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: Non-annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent . Geophys. Res. Lett. , 36 , L08502 , doi:10.1029/2009GL037524 . Turner , J. , T. Phillips , J. S. Hosking , G. J. Marshall , and A. Orr , 2013 : The Amundsen Sea low . Int. J. Climatol ., 33 , 1818 – 1829 . van den Broeke , M. R. , and N. P. M. van Lipzig , 2003 : Response of wintertime Antarctic temperatures to the
: Non-annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent . Geophys. Res. Lett. , 36 , L08502 , doi:10.1029/2009GL037524 . Turner , J. , T. Phillips , J. S. Hosking , G. J. Marshall , and A. Orr , 2013 : The Amundsen Sea low . Int. J. Climatol ., 33 , 1818 – 1829 . van den Broeke , M. R. , and N. P. M. van Lipzig , 2003 : Response of wintertime Antarctic temperatures to the
Abstract
In model cycle 35r3 (Cy35r3) of the ECMWF Integrated Forecast System (IFS), the momentum deposition from small-scale nonorographic gravity waves is parameterized by the Scinocca scheme, which uses hydrostatic nonrotational wave dynamics to describe the vertical evolution of a broad, constant, and isotropic spectrum of gravity waves emanating from the troposphere. The Cy35r3 middle atmosphere climate shows the following: (i) an improved representation of the zonal-mean circulation and temperature structure; (ii) a realistic parameterized gravity wave drag; (iii) a reasonable stationary planetary wave structure and stationary wave driving in July and an underestimate of the generation of stationary wave activity in the troposphere and stationary wave driving in January; (iv) an improved representation of the tropical variability of the stratospheric circulation, although the westerly phase of the semiannual oscillation is missing; and (v) a realistic horizontal distribution of momentum flux in the stratosphere. By contrast, the middle atmosphere climate is much too close to radiative equilibrium when the Scinocca scheme is replaced by Rayleigh friction, which was the standard method of parameterizing the effects of nonorographic gravity waves in the IFS prior to Cy35r3. Finally, there is a reduction in Cy35r3 short-range high-resolution forecast error in the upper stratosphere.
Abstract
In model cycle 35r3 (Cy35r3) of the ECMWF Integrated Forecast System (IFS), the momentum deposition from small-scale nonorographic gravity waves is parameterized by the Scinocca scheme, which uses hydrostatic nonrotational wave dynamics to describe the vertical evolution of a broad, constant, and isotropic spectrum of gravity waves emanating from the troposphere. The Cy35r3 middle atmosphere climate shows the following: (i) an improved representation of the zonal-mean circulation and temperature structure; (ii) a realistic parameterized gravity wave drag; (iii) a reasonable stationary planetary wave structure and stationary wave driving in July and an underestimate of the generation of stationary wave activity in the troposphere and stationary wave driving in January; (iv) an improved representation of the tropical variability of the stratospheric circulation, although the westerly phase of the semiannual oscillation is missing; and (v) a realistic horizontal distribution of momentum flux in the stratosphere. By contrast, the middle atmosphere climate is much too close to radiative equilibrium when the Scinocca scheme is replaced by Rayleigh friction, which was the standard method of parameterizing the effects of nonorographic gravity waves in the IFS prior to Cy35r3. Finally, there is a reduction in Cy35r3 short-range high-resolution forecast error in the upper stratosphere.
