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| Titel |
Synoptic-scale zonal available potential energy increases in the Northern
Hemisphere |
| VerfasserIn |
Kevin Bowley, John Gyakum, Eyad Atallah |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138924
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| Publikation (Nr.) |
 EGU/EGU2017-2065.pdf |
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| Zusammenfassung |
| Available potential energy (APE), a measure of the energy available for conversion to kinetic
energy, has been previously applied to examine changes in baroclinic instability as
well as seasonal changes in the general circulation. Here, pathways in which the
troposphere can build the reservoir of zonal available potential energy (ZAPE)
on synoptic (3-10 day) time scales are explored. A climatology of ZAPE and its
associated generation and conversion terms are calculated from the National Centers
for Environmental Prediction (NCEP) Department of Energy (DOE) Reanalysis
2 global reanalysis dataset from 1979 to 2011 for the Northern Hemisphere (20˚
-85˚ N). Applying a standardized-anomaly based identification technique, 160
ZAPE buildup events are identified during the 33-year period, which are grouped by
meteorological season and the amplitude of the ZAPE anomaly at the conclusion of a buildup
period.
Buildup events are analyzed from both an energetics framework and a dynamical
framework to identify key processes contributing toward increases in ZAPE. Anomalously
low conversion of ZAPE to eddy APE (CA) and anomalously high generation of ZAPE
(GZAPE) contribute equally to the total rate of change of ZAPE, while conversion from
ZAPE to zonal kinetic energy (CZ) contributes little across all seasons. Anomalously low CA
occurs for much of the Northern Hemisphere during buildup events with larger contributions
from portions of the storm tracks, owing to changes in the jet location near high terrain,
zonal elongations of the jet exit regions, and shifts in the jet stream in response to
subtropical ridging. Examination of DJF buildup events reveals that the pathway
toward ZAPE increase includes rapid high latitude cooling leading to increased
GZAPE, high-latitude cut-off anticyclones acting to reduce CA, mid-latitude Rossby
wave trains exciting transient ridges acting to reduce CA, and sub-tropical ridging
associated with anticyclonic wave breaks acting to increase GZAPE and decrease CA. |
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