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Coupled Mixed-Layer Aquaplanet Integrations

Coupled Mixed-Layer Aquaplanet Integrations. Steve Woolnough Julia Slingo, Brian Hoskins. Model Description. HadAM3 1D Mixed layer model KPP mixing scheme of Large et al. (1994) 200m domain 30 levels in the vertical Stretched grid to give ~1m resolution near the surface.

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Coupled Mixed-Layer Aquaplanet Integrations

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  1. Coupled Mixed-Layer Aquaplanet Integrations Steve Woolnough Julia Slingo, Brian Hoskins

  2. Model Description • HadAM3 • 1D Mixed layer model • KPP mixing scheme of Large et al. (1994) • 200m domain • 30 levels in the vertical • Stretched grid to give ~1m resolution near the surface

  3. Coupling Strategy • Fully coupled between 20N and 20S with relaxation to Qobs(29ºC) between 12.5º to 20º latitude with a relaxation time of 15days-120days • Coupling every 3hours or every 24 hours • Ocean transport term applied through out the depth of the mixed layer to balance heat fluxes from uncoupled integration

  4. Motivation • To invesitgate the role of ocean mixed layer processes and SST variability on the intraseasonal and diurnal variability of the model • Conclusion: Very little impact if any (in this configuration of the Aquaplanet)

  5. Climatology very similar to that of the uncoupled integration for both daily and 3hourly coupling

  6. Coupling with intraseasonal convection • Composited three types of convective anomaly • 10-100day bandpassed precipitation • Filtered for eastward and westward moving waves with wavenumbers 1-10 • Eastward moving equatorial anomalies (EqE) • Westward moving equatorial anomalies (EqW) • Westward moving anomalies centred at 5ºN (5NW)

  7. Conclusions • Aquaplanet HadAM3 doesn’t seem to be sensitive to coupling in the deep tropics • SST anomalies very small • Possibly related to basic state winds? • NB large SST anomalies can organize convection in HadAM3 (Woolnough et al. 2001) • Maybe some scope for interesting behaviour on longer timescales • Phase of SST anomalies sensitive to frequency of coupling

  8. Aquaplanet forced by intraseasonal SST anomalies (Woonlough et al. 2001) • Large precipitation response

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