Wave Breaking Events and their link to Rossby Wave Packets and
Atmospheric Blockings during Southern Hemisphere Summer
Abstract
Rossby Wave packets (RWPs) are atmospheric perturbations located at
upper levels in mid-latitudes which, in certain cases, terminate in
Rossby Wave Breaking (RWB) events. When sufficiently persistent and
spatially extended, these RWB events are synoptically identical to
atmospheric blockings, which are linked to heatwaves and droughts.
Thus, studying RWB events after RWPs propagation and their link with
blocking is key to enhance extreme weather events detection 10-30 days
in advance. Hence, here we assess (i) the occurrence of RWB
events after the propagation of RWPs, (ii) whether long-lived RWPs (RWPs
with a lifespan above 8 days, or LLRWPs) are linked to large-scale RWB
events that could form a blocking event, and (iii) the proportion of
blocking situations that occur near RWB events. To do so, we applied a
tracking algorithm to detect RWPs in the Southern Hemisphere during
summertime between 1979-2020, developed a wave breaking algorithm to
identify RWB events, and searched for blocking events with different
intensities. Results show that LLRWPs and the other RWPs displayed
large-scale RWB events around 40% of the time, and most RWB events in
both distributions last around 1-2 days, which is not long enough to
identify them as blocking situations. Nearly 17% of blockings have a
RWB event nearby, but barely 5% of blockings are linked to RWPs,
suggesting that propagating RWPs are not strongly linked to blocking
development. Lastly, large-scale RWB events associated with RWPs that
lasted less than 8 days are influenced by the Southern Annular Mode and
El Niño-Southern Oscillation.