 |
| Titel |
The importance of wave break events for synoptic-scale buildups of Northern
Hemisphere zonal available potential energy |
| VerfasserIn |
Kevin Bowley, Eyad Atallah, John Gyakum |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138925
|
| Publikation (Nr.) |
 EGU/EGU2017-2066.pdf |
|
|
|
|
|
| Zusammenfassung |
| Zonal available potential energy (ZAPE) is an estimate of the amount of potential energy in
the atmosphere available for conversion to kinetic energy, providing a good proxy
for the overall strength of the general circulation. Previous studies have estimated
total hemispheric ZAPE, ZAPE generation, and conversion to kinetic energy, and
proposed physical mechanisms to describe the annual ZAPE cycle as well as short term
(sub-seasonal to synoptic) APE depletion events. Large, short term modulations of ZAPE
have been shown to be associated with impactful weather events in the mid- and
high-latitudes, including severe cyclones and high-amplitude ridging and blocking
events
In this study, we examine the association of significant synoptic time-scale increases
in ZAPE with dynamic tropopause wave break events. ZAPE buildup events are
determined using a 1979-2011 daily Northern Hemisphere (20˚ -85˚ N) ZAPE
climatology calculated from the National Centers for Environmental Prediction
(NCEP) Department of Energy (DOE) Reanalysis 2 global reanalysis dataset in an
isobaric framework. To diagnose the importance of wave breaks in the troposphere,
we objectively identify wave breaks using potential temperature on the dynamic
tropopause, identifying and tracking both anti-cyclonic (LC1) and cyclonic (LC2)
wave breaks during the 1979-2011 period. Our results indicate that LC1 wave break
events in the equatorward jet exit regions appear to play an important role in ZAPE
buildup events. The formation of these anti-cyclonic wave break events result in the
development of statistically significant warm-core high pressure anomalies in these
regions, acting to reduce baroclinic conversions. We will further demonstrate that
changes in LC2 wave break activity in the climatological storm track during ZAPE
buildup events are indicative of notable changes to the regions of significant cyclone
activity, which are occurring in response to shifts and elongations of the jet stream. |
|
|
|
|
|
|