Abstract
Abstract. Analysing GPS radio occultation density profiles, we have recently pointed out a localised area of enhanced gravity wave (GW) activity and breaking in the lower stratosphere of the east Asian–northwestern Pacific (EA/NP) region. With a mechanistic model of the middle and upper atmosphere, experiments are performed to study the possible effect of such a localised GW breaking region on large-scale circulation and transport and, more generally, a possible influence of the spatial distribution of gravity wave activity on middle atmospheric dynamics.The results indicate the important role of the spatial distribution of GW activity for polar vortex stability, formation of planetary waves and for the strength and structure of zonal-mean residual circulation. Furthermore, a possible effect of a zonally asymmetric GW breaking in the longitudinal variability of the Brewer–Dobson circulation is analysed. Finally, consequences of our results for a variety of research topics (e.g. sudden stratospheric warming, atmospheric blocking, teleconnection patterns and a compensation mechanism between resolved and unresolved drag) are discussed.
Highlights
Consideration of gravity wave (GW)-related processes is necessary for a proper description and modelling of the middle (as reviewed comprehensively by Fritts and Alexander (2003) and upper atmospheric dynamics
Demirhan Bari et al (2013) found the 3-D structure of circulation in the middle atmosphere to be in good correspondence with tracer fields, especially in relation to the zonal wave-1 pattern observed in the stratosphere and mesosphere, their study did not give a comprehensive dynamical explanation of the discovered circulation structures
Similar structure of an Eulerian-mean vertical velocity field has been found by Shaw and Boos (2012) as a response to an artificial torque placed in the troposphere around 30◦ N. These results show that GWs can contribute to longitudinal variations in the Brewer–Dobson circulation (BDC) and the downwelling and upwelling patterns may be related with GWs
Summary
Consideration of gravity wave (GW)-related processes is necessary for a proper description and modelling of the middle (as reviewed comprehensively by Fritts and Alexander (2003) and upper atmospheric dynamics (see, e.g., the review by Smith, 2012). There is a wide recognition of dynamical links between the stratosphere and troposphere with a potential to significantly affect conditions at the surface (Haynes, 2005; Kidston et al, 2015). Demirhan Bari et al (2013) found the 3-D structure of circulation in the middle atmosphere to be in good correspondence with tracer fields, especially in relation to the zonal wave-1 pattern observed in the stratosphere and mesosphere, their study did not give a comprehensive dynamical explanation of the discovered circulation structures (enhanced downward branch of BDC over northeastern Asia, wave-1 pattern)
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