How well CMIP6 captures North American storm pulses
An Eulerian three-parameter storm metric shows CMIP6 GCMs share cyclone biases versus ERA5, while 12 km CRCM6 is usually closest.
Source
An Eulerian evaluation of intense low-pressure systems over North America in CMIP6 and a regional climate model
Study at a glance
- Design
- Computational / modelling — Eulerian intense-cyclone metrics comparing ERA5, 27 CMIP6 GCMs, and CRCM6
- N
- N=27 · 27 CMIP6 simulations plus 5 CRCM6-GEM5 runs evaluated against ERA5 (1980–2014)
- Population
- Intense low-pressure systems over North America in reanalysis and climate models
- Outcome
- Biases in cyclone depth/tendency and skill of 12 km CRCM6 vs GCMs
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How well CMIP6 captures North American storm pulses
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Evaluation uses 27 CMIP6 simulations and 5 CRCM6-GEM5 regional simulations.
ERA5 reanalysis, the 27 CMIP6 model simulations and the 5 CRCM6-GEM5 regional model simulations.
CRCM6-GEM5 at 12-km resolution generally exhibits the smallest errors.
Simulations using the CRCM6-GEM5 model at 12-km resolution generally exhibit the smallest errors across the entire domain.
What they did
Authors identified the strongest yearly sea-level-pressure anomalies at each North American grid point in ERA5, 27 CMIP6 models, and CRCM6-GEM5 (1980–2014), then fit 3-day pressure and humidity traces with peak, tendency, and asymmetry.
What they found
GCMs underestimate oceanic cyclone depth and overestimate it over land. Resolution helps most over stormy oceans. 12 km CRCM6 has the smallest domain errors even when driven by different CMIP6 models, so the regional model—not the driver—sets much of the skill.
The limits
What it doesn't show
“Errors” are differences from imperfect ERA5, not truth; the linear 3-day fit is poor for tropical cyclones; there is no Lagrangian track or future-scenario analysis.
Key terms
- Eulerian storm metric
- Diagnosing cyclones from local time series rather than tracking storm objects.
- Peak
- Pressure or humidity at the time of the strongest pressure anomaly.
- Tendency
- Mean rate of change over the 36 h before and after the peak.
- Asymmetry
- Imbalance between deepening and filling phases of the pulse.
- CRCM6-GEM5
- 12 km Canadian regional climate model nested in reanalysis or CMIP6.
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Observational benchmark:
Common questions
What is the observational reference?
ERA5, 1980–2014.
How many GCMs?
27 CMIP6 models plus CRCM6 simulations.
Which configuration is generally best?
12 km CRCM6-GEM5.
Does the CMIP6 driver dominate RCM errors?
No—CRCM6 skill is similar across drivers.
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