Regional ocean grid refinement and its effect on simulated atmospheric climate

Williams, J. ORCID: https://orcid.org/0000-0002-0680-0098, Behrens, E., Morgenstern, O., Hayek, W., Teixeira, J. and Varma, V. (2023) Regional ocean grid refinement and its effect on simulated atmospheric climate. Weather & Climate, 43. pp. 16-31.

Abstract/Summary

In this work we analyse the impact of including a regional, high-resolution ocean model on simulatedatmospheric climate in a coupled earth system model. The resolution of the regional, nested oceanmodel is approximately 0.2° compared to the ~1° resolution of the global ocean model within which itis embedded and this work complements previously published work on ocean circulation and marineheatwaves using this setup, referred to as the New Zealand Earth System Model, NZESM. After a briefdiscussion of the wider model setup, the persistent Southern Ocean warm bias in climate models andthe validation data sets used, we show the effects of the altered ocean physics on air temperature,precipitation and evaporation, latent and sensible surface heat balances, westerly winds, the storm trackand the effect on total cloud amount. Overall we find that the NZESM provides a better representation ofregional atmospheric climate compared to its parent model – UKESM1 – although this improvement is notuniversal. For example, although the NZESM shows better agreement in surface air temperature withinthe nested ocean region, there is also some deterioration in the agreement at higher southern latitudeswhere the seasonal sea ice edge coincides with a transition from negative to positive correlation betweenair temperature and cloud amount. The lack of additional model tuning in the NZESM after the nestedocean model’s inclusion largely accounts for the presence of these improvement-deterioration pairs withrespect to observations. The reader is encouraged to read the paper of Behrens et al. (Behrens et al, 2020) before this one since it provides much additional information which will aid understanding. This study aims to provide a high-level reference ontology for how changing one aspect of the ocean physics in acoupled model can impact simulated atmospheric climate.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/124970
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Meteorological Society of New Zealand
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