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Drivers of biases in the CMIP6 extratropical storm tracks. Part 1: Northern Hemisphere

Priestley, M. D. K., Ackerley, D., Catto, J. L., Hodges, K. and McDonald, R. (2022) Drivers of biases in the CMIP6 extratropical storm tracks. Part 1: Northern Hemisphere. Journal of Climate. ISSN 1520-0442 (In Press)

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The ability of climate models to represent extratropical storm tracks is vital to provide useful projections. This representation in the Northern Hemisphere has improved from the 5th to 6th coupled model intercomparison project. Here we investigate the remaining and persistent biases in the CMIP6 models, by making use of atmosphere only simulations and other diagnostic tools. The AMIP6 simulations reveal that biases in sea surface temperatures (SSTs) across the North Pacific in winter modify the atmospheric temperature gradient, which is associated with an equatorward bias of the storm track. In the North Atlantic, cyclones do not propagate poleward enough, which is partly driven by cold SSTs to the south of Greenland decreasing latent heat fluxes. In summer, excessive heating across central Asia and the Tibetan Plateau leads to modifications to baroclinicity in the region, resulting in reduced rates of cyclogenesis across eastern China, and a persistent negative bias in storm track density in CMIP6 over eastern Asia and the North Pacific. The AMIP6 models still retain biases relative to ERA5 and therefore improvements in modelling the atmosphere and land surface interactions are still required, however many of the NH biases are related in some way to the distribution of SSTs and large reductions in mean state biases could be made through improved ocean modelling.

Item Type:Article
Divisions:Science > School of Mathematical, Physical and Computational Sciences > NCAS
Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:99466
Publisher:American Meteorological Society

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