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| Titel |
Idealized simulations of sting jet cyclones |
| VerfasserIn |
L. H. Baker, S. L. Gray, P. A. Clark |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065954
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| Zusammenfassung |
| An idealized modeling study of sting-jet cyclones is presented. Sting jets are descending
mesoscale jets that occur in some extratropical cyclones and produce localized regions of
strong low-level winds in the frontal fracture region. Moist baroclinic lifecycle (LC1)
simulations are performed with modifications to produce cyclones resembling observed
sting-jet cyclones. Two jets exist in the control idealized cyclone that descend into the frontal
fracture region and result in strong winds near to the top of the boundary layer;
one of these satisfies the criteria for a sting jet, the other is associated with the
warm front. Sensitivity experiments show that both these jets are robust features.
The sting jet strength (measured by maximum low-level wind speed or descent
rate) increases with the cyclone growth rate; growth rate increases with increasing
basic-state zonal jet maximum or decreasing basic-state tropospheric static stability. The
two cyclones with the weakest basic-state static stability have by far the strongest
sting jets, with descent rates comparable to those observed. Evaporative cooling
contributes up to 20% of the descent rate in these sting jets compared with up to
4% in the other sting jets. Conditional symmetric instability (CSI) release in the
cloud head also contributes to the sting jet, although there is less extensive CSI than
in observed cases. The robustness of the sting jets suggests that they could occur
frequently in cyclones with frontal fracture; however, they are unlikely to be identified
unless momentum transport through the boundary layer leads to strong surface wind
gusts. |
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