Toward Eliminating the Decades‐Old “Too Zonal and Too Equatorward” Storm‐Track Bias in Climate Models

• Published in: Journal of advances in modeling earth systems 2023-02, Vol.15 (2), p.e2022MS003482-n/a
• Main Author: Schemm, Sebastian
• Format: Article
• Language: English
• Subjects: Abrupt/Rapid Climate Change; Air/Sea Constituent Fluxes; Air/Sea Interactions; Atmospheric; Atmospheric Composition and Structure; Atmospheric Effects; Atmospheric Processes; Avalanches; Benefit‐cost Analysis; Bias; Biogeosciences; Climate and Interannual Variability; Climate Change and Variability; Climate Dynamics; Climate Impact; Climate Impacts; Climate models; Climate prediction; Climate Variability; Climatology; Computational Geophysics; Cryosphere; Cyclone tracks; Cyclones; Decadal Ocean Variability; Disaster Risk Analysis and Assessment; Earth System Modeling; Earthquake Ground Motions and Engineering Seismology; Effusive Volcanism; Equator; Explosive Volcanism; Future climates; General Circulation; Geodesy and Gravity; Geological; Global Change; Global Change from Geodesy; Global Climate Models; Gravity and Isostasy; Hydrological Cycles and Budgets; Hydrology; Idealized Model; Impacts of Global Change; Informatics; kilometer‐scale resolution; Land/Atmosphere Interactions; Marine Geology and Geophysics; Mass Balance; Mesoscale Meteorology; Modeling; Modelling; Mud Volcanism; Natural Hazards; Nests; Numerical Modeling; Numerical Solutions; Ocean circulation; Ocean currents; Ocean influence of Earth rotation; Ocean Monitoring with Geodetic Techniques; Ocean/Atmosphere Interactions; Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions; Oceanic; Oceanography: General; Oceanography: Physical; Oceans; Paleoceanography; Physical Modeling; Policy Sciences; Precipitation; Radio Oceanography; Radio Science; Regional Climate Change; Regional Modeling; Risk; Sea Level Change; Sea Level: Variations and Mean; Sea surface; Sea surface temperature; Seismology; Simulation; Solid Earth; Storm tracks; Storms; Surface temperature; Surface Waves and Tides; Theoretical Modeling; Tracking; Tsunamis and Storm Surges; Volcanic Effects; Volcanic Hazards and Risks; Volcano Monitoring; Volcano Seismology; Volcano/Climate Interactions; Volcanology; Water Cycles
• ISSN: 1942-2466; 1942-2466
• DOI: 10.1029/2022MS003482

Generations of climate models exhibit biases in their representation of North Atlantic storm tracks, which tend to be too far near the equator and too zonal. Additionally, models have difficulties simulating explosive cyclone growth. These biases are one of the reasons for the uncertainties in projections of future climate over Europe, and the underlying causes have yet to be determined. All three biases are shown to be related, and diabatic processes are pointed to as a likely cause. To demonstrate this, two hemispherically symmetric storm tracks forming downstream of an idealized sea surface temperature (SST) front on an aquaplanet are examined using the seamless weather and climate prediction model ICOsahedral Non‐hydrostatic and its grid refinement capabilities. The analyzed perpetual boreal winter has a global grid spacing of 20 km, two bi‐directionally interacting grid nests over the Northern Hemisphere that refine the grid to 10‐km spacing over much of the stormtrack and further to 5‐km spacing near the SST front. In contrast, no grid refinement is performed for the Southern Hemisphere. Feature‐based cyclone tracking shows that the poleward propagation in the NH is enhanced, so the high‐resolution storm track is less equatorward and less zonal; explosive deepening rates are more frequent and precipitation rates are amplified. The implication is that resolving diabatic processes on the storm scale improves all three intersecting biases in the representation of storm tracks. While new challenges arise at cloud resolving scales, much improvement for the representation of storm tracks will be gained once climate models resolve the meso‐γ scale. Plain Language Summary Most people in the mid‐latitudes will experience climate change through changes in their daily weather. Much of the daily weather variability is determined by the propagation of extratropical low pressure systems. The direction of propagation of these systems dictates regional precipitation patterns, and an accurate representation of the track is important to reduce uncertainties in future projections. However, climate models simulate tracks that are too zonal (i.e., east–west), too close to the equator and too weak. Using an idealized simulation, this study shows that individual tracks will propagate more poleward, intensification rates will increase and the tracks become less zonal at storm‐resolving model resolution, helping to reduce this well‐known circulation bias in climate models. K