The Effect of a Well-Resolved Stratosphere on Surface Climate: Differences between CMIP5 Simulations with High and Low Top Versions of the Met Office Climate Model

• Published in: Journal of Climate
• Main Authors: Hardiman, S, Butchart, N, Hinton, T, Osprey, S, Gray, L
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2016
• Subjects: Midwinter; Sea ice
• Online Access: https://doi.org/10.1175/JCLI-D-11-00579.1; https://ora.ox.ac.uk/objects/uuid:5dd966b1-042e-4a24-a3a6-03466a2fa3fb

The importance of using a general circulation model that includes a well-resolved stratosphere for climate simulations, and particularly the influence this has on surface climate, is investigated. High top model sim- ulations are run with the Met Office Unified Model for the Coupled Model Intercomparison Project Phase 5 (CMIP5). These simulations are compared to equivalent simulations run using a low top model differing only in vertical extent and vertical resolution above 15 km. The period 1960-2002 is analyzed and compared to observations and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis dataset. Long-term climatology, variability, and trends in surface temperature and sea ice, along with the variability of the annular mode index, are found to be insensitive to the addition of a well-resolved stratosphere. The inclusion of a well-resolved stratosphere, however, does improve the impact of atmospheric teleconnections on surface climate, in particular the response to El Niño-Southern Oscillation, the quasi-biennial oscillation, and midwinter stratospheric sudden warmings (i.e., zonal mean wind reversals in the middle stratosphere). Thus, including a well-represented stratosphere could improve climate simulation on intraseasonal to in- terannual time scales. © 2012 American Meteorological Society.