Tropical and Subtropical South American Intraseasonal Variability: A Normal-Mode Approach

Details

• Journal Title:
  Meteorology
• Personal Author:
  Teruya, André S. W. ; Mayta, Víctor C. ; Raphaldini, Breno ; Silva Dias, Pedro L. ; Sapucci, Camila R.
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research)
• Description:
  Instead of using the traditional space-time Fourier analysis of filtered specific atmospheric fields, a normal-mode decomposition method was used to analyze South American intraseasonal variability (ISV). Intraseasonal variability was examined separately in the 30–90-day band, 20–30-day band, and 10–20-day band. The most characteristic structure in the intraseasonal time-scale, in the three bands, was the dipole-like convection between the South Atlantic Convergence Zone (SACZ) and the central-east South America (CESA) region. In the 30–90-day band, the convective and circulation patterns were modulated by the large-scale Madden–Julian oscillation (MJO). In the 20–30-day and 10–20-day bands, the convection structures were primarily controlled by extratropical Rossby wave trains. The normal-mode decomposition of reanalysis data based on 30–90-day, 20–30-day, and 10–20-day ISV showed that the tropospheric circulation and CESA–SACZ convective structure observed over South America were dominated by rotational modes (i.e., Rossby waves, mixed Rossby-gravity waves). A considerable portion of the 30–90-day ISV was also associated with the inertio-gravity (IGW) modes (e.g., Kelvin waves), mainly prevailing during the austral rainy season. The proposed decomposition methodology demonstrated that a realistic circulation can be reproduced, giving a powerful tool for diagnosing and studying the dynamics of waves and the interactions between them in terms of their ability to provide causal accounts of the features seen in observations.
• Keywords:
  Environmental Engineering Industrial And Manufacturing Engineering Industrial And Manufacturing Engineering Industrial And Manufacturing Engineering
• Source:
  Meteorology, 3(2), 141-160
• DOI:
  https://doi.org/10.3390/meteorology3020007
• ISSN:
  2674-0494
• Format:
  PDF
• Publisher:
  MDPI AG
• Document Type:
  Journal Article
• Funding:
  Grant no. NA22OAR4310611
• License:
  https://creativecommons.org/licenses/by/4.0/
• Rights Information:
  CC BY
• Compliance:
  Library
• Main Document Checksum:
  urn:sha-512:89e91e0fd6dbbc77c01e6d851afb9e439ec38100a7af41316f1b6a66bcb6279a324795bd87fd8865a3ed5c5f4103f3986433f50ac872559479a66819b084bf70
• Download URL:
  https://repository.library.noaa.gov/view/noaa/64237/noaa_64237_DS1.pdf
• File Type:
  [PDF - 16.39 MB ]