studies of atmospheric variability.

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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • M. I. Vitorino
    • 1
  • P. L. da Silva Dias
    • 1
  • N. J. Ferreira
    • 2
  1. 1.Departamento de Ciências AtmosféricasInstituto de Astronomia, Geofísica e Ciências Atmosféricas da Universidade de São PauloBrazil
  2. 2.Laboratório de Meteorologia e Oceanografia, Instituto Nacional de Pesquisas EspaciaisSão Jose dos CamposBrazil

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