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Regional ocean grid refinement and its effect on simulated atmospheric climate
  • +3
  • Jonny Williams,
  • Erik Behrens,
  • Olaf Morgenstern,
  • João Teixeira,
  • Vidya Varma,
  • Wolfgang Hayek
Jonny Williams
National Institute of Water and Atmospheric Research (NIWA)

Corresponding Author:jonny.williams@niwa.co.nz

Author Profile
Erik Behrens
National Institute of Water and Atmospheric Research (NIWA)
Olaf Morgenstern
National Institute of Water and Atmospheric Research (NIWA)
João Teixeira
Met Office
Vidya Varma
Now at Institut für Geophysik und Meteorologie, Universität zu Köln, National Institute of Water and Atmospheric Research (NIWA)
Wolfgang Hayek
National Institute of Water and Atmospheric Research (NIWA)


In this work we show the effect on atmospheric climate of including a two-way-nested, high-resolution ocean model in the region surrounding New Zealand within a coupled earth system model. The resolution of the regional, nested ocean model is approximately 0.2 degrees compared to the 1 degree resolution of the global ocean model within which it is embedded and this work complements previously published work on ocean circulation and marine heatwaves using the New Zealand Earth System Model, NZESM. After a discussion of the eddy-permitting capability of the nested ocean and its coupling to the overlaying atmosphere, we study the effects on air temperature, precipitation and evaporation, latent and sensible surface heat balances, zonal and meridional winds, the anticyclonic storm track and the effect on clouds. With respect to clouds, we show that stratocumulus is found to be the most sensitive cloud type when partitioning the results by cloud-top-pressure and optical depth. Overall we find that the NZESM provides a better representation of regional atmospheric climate compared to its parent model - the UKESM - although this improvement is not universal. For example, although the NZESM shows better agreement in surface air temperature within the nested ocean region, there is also some deterioration in the agreement compared to the UKESM at high southern latitudes where the seasonal sea-ice edge coincides with a transition from negative to positive correlation between air temperature and cloud amount. The lack of additional model tuning in the NZESM after the nested ocean model's inclusion largely accounts for the presence of these improvement-deterioration pairs.
13 Feb 2023Submitted to ESS Open Archive
15 Feb 2023Published in ESS Open Archive