the stratosphere by means of radiative cooling, a number of modeling studies (e.g., Christiansen et al. 1997 ; Manzini et al. 2003 ; Li et al. 2010 ; McLandress et al. 2010 ; Orr et al. 2012 ) suggest that it can also lead to changes to dynamical heating of the polar stratosphere, which occurs when air associated with the downwelling part of the wave-driven Brewer–Dobson circulation is compressed and adiabatically heated. In a previous study ( Orr et al. 2012 ), the authors used momentum
the stratosphere by means of radiative cooling, a number of modeling studies (e.g., Christiansen et al. 1997 ; Manzini et al. 2003 ; Li et al. 2010 ; McLandress et al. 2010 ; Orr et al. 2012 ) suggest that it can also lead to changes to dynamical heating of the polar stratosphere, which occurs when air associated with the downwelling part of the wave-driven Brewer–Dobson circulation is compressed and adiabatically heated. In a previous study ( Orr et al. 2012 ), the authors used momentum
temperatures. Orr et al. (2004) proposed that the blocking effect of the peninsula orography (a mountain chain typically 1.5–2.0 km high) at lower levels increases with the strength of the westerly flow, causing the wind to veer and become more northerly, again leading to greater transport of relatively warm air along the western side of the peninsula. However, the authors of this last paper also suggested that beyond a critical threshold stronger westerlies are more likely to pass over the peninsula
temperatures. Orr et al. (2004) proposed that the blocking effect of the peninsula orography (a mountain chain typically 1.5–2.0 km high) at lower levels increases with the strength of the westerly flow, causing the wind to veer and become more northerly, again leading to greater transport of relatively warm air along the western side of the peninsula. However, the authors of this last paper also suggested that beyond a critical threshold stronger westerlies are more likely to pass over the peninsula
over or around the barrier. For the high latitude and elongated shape of the AP, the flow is typically blocked when the Froude number (Fr) < 0.5 (“blocked” conditions) and it passes over the barrier when Fr > 0.5 (“flow-over” conditions) ( Ólaffson 2000 ; Orr et al. 2008 , hereafter OR08 ). The Froude number is defined as Fr = u/(NH) , where u is the layer-averaged cross-barrier wind speed and N is the Brunt–Väisälä frequency. Orr et al. (2004) stressed the importance of flow blocking in
over or around the barrier. For the high latitude and elongated shape of the AP, the flow is typically blocked when the Froude number (Fr) < 0.5 (“blocked” conditions) and it passes over the barrier when Fr > 0.5 (“flow-over” conditions) ( Ólaffson 2000 ; Orr et al. 2008 , hereafter OR08 ). The Froude number is defined as Fr = u/(NH) , where u is the layer-averaged cross-barrier wind speed and N is the Brunt–Väisälä frequency. Orr et al. (2004) stressed the importance of flow blocking in
. Geophys. Res. Lett. , 36 , L08502 , doi:10.1029/2009GL037524 . Turner , J. , T. J. Bracegirdle , T. Phillips , G. J. Marshall , and J. S. Hosking , 2013a : An initial assessment of Antarctic sea ice extent in the CMIP5 models . J. Climate , 26 , 1473 – 1484 . Turner , J. , T. Phillips , J. S. Hosking , G. J. Marshall , and A. Orr , 2013b : The Amundsen Sea low. Int. J. Climatol., 33, 1818–1829. van Loon , H. , 1967 : The half-yearly oscillations in middle and
. Geophys. Res. Lett. , 36 , L08502 , doi:10.1029/2009GL037524 . Turner , J. , T. J. Bracegirdle , T. Phillips , G. J. Marshall , and J. S. Hosking , 2013a : An initial assessment of Antarctic sea ice extent in the CMIP5 models . J. Climate , 26 , 1473 – 1484 . Turner , J. , T. Phillips , J. S. Hosking , G. J. Marshall , and A. Orr , 2013b : The Amundsen Sea low. Int. J. Climatol., 33, 1818–1829. van Loon , H. , 1967 : The half-yearly oscillations in middle and
