Convectively Coupled Kelvin Waves over Tropical South America

Details

• Journal Title:
  Journal of Climate
• Personal Author:
  Mayta, Victor C. ; Kiladis, George N. ; Dias, Juliana ; Silva Dias, Pedro L. ; Gehne, Maria
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research) ; ESRL (Earth System Research Laboratory) ; CIRES (Cooperative Institute for Research in Environmental Sciences)
• Description:
  Rainfall over tropical South America is known to be modulated by convectively coupled Kelvin waves (CCKWs). In this work, the origin and dynamical features of South American Kelvin waves are revisited using satellite-observed brightness temperature, radiosonde, and reanalysis datasets. Two main types of CCKWs over the Amazon are considered: Kelvin waves with a Pacific precursor, and Kelvin waves with a precursor originating over South America. Amazonian CCKWs associated with a preexisting Kelvin convection in the eastern Pacific account for about 35% of the total events. The cases with South American precursors are associated with either pressure surges in the western Amazon from extratropical wave train activity, responsible for 40% of the total events, or “in situ” convection that locally excites CCKWs, accounting for the remaining 25%. The analysis also suggests that CCKWs associated with different precursors are sensitive to Pacific sea surface temperature. Kelvin wave events with a Pacific precursor are more common during ENSO warm events, while Kelvin waves with extratropical South American precursors show stronger activity during La Niña events. This study also explores other triggering mechanisms of CCKWs over the Amazon. These mechanisms are associated with 1) extratropical Rossby wave trains not necessarily of extratropical South American origin; 2) CCKWs initiated in response to the presence of the southern and/or double intertropical convergence zone (ITCZ) in the eastern Pacific Ocean; and 3) possible interaction between CCKWs and other equatorial waves in the Amazon.
• Keywords:
  Atmospheric circulation Kelvin waves
• Source:
  Journal of Climate, 34(16), 6531-6547
• DOI:
  https://doi.org/10.1175/JCLI-D-20-0662.1
• Document Type:
  Journal Article
• Rights Information:
  Other
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha256:270f1bd811d8025a8e19597caef8104033c6316f3d504808d208110160a3c097
• Download URL:
  https://repository.library.noaa.gov/view/noaa/44554/noaa_44554_DS1.pdf
• File Type:
  [PDF - 5.44 MB ]