Diagrams from the paper.
The El Niño composites in the control low-resolution simulation (left panels), the simulation with tropical cyclones winds from a high-resolution simulation imposed in the low-resolution simulation (middle panels), and their difference (right panels). The colors in the panels represent Hövmoller composites in the equatorial Pacific (2S - 2N), with time in the y-axis running from bottom (January year 0) to top (May year +2). The top panels represent the thermocline feedback term and the bottom panels the zonal advection feedback term as defined in the sea surface temperature (SST) tendency term. The units are given oC/month. The contours on the right panels are a measure of the integrated near-tropical tropical cyclone wind power scaled by 2.1x10-8. Credit: Li et al. [2023], Figure 4
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Source: Geophysical Research Letters

In a new study, Li et al. [2023] examine the hypothesis that tropical cyclones can influence the characteristics of El Niño–Southern Oscillations (ENSO) using a suite of simulations of the CESM1.3 Earth System model with different resolutions. The tropical cyclone surface winds are extracted from a high-resolution model simulation and used to force a low-resolution simulation. Additionally, a control low-resolution simulation (not forced with tropical cyclone surface winds) and an additional high-resolution eddy-resolving ocean simulation are considered.

The results show that in this model, tropical cyclones can modulate the frequency, magnitude, and timing of the El Niño events, such that these characteristics become closer to observed ones. In particular, tropical cyclones lead to more frequent El Niño events in this model and the magnitude of El Niño events is only affected in the case of strong events. These results suggest that tropical cyclones are essential ingredients of ENSO dynamics.

Citation: Li, H., Hu, A., & Meehl, G. A. (2023). Role of tropical cyclones in determining ENSO characteristics. Geophysical Research Letters, 50, e2022GL101814. https://doi.org/10.1029/2022GL101814

—Suzana Camargo, Editor, Geophysical Research Letters

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