Wellmeyer et al. (2026) Tropical Cyclone Intensity Sensitivity to Sea Surface Temperature and Mixed Layer Depth

Identification

• Journal: Atmospheric Research
• Year: 2026
• Date: 2026-01-03
• Authors: Evan David Wellmeyer, Antonio Ricchi, Rossella Ferretti
• DOI: 10.1016/j.atmosres.2025.108726

Research Groups

• Department of Physical and Chemical Sciences, University of L'Aquila, L'Aquila, Italy
• CETEMPS (Center of Excellence in Telesensing of Environment and Model Prediction of Severe Events), L'Aquila, Italy

Short Summary

This study systematically investigates how sea surface temperature (SST) and ocean mixed-layer depth (OMLD) modulate the rapid intensification (RI) and maximum intensity (MI) of Hurricanes Wilma and Rita (2005) using coupled atmosphere-ocean simulations. The findings reveal that SST is the dominant factor, significantly enhancing tropical cyclone intensity, energy transfer, and precipitation, while OMLD has a subtler but important modulating effect, particularly influencing storm trajectories.

Objective

• To systematically assess how variations in sea surface temperature (SST) and ocean mixed-layer depth (OMLD) influence the rapid intensification (RI), maximum intensity (MI), structural characteristics, and trajectories of two intense Atlantic tropical cyclones, Hurricanes Rita and Wilma (2005).

Study Configuration

• Spatial Scale: Two-way nested domain simulations with 9 km and 3 km resolutions, explicitly resolving inner-core structures (~20–50 km eyewall, ~3–5 km eyes). Total surface heat (TSH) calculated within a 330 km radius. Geographical focus on the Gulf of Mexico and Caribbean.
• Temporal Scale: Simulations cover the rapid intensification, maximum intensity, and weakening phases of the storms. Hurricane Rita: September 20, 12:00 UTC to September 25 UTC. Hurricane Wilma: October 18, 00:00 UTC to October 22, 00:00 UTC.

Methodology and Data

• Models used:
  • Weather Research and Forecasting (WRF) model/Advanced Research WRF (ARW) version 4.5.1 (atmospheric component).
  • Simplified 1D slab mixed-layer ocean model (oceanic component).
• Data sources:
  • GFS Final (FNL) global model (for WRF initialization and boundary conditions).
  • European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 Reanalysis (for SST anomaly calculation, 1985–2005 reference period).
  • Nation Oceanographic and Atmospheric Administration (NOAA) and National Hurricane Centers (NHC) Atlantic hurricane database “HURDAT2” dataset (observational data for TC parameters).
  • Integrated Multi-satellitE Retrievals for GPM Final (IMERG) (for simulated precipitation validation).

Main Results

• Sea surface temperature (SST) is the dominant control on tropical cyclone (TC) intensity, with minimum central sea level pressure (CSLP) sensitivity ranging from approximately 16.5 hPa °C⁻¹ for Rita to 19.6 hPa °C⁻¹ for Wilma.
• Warmer SSTs lead to significantly higher deepening rates (Rita: 0.375 hPa h⁻¹ °C⁻¹, Wilma: 0.54 hPa h⁻¹ °C⁻¹), increased energy transfer from the ocean, elevated near-surface equivalent potential temperature (Rita: 7.21 K °C⁻¹, Wilma: 9.03 K °C⁻¹), more symmetrical wind fields, and higher accumulated cyclone energy (ACE).
• Deeper ocean mixed-layer depth (OMLD) enhances thermodynamic support but its effectiveness is constrained by SST conditions and storm trajectory, limiting total surface heat flux in the storm's vicinity. OMLD effects are subtler, with CSLP sensitivities of 0.38 hPa m⁻¹ for Rita and 0.14 hPa m⁻¹ for Wilma.
• Remote heat fluxes across a broader region, not just beneath the storm core, play a crucial role in determining maximum intensity and deepening.
• Warmer SST scenarios (+3 °C) resulted in substantial westward landfall shifts, up to approximately 300 km, emphasizing the potential of ocean heat in altering trajectories.
• Increased SST enhanced precipitation intensity and spatial coverage, with peak precipitation rising by approximately 61% for Rita and 70% for Wilma in the warmest scenarios (+3 °C). OMLD modulation altered peak rainfall by -13% to +50%, showing stronger sensitivity in Rita.
• Control simulations generally underestimated observed peak intensity and deepening rates for both hurricanes.

Contributions

• Provides a systematic and quantitative analysis of the combined impacts of SST and OMLD variations on the rapid intensification, maximum intensity, structural characteristics, and trajectories of two exceptionally intense Atlantic TCs (Hurricanes Rita and Wilma).
• Quantifies the distinct and robust energetic sensitivities of TCs to SST (e.g., ~15-20 hPa °C⁻¹ for CSLP) and the more subtle yet meaningful sensitivities to OMLD.
• Highlights the critical role of remote heat fluxes, extending beyond the immediate storm core, in determining maximum intensity and deepening.
• Demonstrates the potential for significant TC trajectory shifts (up to 300 km) due to changes in ocean heat content, particularly under warmer SST scenarios.
• Emphasizes the imperative for accurate representation of upper-ocean thermal structures in operational TC forecasting to improve predictions of intensity and trajectories, especially in the context of projected climate change.
• Utilizes a simplified 1D ocean model to isolate the individual impacts of OMLD, offering valuable guidance for the design and interpretation of high-resolution modeling applications and future climate-change scenarios.

Funding

• National Centre for HPC, Big Data and Quantum Computing - PNRR Project, funded by the European Union - Next Generation EU.
• Special Project “Exploiting Coupled, High-resolution modelling to simulate severe mediterranean cyclOgenES (ECHOES)“ funded by ECMWF.

Citation

@article{Wellmeyer2026Tropical,
  author = {Wellmeyer, Evan David and Ricchi, Antonio and Ferretti, Rossella},
  title = {Tropical Cyclone Intensity Sensitivity to Sea Surface Temperature and Mixed Layer Depth},
  journal = {Atmospheric Research},
  year = {2026},
  doi = {10.1016/j.atmosres.2025.108726},
  url = {https://doi.org/10.1016/j.atmosres.2025.108726}
}