Abrupt transitions for turbulent atmosphere and climate dynamics

In the past, the Earth and Jupiter atmospheres have experienced fast and drastic transitions, sometimes associated with abrupt climate changes. Some of these changes of turbulent attractors where not caused by external perturbations, but the result of internal variability. Studying such abrupt transitions, for fully turbulent atmosphere dynamics, requires new numerical and theoretical tools. I will present two examples of recent works and new approaches developed in order to study abrupt transitions. First, for Earth like atmospheres, I will discuss the conditions for abrupt transitions to climates with superrotating equatorial jets. I will explain the fluid mechanics mechanisms and parameters that determine whether such transitions are discontinuous or continuous. And second, I will explain the use of rare event algorithms and large deviation theory to study abrupt changes in Jupiter atmosphere, in the turbulent dynamics of either barotropic or two-layer models.