Stratospheric sudden warmings (SSWs) and polar vortex intensifications (PVIs) are extreme dynamica events of the polar winter atmosphere with remote influences on tropospheric circulation and climate at middle-to-high latitudes. SSWs are breakdowns of the polar vortex accompanied by anomalous polar warming. PVIs are conversely accompanied by polar cooling. In the Equatorial stratosphere, easterlies and westerlies fully encircling the globe are alternating, with an approximate periodicity of 28 months, e.g. the so-called Quasi-Biennial Oscillation (QBO), a leading mode of variability. The QBO is highly dependent on dynamical disturbances (waves) emerging from the troposphere. Moreover, the QBO influence on the tropospheric processes leading to its dynamical forcing is an open question. SSWs, PVIs and the QBO are manifestations of stratospheric dynamical variability at the planetary scale, yet it is unclear the direct and/or indirect impact of dynamical process at much smaller scales (e.g. gravity waves) on these large-scale phenomena.
The scale-interaction question on the role of gravity waves for the stratospheric circulation and its variability is the primary objective of my research. To gain a better understanding of the interaction between gravity waves and planetary scale dynamics is expected to advance the representation of the stratosphere in global models and consequently reduce the current uncertainty in the response of the large-scale stratospheric circulation to variability and change and improve the representation of the connection between the stratosphere and the Earth climate. The need to revisit dynamical scale-interaction in the stratosphere arises indeed from the many questions originated by current assessments of stratospheric tele-connection pathways connecting variability and change in the troposphere. Because of its focus on stratosphere-troposphere 2-way dynamical coupling, my research cuts across the AES-department by closely collaborating with the AES research groups, in particular the MUA and CMO groups, and reaches out to the land and ocean departments by organizing, jointly with AES/MUA & OES/DCP, quasi-bimonthly meetings (the “stratosphere and climate forum”) for the discussion of issues of stratospheric dynamics connected to the ocean, sea-ice and land components of the climate system.
At the international level, the group contributes to the DynVar and Gravity Waves activities of the World Climate Research Program (WCRP)’s Stratospheric Process and their Role in Climate (SPARC) project.