establish the analog position. REFERENCES Alexander , S. P. , A. Orr , S. Webster , and D. J. Murphy , 2017 : Observations and fine-scale model simulations of gravity waves over Davis, East Antarctica (69°S, 78°E) . J. Geophys. Res. Atmos. , 122 , 7355 – 7370 , https://doi.org/10.1002/2017JD026615 . 10.1002/2017JD026615 Anderson , P. S. , 1993 : Evidence for an Antarctic winter coastal polynya . Antarct. Sci. , 5 , 221 – 226 , https://doi.org/10.1017/S0954102093000288 . 10.1017/S
establish the analog position. REFERENCES Alexander , S. P. , A. Orr , S. Webster , and D. J. Murphy , 2017 : Observations and fine-scale model simulations of gravity waves over Davis, East Antarctica (69°S, 78°E) . J. Geophys. Res. Atmos. , 122 , 7355 – 7370 , https://doi.org/10.1002/2017JD026615 . 10.1002/2017JD026615 Anderson , P. S. , 1993 : Evidence for an Antarctic winter coastal polynya . Antarct. Sci. , 5 , 221 – 226 , https://doi.org/10.1017/S0954102093000288 . 10.1017/S
surface melting include foehn winds ( Orr et al. 2008 , 2021 ; Elvidge et al. 2016 ; Datta et al. 2019 ; Zou et al. 2021 ; Gilbert et al. 2022 ), katabatic winds ( Parish and Bromwich 1989 ; Bromwich et al. 1992 ; Coggins et al. 2014 ; Lenaerts et al. 2017 ; Heinemann et al. 2019 ), and barrier winds ( Orr et al. 2004 , 2014 ; Coggins et al. 2014 ). Foehn events especially are known to cause extreme temperature increases over a few hours, with temperature spikes in Antarctica of >10 K
surface melting include foehn winds ( Orr et al. 2008 , 2021 ; Elvidge et al. 2016 ; Datta et al. 2019 ; Zou et al. 2021 ; Gilbert et al. 2022 ), katabatic winds ( Parish and Bromwich 1989 ; Bromwich et al. 1992 ; Coggins et al. 2014 ; Lenaerts et al. 2017 ; Heinemann et al. 2019 ), and barrier winds ( Orr et al. 2004 , 2014 ; Coggins et al. 2014 ). Foehn events especially are known to cause extreme temperature increases over a few hours, with temperature spikes in Antarctica of >10 K
this century ( Orr et al. 2005 ) and they show how changes in the ability of marine organisms to calcify will affect the ecosystem is of great concern. The simulated variability in the SO surface Ω A suggests that interannual variability could also be used to investigate how ocean biota respond to the Ω A changes. Acknowledgments RJM would like to acknowledge the funding support from the Australian Climate Change Science Program and the CSIRO Wealth from Oceans Flagship. AL was financially
this century ( Orr et al. 2005 ) and they show how changes in the ability of marine organisms to calcify will affect the ecosystem is of great concern. The simulated variability in the SO surface Ω A suggests that interannual variability could also be used to investigate how ocean biota respond to the Ω A changes. Acknowledgments RJM would like to acknowledge the funding support from the Australian Climate Change Science Program and the CSIRO Wealth from Oceans Flagship. AL was financially
. 2014 ), as evidenced by a poleward shift of the HCE. Several factors are recognized to have influences on the poleward shift of HCE, such as the stratospheric ozone depletion (e.g., Son et al. 2009 , 2010 ; Polvani et al. 2011 ; Orr et al. 2012 ; Waugh et al. 2015 ), greenhouse gas emissions (e.g., Tao et al. 2016 ), anthropogenic aerosols (e.g., Allen et al. 2012 , 2014 ), and sea surface temperature (SST) changes (e.g., Adam et al. 2014 ; Allen et al. 2014 ). These factors can influence
. 2014 ), as evidenced by a poleward shift of the HCE. Several factors are recognized to have influences on the poleward shift of HCE, such as the stratospheric ozone depletion (e.g., Son et al. 2009 , 2010 ; Polvani et al. 2011 ; Orr et al. 2012 ; Waugh et al. 2015 ), greenhouse gas emissions (e.g., Tao et al. 2016 ), anthropogenic aerosols (e.g., Allen et al. 2012 , 2014 ), and sea surface temperature (SST) changes (e.g., Adam et al. 2014 ; Allen et al. 2014 ). These factors can influence
