The importance of diabatic processes for the dynamics of synoptic-scale extratropical weather systems

Classically, for extratropical weather systems the importance of diabatic effects such as surface fluxes, phase changes of water in clouds, and radiation, has been regarded as secondary compared to the dry dynamical processes. Research during recent decades has modified this view of the role of diabatic processes. A combination of complementary research approaches has revealed that the nonlinear dynamics of extratropical cyclones and upper-tropospheric Rossby waves is affected – in some cases strongly – by diabatic processes. Despite the violation of material potential vorticity (PV) conservation in the presence of diabatic processes, the concept of PV has been of utmost importance to identify and quantify the role of diabatic processes and to integrate their effects into the classical understanding based on dry dynamics.

This presentation will outline the rapid recent progress that has demonstrated how diabatic effects, in particular those related to cloud microphysics, can affect the structure, dynamics, and predictability of extratropical cyclones and Rossby waves. The development of sophisticated diagnostics, growing applications of the Lagrangian perspective, real-case and idealised numerical experiments, and dedicated field experiments have been fundamental to this progress. The presentation will conclude by highlighting important implications of this new understanding of the role of diabatic processes for the broader field of weather and climate dynamics, gaps and the prospects of future progress.