Northern Hemisphere stationary waves in future climate projections.

• The response of the atmospheric large-scale circulation to an enhanced greenhouse gas (GHG) forcing varies among coupled global climate model (CGCM) simulations. In this study, sixteen CGCM simulations of the response of the climate system to a 1% per year increase in the atmospheric CO2 concentration to quadrupling are analysed with focus on Northern Hemisphere winter. A common signal in fourteen out of sixteen simulations is an increased or unchanged stationary wave amplitude. A majority of the simulations may be categorised into one of three groups based on the GHG induced changes in the atmospheric stationary waves. The response of the zonal mean barotropic wind is similar within each group. 50% of the simulations belong to the first group which is categorised by a stationary wave with five waves encompassing the whole NH and a strengthening of the zonal mean barotropic wind. The second and third group, consisting of three and two simulations respectively, are characterised by a broadening and a northward shift of the zonal mean barotropic wind respectively. A linear model of barotropic vorticity is employed to study the importance of these mean flow changes to the stationary wave response. The linear calculations indicate that the GHG induced mean wind changes explain 50%, 4% and 37% of the stationary wave changes in each group respectively. Thus, for the majority of simulations the zonal mean wind changes do significantly explain the stationary wave response.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Klimatforskning (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Climate Research (hsv//eng)

Nyckelord

stationary waves

future climate

climate modelling

Climatology

Klimatologi

Publikations- och innehållstyp

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