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MJO impacts on South America and their modulation by ENSO in MetUM-GOML3 model
  • Laís Gonçalves Fernandes,
  • Alice Marlene Grimm,
  • Nicholas Pappas Klingaman
Laís Gonçalves Fernandes
Portland State University

Corresponding Author:[email protected]

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Alice Marlene Grimm
Federal University of Paraná
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Nicholas Pappas Klingaman
University of Reading
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The impacts of the Madden-Julian Oscillation (MJO) on the South American monsoon season (December-February) and possible changes during El Niño (EN) and La Niña (LN) events are analyzed in the UK Met Office Unified Model Global Ocean Mixed Layer configuration (MetUM-GOML3). Experiments sixty years long, with and without El Niño-Southern Oscillation (ENSO), considering different spatial resolutions, are performed to assess if ENSO influences several MJO characteristics, including the teleconnections to South America (SA). Simulations without ENSO show: (i) an extratropical teleconnection triggered by enhanced convection in the central-east subtropical South Pacific (CSSP) and its strongest impact on central-east South American precipitation in phase 8, earlier than in observations (phase 1). (ii) An extratropical teleconnection, triggered by suppressed convection over the same region, with strongest impact on South American precipitation in phase 4, with opposite sign. (iii) Increased resolution enhances the MJO convection and the South American circulation-precipitation dipole. ENSO affects the basic state and the MJO convection, which modulate teleconnections to SA in simulations with ENSO cycles. EN (LN) strengthens (deteriorates) MJO propagation and its convection. However, both EN and LN produce enhanced convection over the CSSP in phase 8. The extratropical teleconnections and their impacts are stronger under ENSO with respect to those in simulations without ENSO. Hence, both simulated ENSO states generate forcing that more efficiently triggers teleconnections than simulations without ENSO, indicating nonlinear ENSO effects on MJO anomalies over SA.
21 Mar 2024Submitted to ESS Open Archive
25 Mar 2024Published in ESS Open Archive