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The evaluation of the North Atlantic climate system in UKESM1 historical simulations for CMIP6

Robson, J., Aksenov, Y., Bracegirdle, T. J., Dimdore-Miles, O., Griffiths, P. T., Grosvenor, D. P., Hodson, D. L.R., Keeble, J., MacIntosh, C., Megann, A., Osprey, S., Povey, A. C., Schröder, D., Yang, M., Archibald, A. T., Carslaw, K. S., Gray, L., Jones, C., Kerridge, B., Knappett, D. , Kuhlbrodt, T. ORCID: https://orcid.org/0000-0003-2328-6729, Russo, M., Sellar, A., Siddans, R., Sinha, B., Sutton, R., Walton, J. and Wilcox, L. J. (2020) The evaluation of the North Atlantic climate system in UKESM1 historical simulations for CMIP6. Journal of Advances in Modeling Earth Systems, 12 (9). e2020MS002126. ISSN 1942-2466

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To link to this item DOI: 10.1029/2020MS002126

Abstract/Summary

Earth System models enable a broad range of climate interactions that physical climate models are unable to simulate. However, the extent to which adding Earth System components changes or improves the simulation of the physical climate is not well understood. Here we present a broad multi-variate evaluation of the North Atlantic climate system in historical simulations of the UK Earth System Model (UKESM1) performed for CMIP6. In particular, we focus on the mean state and the decadal timescale evolution of important variables that span the North Atlantic Climate system. In general, UKESM1 performs well and realistically simulates many aspects of the North Atlantic climate system. Like the physical version of the model, we find that changes in external forcing, and particularly aerosol forcing, are an important driver of multi-decadal change in UKESM1, especially for Atlantic Multi-decadal Variability and the Atlantic Meridional Overturning Circulation. However, many of the shortcomings identified are similar to common biases found in physical climate models, including the physical climate model that underpins UKESM1. For example, the summer jet is too weak and too far poleward; decadal variability in the winter jet is underestimated; intra-seasonal stratospheric polar vortex variability is poorly represented; and Arctic sea ice is too thick. Forced shortwave changes may be also too strong in UKESM1, which, given the important role of historical aerosol forcing in shaping the evolution of the North Atlantic in UKESM1, motivates further investigation. Therefore, physical model development, alongside Earth System development, remains crucial in order to improve climate simulations.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical, Physical and Computational Sciences > National Centre for Earth Observation (NCEO)
Faculty of Science > School of Mathematical, Physical and Computational Sciences > NCAS
Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:92263
Uncontrolled Keywords:North Atlantic, Earth System Model, CMIP6, model evaluation
Publisher:American Geophysical Union

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