Bosong Zhang

Geophysical Research Letters (2026)

The Influence of Tropopause Temperature Biases on Climate Model Simulations of Tropical Cyclones

Idealized profile perturbations demonstrate that upper-atmosphere temperature biases shift outflow temperature, alter PI, and strongly affect simulated TC frequency and ACE.

Potential Intensity Upper-Atmosphere Biases TC Frequency and ACE

~35%

Global TC frequency and ACE shifts in perturbation experiments

~80%

Change in hurricane frequency linked to upper-atmosphere thermal biases

PI Spread

Potential-intensity spread is strongly tied to 70-150 hPa thermal structure

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Paper Citation

Mahoney, A. D., B. J. Soden, B. Zhang, et al., 2026: The Influence of Tropopause Temperature Biases on Climate Model Simulations of Tropical Cyclones. Geophysical Research Letters. https://doi.org/10.1029/2025GL120545

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Scientific Logic

  • Question: How do upper-atmospheric temperature biases alter potential intensity and simulated tropical cyclone climatology?
  • Method: Idealized temperature-profile perturbation experiments diagnosing PI and TC-statistic responses to tropopause/lower-stratosphere bias adjustments.
  • Mechanism: Outflow temperature changes directly shift PI and thereby reshape frequency and intensity distributions of storms.
  • Main Findings: Realistic upper-atmosphere bias corrections produce large changes in TC frequency and ACE, with smaller but significant impacts on lifetime-intensity statistics.

Scientific Question

How much of the intermodel spread in tropical cyclone potential intensity and activity can be explained by biases in tropopause and lower-stratospheric temperatures under the same SST forcing?

Experimental Design

  • Cross-model analysis of CMIP6 and HighResMIP simulations.
  • Idealized HiRAM experiments with modified upper-atmospheric temperature profiles.
  • Diagnostics of potential intensity, TC frequency, ACE, and strong-storm statistics.

Key Findings

  • Intermodel PI spread is largely explained by differences in outflow temperature linked to upper-level thermal bias.
  • Correcting tropopause/lower-stratosphere bias produces large changes in TC frequency and accumulated cyclone energy.
  • Upper-atmosphere fidelity is a high-leverage constraint for credible TC-climate projections.

Figures from the Study

Extracted from Mahoney et al. (2026), https://doi.org/10.1029/2025GL120545.

Figure 1 (Extracted)

Extracted Figure 1 with outflow temperature correlations
Outflow-temperature relationships with tropical mean PI and 70-150 hPa mean temperature across model families and perturbation experiments.

Figure 2 (Extracted)

Extracted Figure 2 showing sounding biases
CMIP6/HighResMIP vertical temperature-profile bias structures and imposed HiRAM perturbations relative to reanalysis references.

Figure 3 (Extracted)

Extracted Figure 3 with TC metrics versus potential intensity
Sensitivity of mean annual TC frequency, ACE, strong-TC frequency, and lifetime maximum intensity to potential intensity changes.

Figure 4 (Extracted)

Extracted Figure 4 showing changes in strong tropical cyclone track density
Spatial changes in strong TC track density for m8K, m4K, p4K, and p8K relative to control.
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