Special Seminar — Talia Tamarin-Brodsky (EAPS)

The intrinsic relation between cyclones, anticyclones, and Rossby Wave Breaking events

Rossby wave breaking events are related to extreme weather events such as heat waves and blockings. However, a basic understanding of the synoptic-scale dynamics involved with the wave breaking is still absent. Here we combine a storm-tracking technique with a wave-breaking detection algorithm, to highlight the fundamental relation between low-level weather systems and upper-level wave breaking events in the North Atlantic region. We find that Anticyclonic Wave Breaking events (AWBs) are associated with a low level anticyclone and a strong upper level ridge, which are both located in the anticyclonic side of the jet. In addition, two cyclones are often found to the NW and SE of the anticyclone, such that a splitted and tilted jet is generated. Wave breaking composites centered around the anticyclonesl show that during the life cycle of the breaking, the low pressure anomalies rotate in an anticyclonic manner around the anticyclone, such that there is a low pressure anomaly to the north of the anticyclone by the end of the life cycle. On the other hand, Cyclonic Breaking events (CWBs) are mostly associated with a low level cyclone and a strong upper level trough, which are both located in the cyclonic side of the jet. An additional anticyclone is often found to the NE of the cyclone, which contributes to the downstream tilt of the otherwise zonal and southward jet. Compositing the flow around the cyclones shows that during CWB, it is now the high-pressure anomalies that rotate in a cyclonic manner around the low pressure anomalies. In both cases, the life cycle involves a transition from high-frequency anomalies oriented in the zonal direction, to low-frequency anomalies which are meridionally oriented. A better understanding of the basic synoptic-scale dynamics leading to RWBs and how they interact with the lower-frequency flow can improve our understanding as well as prediction of weather regimes and extreme weather events.

Please contact Kayla Bauer at kbauer@mit.edu for more more information and Zoom password