What Determines Wave Breaking Orientations during Blocking Events
Here's the work with Talia on Rossby Wave Breaking orientation changes and Blockings. I had an oral presetation at the stormtracks 2025 in Rosendal, Norway, hosted by University of Bergen. You can find my slides here。 Atmospheric blockings are synoptic-scale, subseasonal, high-pressure systems that stagnate the eastward propagation of mid-latitude jet streams and often drive weather extremes. Many blockings are associated with Rossby wave breaking events, identified by potential vorticity (PV) overturnings, yet the mechanisms governing the wave-breaking orientations (i.e., cyclonic, anticyclonic, or both) remain unclear. Moreover, the breaking orientation can evolve throughout the block lifecycle, often linked to block decay and large-scale weather regime shifts. Here we analyze blocking over the Euro-Atlantic region and adopt a PV perspective to decompose the time derivative of the low-frequency meridional PV gradient into different terms representing interactions across timescales. We separately examine block formation, maintenance, and decay, focusing on the wave-breaking dynamics involved in each stage. Understanding the block breaking orientation is crucial not only for improving block prediction and termination, but also for better anticipating associated weather extremes. A recent example is the wintertime anticyclonically breaking block over the Western United States, which contributes to the severe California wildfires but also to downstream cutoff lows in the Northeastern United States.